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Tuesday, May 7, 2013
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Bogdan Wojtsekhowski
[Host: Nilanga Liyanage]
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4:00 PM, Room 313
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Jefferson Lab |
| Physics Building |
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“Searches for a hidden sector photon” |
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Tuesday, April 30, 2013
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Doug Higinbotham
[Host: Blaine Norum]
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3:30 PM, Room 204
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Jefferson Lab |
| Physics Building |
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“Trying to Solve The 30 year old EMC Effect Puzzle” |
ABSTRACT:
| In 1983 the Europeon Muon Collaboration (EMC) published their deep inelastic scattering ratios that showed that partons in heavy nuclei do not behave the same a partons in light nuclei. Over the decades, much work has been done by both experimentalists and theorists to understand why. In 2009, Jefferson Lab provided a new clue to the cause with their light nuclei EMC effect data.
These new data pointed to the EMC effect being a local density effect instead of an average effect. Soon after this observation, a phenomenological link between nuclear short-range correlations and the EMC effect was made. This
seminar will review both the EMC effect and short-range correlation results and the link that has been made between these two seemingly unrelated experiments. |
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Tuesday, April 23, 2013
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Evie Downie
[Host: Blaine Norum]
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3:30 PM, Room 204
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The George Washington University |
| Physics Building |
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“The MUSE experiment: addressing the proton radius puzzle via elastic muon scattering” |
ABSTRACT:
| The MUSE experiment aims to provide key missing information in the quest to resolve the proton radius puzzle: the difference between the 0.88 fm proton radius measured in atomic hydrogen and ep elastic scattering experiments and the 0.84 fm radius measured in muonic hydrogen. Over the last three years since the puzzle emerged, none of the many attempts to find a solution have reached a universally accepted resolution. Possible solutions include novel beyond standard model physics, novel hadronic physics and issues and/or underestimated uncertainties in the ep scattering data.
Recently there have been high precision electron scattering experiments at Mainz and JLab, and further measurements are planned. A series of excitation spectrum measurements on light nuclei are planned at PSI. The MUSE experiment will open up a new line of experimental investigations by measuring elastic muon scattering on the proton at the PSI piM1 beamline.
MUSE will scatter a mixed muon/pion/electron beam on a liquid hydrogen target with a Q^2 range of approximately 0.002 - 0.08 GeV2. Measurements of both μ+ and μ- at multiple beam momenta will enable checks of systematics, determination of two-photon exchange effects and magnetic contributions, and a radius determination at a similar level of precision to existing ep scattering experiments. Simultaneous electron scattering will allow similar tests and a direct comparison of the two probes, providing an excellent test of lepton universality. The physics background, status, and plans for the experiment will be discussed. |
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Wednesday, April 10, 2013
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Chao Gu
[Host: Nilanga Liyanage]
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3:30 PM, Room 204
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University of Virginia |
| Physics Building |
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“A Measurement of g2p and the Longitudinal-Transverse Spin Polarizability” |
ABSTRACT:
| The proton spin-dependent structure function g2p in the resonance region has been measured in a recent experiment at Jefferson Lab in Hall A. A polarized electron beam of energy 1.157-3.349 GeV was incident on a transversely polarized NH3 target. An inclusive measurement at 5.69 deg was performed in order to determine the g2p structure function in the Q2 region of 0.02-0.20 GeV2. No measurement of this quantity has been conducted at such a low-Q2 range before. This experiment will allow us to test the Burkhardt-Cottingham sum rule at low Q2 and extract the generalized longitudinal-transverse spin polarizability δLT. Chiral Perturbation Theory (χPT) is expected to work in this kinematic region and this measurement of δLT will give a benchmark test to χPT calculations. In this talk, I will give describe to the experiment and show the latest progress of the on-going analysis. |
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Tuesday, April 9, 2013
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Ryan Duve
[Host: Blaine Norum]
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3:30 PM, Room 204
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University of Virginia |
| Physics Building |
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“The Upcoming GDH Sum Rule Measurement for the Deuteron” |
ABSTRACT:
| This talk will introduce the GDH Sum Rule for the deuteron and the technical hurdles involved in making a doubly polarized measurement via the photodisintegration process d(γ,n)p. Three experimental components, the Duke Free Electron Laser Laboratory, the frozen-spin target HiFrost, and the Blowfish detector array, will be discussed, as well as the motivation for measuring the GDH Sum Rule. |
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Thursday, March 28, 2013
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Michael Mayer
[Host: Donal Day]
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3:30 PM, Room 313
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Old Dominion University |
| Physics Building |
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“Beam-Target Double Spin Asymmetry in →d(→e, e′p)n” |
ABSTRACT:
| Using the CLAS detector at Jefferson Lab, double spin asymmetries (A||) for quasi-elastic electron
scattering off the deuteron have been measured at several beam energies. The data were collected
during the EG1 experiment, which scattered longitudinally polarized electrons with energies from 1.6 to 5.8 GeV off a longitudinally polarized cryogenic ND3 target. The double spin asymmetries were measured as a function of photon virtuality Q2 (0.13−3.17 (GeV/c)2), missing momentum (0.0−0.5 GeV/c), and the angle between the (inferred) “spectator” neutron and the momentum transfer direction (θnq). The results from EG1b are compared with a recent model that includes final state interactions using a complete parameterization of nucleon-nucleon scattering. I will discuss the results for the double spin asymmetry and compare them to this model as well as a simplified model using the plane wave impulse approximation. |
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Tuesday, March 19, 2013
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Roxanne Springer
[Host: Simonetta Liuti]
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3:30 PM, Room 204
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Duke University |
| Physics Building |
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“The X(3872) and characteristics of hadronic bound states in the charm and beauty sector” |
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Wednesday, March 13, 2013
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Jixie Zhang
[Host: Donal Day]
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3:30 PM, Room 313
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Jefferson Lab |
| Physics Building |
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“Differential cross sections for exclusive π ‾ electro-production from the neutron” |
ABSTRACT:
| Differential cross sections for exclusive π ‾ electro-production from the neutron
in the reaction e+d → e′+π ‾+p+pr have been measured over a broad kinematics range in the BoNuS experiment, where pr is the recoil proton. The experiment was performed using a radial time projection chamber (RTPC) and the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab Hall B. The RTPC detector was specially built to detect low energy recoil protons and had a valid momentum acceptance from 67 to 250 MeV/c. The differential cross sections for D(e, e′π ‾p)p have been extracted, with the proton detected either by CLAS or by the RTPC. The
structure functions σT + εσL, σLT and σTT were determined and will be presented in comparison with MAID and SAID predictions. |
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Monday, March 11, 2013
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Heghine Seraydaryan
[Host: Donal Day]
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3:30 PM, Room 313
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Jefferson Lab |
| Physics Building |
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“Phi meson photoproduction at CLAS” |
ABSTRACT:
| Phi meson photoproduction cross section in its neutral decay mode is measured for the reaction gamma p → p (KSKL). The experiment is performed with a tagged photon beam of energy 1.6 -3.6 GeV incident on a liquid hydrogen target of the CLAS at Thomas Jefferson National Accelerator Facility. The final state is identified via reconstruction of KS in the invariant mass of two oppositely charged pions and by requiring missing particle in the reaction gamma p → p KS X to be KL. Presented results significantly enlarge the existing data on phi meson photoproduction. These data, combined with the data from the charged decay mode, will help to constrain different mechanisms of the phi photoproduction. |
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Friday, March 8, 2013
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Marianna Gabrielyan
[Host: Donal Day]
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11:00 AM, Room 313
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Florida International University |
| Physics Building |
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“Measurement of the Induced Polarization of Lambda(1116) in Kaon Electroproduction with CLAS” |
ABSTRACT:
| The CLAS Collaboration is using the p(e, e'K+p)π− reaction to perform a measurement of the induced polarization of the electroproduced Λ(1116). The parity-violating weak decay of the Λ into pπ− (64%) allows extraction of the recoil polarization of the Λ. The present study uses the CEBAF Large Acceptance Spectrometer (CLAS) to detect the scattered electron, the kaon, and the decay proton. CLAS allows for a large kinematic acceptance in Q2 (0.8 ≤ Q2 ≤ 3.5 GeV2), W (1.6 ≤ W ≤ 3.0 GeV), as well as the kaon scattering angle. In this experiment a 5.499 GeV electron beam was incident upon an unpolarized liquid-hydrogen target. The goal is to map out the kinematic dependencies for this polarization observable to provide new constraints for theoretical models of the electromagnetic production of kaon-hyperon final states. Along with previously published photo- and electroproduction cross sections and polarization observables from CLAS, SAPHIR, and GRAAL, these data are needed in a coupled-channel analysis to identify previously unobserved s-channel resonances. |
ABSTRACT:
| Recent theories of dark matter predict A’ gauge bosons in the mass range of 0.01-10 GeV that
couple to charged fermions with a strength of α’/αΕΜ~ 10-4 of the photon or less. The DarkLight (Detecting A Resonance Kinematically with eLectrons Incident on a Gaseous Hydrogen Target) experiment intends to use the 1 MW 100 MeV electron beam at the Jefferson Lab Free Electron Laser incident on a 1019 H2/cm2 thick target to study the process e- + p -> e- + p +e- + e+. A dark force particle would show up as a narrow resonance in the radiated e+ - e- system. DarkLight
would explore the A’ mass region 10-100 MeV with sensitivity to couplings as low as a’/aEM ~10-7 with 1/ab of data. |
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Tuesday, February 5, 2013
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Guy Ron
[Host: Blaine Norum]
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3:30 PM, Room 204
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Racah Institute of Physics, Hebrew University of Jerusalem |
| Physics Building |
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“Electrostatic Traps as a High Precision Measurement Tool” |
ABSTRACT:
Using principles analogous to those of conventional optics it is possible to construct fully electrostatic ion traps which act as a resonant cavity for ion beams. Such traps exhibit an unexpected phenomenon of self-bunching which allows for long lifetimes of trapped ion bunches.
I will present the principles and design of one such electrostatic trap, originally designed at the Weizmann Institute. I will further discuss the experimental possibilities aff orded by such a trap, with emphasis on mass spectroscopy and possible measurements of β decay correlations of trapped radioactive ions. Such measurements allow the study of possible standard model extensions affecting the structure of the weak interaction. |
ABSTRACT:
Two phenomena have been observed recently in experiments with slow neutrons: quantum states of ultracold neutrons (UCN) in the Earth’s gravitational field [1] and quantum states of cold neutrons (CN) in the centrifugal potential in the vicinity of a curved mirror [2]. The first experiment presented the first observation of quantum states of matter in a gravitational field; the second one is also known as the neutron whispering gallery effect. They are related by common experimental methods used, by common mathematical description, but also by their applications in elementary particle physics, in quantum optics, in surface science [3]. It is curious that these experiments present the first direct demonstration of the weak equivalence principle for an object in a quantum state. Much more precise measurements of/with these phenomena are going to be performed in a recently constructed second-generation GRANIT spectrometer [4]. Analogous experiments could be probably performed in future with anti-matter atoms [5-6], with interesting applications in various domains of science.
1. V.V. Nesvizhevsky et al, Nature 415, 297 (2002); S. Baessler et al, J. Phys. G 36, 10 (2009).
2. V.V. Nesvizhevsky et al, Nature Phys. 6, 114 (2010).
3. V.V. Nesvizhevsky, Phys.-Uspekhi 53, 645 (2010).
4. S. Baessler et al, Compt. Rend. Phys. 12, 707 (2011)
5. A.Yu. Voronin et al, Phys. Rev. A 83, 032903 (2011).
6. A.Yu. Voronin et al, Phys. Rev. A 85, 014902 (2012). |
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Tuesday, December 18, 2012
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Peng Peng
[Host: Blaine Norum]
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3:30 PM, Room 204
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University of Virginia |
| Physics Building |
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“Pseudoscalar meson photo-production from a polarized HD target for the study of N* spectrum” |
ABSTRACT:
| A complete characterization of the spectrum of N and Delta resonances is essential to understand the internal structure of the nucleon. Although the Constituent Quark Models(CQM) gives good predictions for resonances in low-energy region(less than 1.8 GeV). For mass states above 1.8 GeV, many of them have not been found in experiment. This discrepancy between theory and experiment can be attributed to two reasons. One reason is that most identified resonances were discovered in piN scattering; thus, the states that couple weakly to this channel will not be seen. Another reason is that the resonances are both broad and overlapping, which make them hard to identify. The photon production of pseudoscalar mesons studied in the G14 experiment gives us a chance to look at the decay channels in pi-pi-N, eta-N, K-Lamda, etc. Moreover the use of polarized beam, polarized targets, and the detection of the polarized recoil nucleon allow us to measure a large number of polarization observables. These observables will help removing the ambiguities in determining the multipoles in partial wave analysis for the identification of the undiscovered nucleon resonances. |
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Tuesday, December 4, 2012
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Evan Askanazi
[Host: Simonetta Liuti]
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3:30 PM, Room 204
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University of Virginia |
| Physics Building |
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“Self Organizing Maps for Extracting Deep Inelastic Scattering Observables” |
Nuclear/Particle Physics Seminar
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Tuesday, November 20, 2012
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Ted Rogers
[Host: Simonetta Liuti]
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3:30 PM, Room 204
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Stony Brook University |
| Physics Building |
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“TMD-Factorization with Evolution” |
ABSTRACT:
I will discuss applications of perturbative QCD to the study of inclusive processes that are sensitive to the intrinsic transverse motion of bound state constituents of hadrons. Transverse momentum dependent (TMD) factorization is the theoretical framework that is needed to address these processes in perturbation theory.
Factorization refers to the separation of short-distance (hard) physics, which is calculable in perturbative QCD, from the large-distance non-perturbative effects inside the transverse momentum dependent parton distribution and fragmentation functions.
I will summarize recent theoretical developments in TMD-factorization, and discuss current efforts to apply TMD-factorization phenomenologically to extract information about hadron structure. |
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Tuesday, May 1, 2012
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Reserved for HEP seminar
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3:30 PM, Room 204
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| Physics Building |
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Tuesday, April 17, 2012
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Kiadtisak Saenboonruang
[Host: Nilanga Liyanage]
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3:30 PM, Room 204
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UVA |
| Physics Building |
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“Precision Parity-Violating Measurement of the Neutron Skin of Lead” |
ABSTRACT:
| A measurement of a non-zero electric dipole moment of the neutron would have implications on our understanding of the Standard Model and the matter-antimatter asymmetry in the present universe. In 1994 Golub and Lamoreaux (Physics Reports 237, 1—62 (1994)) proposed a new measurement strategy that makes use of several unusual properties of liquid helium. A collaboration of 19 US research groups is now pursuing R&D for an experiment to be installed at the Spallation Neutron Source at ORNL. The talk will outline the features and significance of this measurement, and then focus on the cryogenic challenges of the experiment. |
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Tuesday, February 28, 2012
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Donald Jones
[Host: Kent Paschke]
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3:30 PM, Room 204
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University of Virginia |
| Physics Building |
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“Precision Compton Electron Beam Polarimetry for the Qweak Experiment” |
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Tuesday, December 13, 2011
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Martin Lehman
[Host: Dinko Pocanic]
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3:30 PM, Room 313
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University of Virginia |
| Physics Building |
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“Precise Measurement of the π → e υ Branching Ratio” |
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Wednesday, December 7, 2011
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Chueng-Ryong Ji
[Host: Simonetta Liuti]
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1:00 PM, Room 204
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North Carolina State University |
| Physics Building |
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“Kinematic Issue of GPDs in DVCS” |
ABSTRACT:
| Generalized Parton Distributions (GPDs) in Deeply Virtual Compton Scattering (DVCS) have been widely recognized and used as a useful tool to explore the quark and gluon structure of the target hadrons. However, we recently pointed out treacherous kinematic issue in analyzing DVCS in terms of GPDs. In this talk, we present our key findings in the simplest possible level of complete amplitude including the lepton current. Implication in the Jefferson Lab experiment of DVCS will also be discussed. |
ABSTRACT:
| Among the most exciting discoveries about the Quark-Gluon Plasma State is its extraordinary opacity to color-charged objects (quarks and gluons). This property, while facilitating rapid equilibration of the plasma, hides the state at the earliest times from direct measurement. Colorless probes (direct real and virtual photons) provide access to the earliest time scales, but suffer from huge backgrounds of electromagnetic decays of light mesons. In this seminar, we'll explore how the mass of virtual photons can be used to reduce background from light mesons and provide access to the direct plasma "shine" from the earliest times. |
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Tuesday, November 15, 2011
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Yousef Makdisi
[Host: D. G. Crabb]
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3:30 PM, Room 204
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Brookhaven National Laboratory |
| Physics Building |
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“Spin Physics at RHIC: Recent results and future prospects” |
ABSTRACT:
| The availability of polarized proton beams at RHIC opened a window to an unexplored kinematic region up to a center of mass energy of 500 GeV for elastic and diffractive proton-proton scattering.
Besides the measurement of the total scattering cross section, the polarization of the protons leads to a single spin asymmetry $A_N$, arising from an interference between the electromagnetic proton spin-flip and the hadronic non-flip scattering amplitudes.
The measurement is sensitive enough to detect a possible hadronic spin-flip contribution, which cannot be ruled out by the available data.
Detailed theoretical model calculations are also available for the double spin asymmetries $A_{NN}$ and $A_{SS}$, assuming varying magnitudes of an Odderon contribution to the scattering amplitude, which we will be able to distinguish at the 5\% level.
The Odderon is the hypothetical charge and parity odd partner of the dominant Pomeron.
Preliminary data from RHIC run 09 taken with the STAR detector will be shown. |
Special Nuclear Seminar
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Thursday, June 9, 2011
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Bob Golub
[Host: Stefan Baessler]
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11:00 AM, Room 313
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North Carolina State University |
| Physics Building |
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“Selected topics in searching for a neutron edm” |
ABSTRACT:
| A non-zero value of the neutron electric dipole moment (nedm) would represent a violation of T reversal and would be strong evidence for new physics beyond the standard model. After presenting an overview of the project and the experimental methods that are being designed into the search for a neutron edm that is foreseen to be carried out at the Oak Ridge Spallation neutron source (SNS) we discuss a newly discovered systematic error and efforts to deal with it. |
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Tuesday, May 10, 2011
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Diancheng Wang
[Host: Xiaochao Zheng]
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3:30 PM, Room 204
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UVa |
| Physics Building |
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“Parity Violating Deep Inelastic Scattering (PVDIS) at JLab 6 GeV” |
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Tuesday, May 3, 2011
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Dr. Annalisa D'Angelo
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3:30 PM, Room 204
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University of Rome (La Sapienza) |
| Physics Building |
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“Results from the GRAAL experiment” |
ABSTRACT:
| The GRAAL experiment was located at the European Synchrotron Radiation Facility (ESRF) in Grenoble (France). It consisted of a Compton backscattered polarized photon beam, of 1.5 GeV maximum energy, and a large solid angle detector (LAGRANgE), optimized for neutral particle detection. Over more than ten years of activity has provided photon beam asymmetry measurements of pseudo-scalar meson photo-production reactions on both proton and neutron targets, providing strong constraints to models that allow for the extraction of nucleon resonances properties from experimental results. Highlights from published data are summarized and the latest results on omega meson photo-production are presented |
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Tuesday, April 19, 2011
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Zongyi Gong
[Host: Mark Williams]
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3:30 PM, Room 204
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University of Virginia |
| Physics Building |
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“Molecular Breast Imaging Tomosynthesis” |
ABSTRACT:
| In 2-D Mammography, breast tissues are superimposed in single projection image thereby possibly masking small cancer. X-ray breast tomosynthesis (XBT) is a technique for reducing this problem by providing a 3-D image. However, it still provides only anatomic (structural) information. Since cancerous and harmless breast masses (lesions) often have similar structures, distinguishing them using structural imaging alone is difficult. The task of distinguishing between benign and malignant breast lesions can be significantly aided by taking advantage of the differences in their biological (functional) characteristics. Molecular breast imaging (MBI) is a recent technique that uses intravenously injected compounds (tracers) that are taken up to a much greater degree by malignant lesions than benign ones. By attaching a radioisotope atom to these tracer molecules they can give off a signal that can be detected by specially designed cameras placed near the breast. These cameras permit functional imaging of the entire breast and have resulted in reliable detection of tumors less than 1 cm in size. Nevertheless, similar to Mammography, the 2-D nature of MBI prevents any depth information of lesions from being obtainable. Moreover, the correction for gamma signal attenuation through the breast is virtually impossible in MBI. Our group is developing a unique dual modality tomographic (DMT) breast scanner that combines x-ray tomosynthesis and 3-D MBI tomosynthesis (MBIT) on a single integrated gantry. This talk will focus on the functional part. Specifically, image acquisition, reconstruction and restoration in MBIT will be covered. |
Joint HEP/Nuclear Seminar
ABSTRACT:
| Hydrodynamics is the universal theory describing the behavior of fluids when their spacetime variation is on scales longer than any microphysical scale in the fluid. Relativistic hydro has applications in heavy ion collisions and early Universe cosmology, and has seen a surge of interest due to heavy ion experiments and theoretical developments in AdS/CFT. I will explain what second order hydrodynamics is and why it is the minimum theory to study in the relativistic case.
Then I discuss some limitations of the theory, including a new bound on how small the viscosity can be and a complication in the rigorous definition of the viscous relaxation time τπ.
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ABSTRACT:
| The bare mass of the three valance quarks only makes up ~ 1% of the proton mass, the rest is a sea of gluons, quarks and anti-quarks, which is dominated by the up, down and strange quarks. From the quark model, one might naively expect that the electromagnetic form factors are determined only by the valence quarks, with no contribution from the strange sea quarks. But, existing data suggesting a non-zero strange quark contribution to these form factors at high Q2 has been a topic of great interest. A new measurement of the strange quark vector form factors by the HAPPEX III collaboration is discussed. |
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Tuesday, February 8, 2011
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Special Colloquium
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3:30 PM, Room 204
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| Physics Building |
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Tuesday, February 1, 2011
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Reserved for AMO Seminar
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3:30 PM, Room 204
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| Physics Building |
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ABSTRACT:
| The elastic electromagnetic form factors of the nucleon are among the most important observables characterizing its structure. Accurate knowledge of the proton form factors at large momentum transfers is required to test predictions of perturbative QCD, to constrain the nucleon Generalized Parton Distributions (GPDs), and to determine the nucleon's model-independent transverse charge and magnetization densities at small impact parameters. Through their relationship to GPDs, the nucleon form factors are also relevant to the nucleon spin puzzle, helping to evaluate Ji's angular momentum sum rule. In this seminar, I will present and discuss the results of recent recoil polarization measurements of the proton electric-to-magnetic form factor ratio. These results extend the momentum transfer reach of the method to Q2=8.5 GeV2, an increase of more than 50%. Additionally, our precise measurements at Q2=2.5 GeV2 will constrain models of multi-photon exchange effects believed responsible for the discrepancy between the Rosenbluth and polarization experiments. |
ABSTRACT:
| One of the longstanding unsolved problem in the nuclear physics is that of the nucleon
resonances N* and Δ*. The lifetime of these intermediate states is very short since they
decay strongly. Their parameters, mass, width, and coupling constants to various decay
modes are not well known. To solve this problem, double polarization experiments are
considered to be a very effective tool. I will present the preliminary result of the helicity
asymmetry “E” for γp → π 0 p channel from the first double polarization experiment at
Jefferson Lab and compare this result with the prediction of theoretical models. |
ABSTRACT:
| The quest for an understanding of the internal dynamics of the most fundamental systems in nature, the Hadron, continues. The theory of Quantum Chromodynamics, developed to describe these systems, explains many of the interactions which occur in the Hadron. This theory however cannot presently be solved analytically in the low-energy regime, the realm of non-perturbative QCD. Therefore in the place of these solutions, models of the baryon are used which treat the baryon as a system of three constituent quarks. These models however predict an excited baryon spectrum that has a higher density of states than that which has been observed experimentally. This is the so-called “missing resonance” problem. With the ultimate goal of finding evidence for the existence (or non-existence) of these resonances, quantities called “polarization observables” can be measured. These quantities which occur when the constraint of polarization is imposed on the reactions are highly sensitive to resonance production. In recent years, both single- and double-polarization experiments have been carried out at Jefferson Lab in Newport News, Virginia with the goal of resolving this missing resonance problem. One such polarized photoproduction experiment used linearly polarized photons incident on an unpolarized LH2 target. The analysis of a double meson final state from this polarized photoproduction data utilizing the power of a kinematic fitter has the ability to make highly accurate measurements of these observables. The analysis of γ p → p π + π - reactions and the extraction of two such observables, Is and Ic, is discussed. |
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Tuesday, September 14, 2010
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Deborah Steva & Greg Payne
[Host: Blaine Norum]
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3:30 PM, Room 204
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UVA Office of Environmental Health and Safety |
| Physics Building |
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“Radiation Safety Training” |
ABSTRACT:
| All personnel who might want to use radioactive sources or other radioactive material, or want to work in areas where such materials are used, are required to obtain certification from the Office of Environmental Health and Safety. Deborah and Greg will present the required Radiation Safety Training Course leading to this certification.
Anyone who may want to use radioactive material or work in an area where such material is used should attend this course.
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Tuesday, April 20, 2010
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Nick Kvaltine
[Host: Don Crabb]
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3:30 PM, Room 204
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University of Virginia |
| Physics Building |
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“DVCS on the Deuteron” |
ABSTRACT:
| The equivalence principle (EP) states that in a uniform gravitational field all bodies fall with the same acceleration regardless of their mass and internal structure. The equivalence principle is the underlying foundation of General Relativity, our current theory of gravity. Despite the fact that General Relativity has passed many precision experimental tests, it is fundamentally incompatible with the quantum nature of the standard model. Modern theories, like string theory and quantum gravity, predict violations of the equivalence principle.
In the experiments conducted at the University of Washington a composition dipole is suspended from a thin fiber in a vacuum vessel that rotates with constant rate. A violation of the equivalence principle would yield to a differential acceleration of the two materials to a source mass located to the side of this torsion balance.
Any differential acceleration can be detected as a sinusoidal excursion of the torsion pendulum at the rotation period. In this talk I will present measurements of the differential acceleration with an uncertainty of 3 fm/s2. These measurements set new limits on equivalence principle violating interactions between the composition dipole and a variety of sources.
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Thursday, April 8, 2010
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Peter Steinberg
[Host: Donal Day]
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2:00 PM, Room 313
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Brookhaven National Lab |
| Physics Building |
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“Recent results from the Relativistic Heavy Ion > Collider, and prospects for the LHC” |
ABSTRACT:
| Double spin asymmetries for the proton and the deuteron have been
measured in the EG1b experiment using the CLAS detector at Jefferson
Lab. Longitudinally polarized electrons at energies 1.6, 2.5, 4.2 and 5.7
GeV were scattered from longitudinally polarized NH 3 and ND 3 targets.
The double spin asymmetry Ak has been extracted from these data as a
function of Q 2 and W with unprecedented precision. The virtual photon
asymmetry A 1 and the spin structure function g 1 can be calculated from
these measurements by using parameterizations to the world data for the
virtual photon asymmetry A 2 and the unpolarized structure functions
F 1 and R. The large kinematic coverage of the experiment (0.05 GeV 2
< Q 2 < 5.0 GeV 2 and 1.08 GeV < W < 3.0 GeV) helps us to better
understand the spin structure of the nucleon, especially in the transition
region between hadronic and quark-gluon degrees of freedom. The results
from EG1b combined with other experiments provide a good description of
the virtual photon asymmetries making their parameterizations possible
in a large kinematic range. In this talk, the results on A 1 , g 1 and the first
moment Γ 1 1
of the deuteron will be presented. The parametrization efforts
on the asymmetries and the spin structure functions will be discussed. The
neutron spin structure function, extracted from the combined proton and
deuteron data, will be shown. |
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Tuesday, January 26, 2010
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Nadia Fomin
[Host: Donal Day]
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3:30 PM, Room 204
|
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University of Tennessee |
| Physics Building |
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“The NPDGamma experiment - Probing the hadronic weak interaction through a measurement of parity violation in polarized cold neutron capture” |
ABSTRACT:
| The NPDGamma experiment aims to measure the correlation between the neutron spin and the direction of the emitted photon in neutron-proton capture. A parity violating asymmetry from this process can be directly related to the strength of the hadronic weak interaction between nucleons.
The first phase of the experiment was completed in 2006 at LANSCE.
The methodology will be discussed and preliminary results will be presented. The next run will start in early 2010 at the SNS at ORNL with several improvements, which will be discussed. The upcoming run will yield a measurement with a projected statistical error 1x10 -8 . This will allow the results to be compared meaningfully with theoretical predictions
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Tuesday, November 24, 2009
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OLIVER JAHN
[Host: Blaine Norum]
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3:00 PM, Room 313
|
|
University of Mainz |
| Physics Building |
|
“The GDH Experiment at MAMI” |
ABSTRACT:
| The GDH sum rule connects ground state properties of the nucleon with helicity-dependent cross sections. To investigate these cross sections on the deuteron, experiments have been carried out by the A2-Collaboration at the Mainz Microtron (Germany) in 1998 and in 2003, using circularly polarized photons on a polarized d-butanol target. The latest analysis results and the status of the GDH experiment with the Crystal Ball detector are reported.
|
ABSTRACT:
| This is the only Jefferson Lab polarized 3He experiment which is seeking to better understand the 3He system, as opposed to using it as an effective neutron target, by measuring double-polarized asymmetries in the 3He(e,e'd) reaction which are believed to be a probe particularly sensitive to the details of the 3He system. Major theoretical advances have been made in the Faddeev calculations of the Bochum/Krakow and Hannover groups, resulting in quite distinct descriptions of these observables. This development has important implications for experiments using 3He as an effective neutron target. |
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Tuesday, April 7, 2009
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Reserved for CM Seminar
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3:30 PM, Room 204
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|
|
| Physics Building |
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Tuesday, March 31, 2009
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Lisa Kaufman
[Host: Kent Paschke ]
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3:30 PM, Room 204
|
|
University of Maryland |
| Physics Building |
|
“Searching for Double Beta Decay with the Enriched Xenon Observatory” |
ABSTRACT:
| An observation of neutrinoless double beta decay would have significant impact on our understanding of the lepton sector of the Standard Model. First, neutrinoless double beta decay could shed light on the absolute mass scale of the neutrino mass spectrum, a quantity which cannot be constrained by neutrino oscillation experiments. Second, double beta decay is only allowed if the neutrino and anti-neutrino are identical which is a basic prediction of many extensions of the Standard Model including many grand unified theories. The Enriched Xenon Observatory (EXO) is developing sensitive searches of double beta decay using Xenon-136. The first phase of the experiment, called EXO-200, is in the final stages of assembly in the WIPP underground facility in Carlsbad, NM and will be by far the largest double beta decay experiment ever attempted. The current status of the EXO-200 experiment will be presented. |
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Tuesday, March 24, 2009
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|
Meifeng Lin
[Host: Chris Dawson]
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|
3:30 PM, Room 204
|
|
MIT |
| Physics Building |
|
“Nucleon Form Factors from Lattice QCD” |
ABSTRACT:
| First-principles calculations of the nucleon form factors and generalized form factors have been made possible by employing the lattice QCD techniques. Together with the experimental efforts, lattice results for the nucleon form factors have deepened our understanding of the internal structure of the nucleon, such as the charge and current distributions, and the spin decomposition of the nucleon. In this talk, I will present some recent lattice QCD results for the nucleon form factors using a five-dimensional chirally symmetric fermion action. I will also address some challenges faced by modern lattice form factor calculations.
|
ABSTRACT:
| The muon group at Illinois is performing three experiments at the Paul Scherrer Institute all measuring the muon lifetime with high precision. The MuLan experiment uses a simple soccer-ball like scintillator array to detect the decay positrons. We collected twice 10 12 muon decays in two different target materials to obtain the final precision of 1 ppm which will give a 20 times better determination of the Fermi constant G F . A first result was recently published [1] which already improved the precision of G F to 5 ppm. The muon capture experiment MuCap uses a negative muon beam stopped in a time projection chamber as an active target filled with ultra-pure hydrogen gas. The elementary capture process μ - +p → n+ ν offers a rare (0.15%) but additional disappearance channel. The measured difference of the positive and negative muon's lifetime determines the rate of the capture process to a final precision of 1%. This can be used to derive an improved value of the proton's pseudoscalar form factor g P to 7% precision. A first result gP = 7.3 1.1 has been published [2]. This is a first precise, unambigous determintation of gP and an important test of QCD symmetries. Recently, we started a new experiment, MuSun [3], that will start a first commissioning run at the end of 2008. Here, a measurement of the μ - +d → n+n+ ν provides a benchmark of the understanding of weak processes in the two nucleon-system. It was shown, that other weak reactions involving the two nucleon system (pp → de + ν or ν +d reactions) are related to the same low-energy constant, characterizing the two nucleon system at short distances. This constant is not well constrained and therefore the MuSun experiment comes closest to calibrating these basic astrophysical reactions under terrestrial conditions.
[1] Phys. Rev. Lett. 99, 032001 (2007)
[2] Phys. Rev. Lett. 99, 032002 (2007)
[3] http://www.npl.uiuc.edu/exp/musun/documents/prop07.pdf
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Tuesday, March 17, 2009
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Reserved for CMP seminar
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3:30 PM, Room 204
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|
|
| Physics Building |
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Joint Nuclear and High Energy Seminar
ABSTRACT:
| The talk presents an overview and status report of the MEG experiment at PSI, Switzerland, which searches for the decay Mu -> e Gamma at the
10^(-13) level. The motivation for the experiment is discussed and compared with other Lepton Flavor Violating processes, such as Mu A -> eA conversion. To accommodate the extremely high demands regarding pile-up suppression, timing resolution, and versatility, a special waveform digitizing technique was designed and implemented in the MEG experiment. It relies on the Domino Ring Sampling chip (DRS), capable of digitizing 8 channels with 5 GHz and 12 bits effective resolution on a single radiation hard CMOS chip. The DRS chip is currently used in the MEG experiment to digitize 2000 drift chamber channels and 1000 photomultiplier channels, eliminating the need for traditional ADCs and TDCs. Techniques used in MEG for waveform processing (e.g., data compression, pulse shape discrimination, and crosstalk elimination) may have applications in other rare decay experiments, and in cosmic ray astronomy.
|
ABSTRACT:
| A new generation of ultra-precise measurements of parity-violation
(PV) effects in electron scattering at 12 GeV at JLab is being currently developed. These experiments will require an improvement in beam polarimetry accuracy, by a factor of 2 to 3 in comparison with the present most accurate measurements. I will present an outline of the planned PV experiments, describe the existing polarimetry methods, and discuss a proposal to improve considerably the accuracy of polarimetry based on Moller scattering. It is proposed to use polarized atomic hydrogen gas, stored in an ultra-cold magnetic trap, as the polarimeter target. Such a target of practically 100% polarized electrons could provide a systematic accuracy better than 0.5%.
Although such traps have been built for particle physics applications, the storage cell has not been used so far as the target in a high power beam. Possible impacts the CEBAF beam can make on such a target will be discussed, including heating by ionization losses and the impact of the beam electromagnetic (RF) radiation.
|
ABSTRACT:
|
Using a novel 4π detector the Nab collaboration intends to measure a, the electron-neutrino correlation parameter, and b, the Fierz interference term, in neutron beta decay. The Nab experiment will be conducted in the Fundamental Neutron Physics Beamline at the Spallation Neutron Source in Oak Ridge, TN. I will present the design and simulation of the Electro-Magnetic Spectrometer which will be used to confine the decay products and shepherd them to the detector.
|
ABSTRACT:
| The PEN experiment aims to measure the semileptonic decay π → eν(γ)(πe2 decay) branching ratio at PSI, with an ncertainty of ΔB/B∼5×10-4,or better, using a large-angle detector system featuring a pure CsI calorimeter. This experiment will give a stringent test of lepton universality. Preliminary results from a basic level analysis of data from the first two developmental runs will be discussed.
These results, coupled with a discussion of experimental techniques, such as the use of a segmented active degrader and target waveform digitization, will demonstrate our ability to control systematic uncertainties in the experiment.
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Tuesday, October 14, 2008
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|
D. Stamenov
[Host: D. G. Crabb]
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3:30 PM, Room 204
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Institute for Nuclear Research and Nuclear Energy, Bulgaria |
| Physics Building |
|
“Progress in the Determination of Polarized PDFs and Higher Twist” |
ABSTRACT:
| The impact of very precise CLAS and COMPASS g 1 /F 1 data on the polarized parton densities and higher twist effects is discussed. It is demonstrated that the inclusion of the low Q 2 CLAS data in the NLO QCD analysis of the world DIS data improves essentially our knowledge of HT corrections to g 1 and does not affect the central values of PDFs, while the large Q 2 COMPASS data influence mainly the strange quark and gluon polarizations, but practically do not change the HT corrections. The uncertainties in the determination of polarized parton densities are significantly reduced due to both of the data sets. These results strongly support the QCD framework, in which the leading twist NLO pQCD contribution is supplemented by higher twist terms of O(Λ 2 /Q 2 ). Different solutions for the polarized gluon density, as well as the present status of the proton sum rule are also discussed. |
ABSTRACT:
| Large branching fractions for hadronic B decays involving the eta^prime
(1997) and also in the B semileptonic decay to the eta^prime (2006) could potentially be caused by the extra 2-gluon couplings from the singlet component of the eta^prime meson. Now, for CLEO-C, we look to semileptonic decays of the D meson to the eta^prime to see if there is evidence for enhancement there as well. We make improvements to the “neutrino reconstruction” method used to study B decays, and find that the new algorithm can also be used to simultaneously measure a large number of D hadronic decays as well.
|
ABSTRACT:
| The Spin Asymmetry on the Nucleon Experiment (SANE) will employ a revolutionary increase in Figure of Merit to obtain precise gp2 and
Ap1 results at high Bjorken x. Using the highest available JLab beam energy, a 194 msr electromagnetic calorimeter will view the UVa polarized NH3 target at 8.5 times 10^34 proton luminosity. The large Bjorken x region provides an important view on proton structure where the sea quarks have been stripped away. Using measurements of these ``naked protons'' is crucial for the understanding of strong QCD and can provide a connection between experimentally measured moments of polarized structure functions and quark matrix elements calculated in lattice QCD.
The experiment is scheduled to begin installation in June, and will begin taking data in October, using JLab's 5.9 GeV polarized electron beam. We will discuss the physics motivation for SANE, as well as the current status of the preparations and expected results.
|
ABSTRACT:
| A Hybrid 3 He Polarizer is being constructed for use by the Center for InVivo Hyperpolarized Gas MR Imaging at the University of Virginia Health System. It will take advantage of the Hybrid Spin Exchange Optical Pumping, and it will be calibrated using a combination of Adiabatic Fast Passage NMR and Electron Paramagnetic Resonance. These techniques will be detailed, and the construction progress will be summarized. |
ABSTRACT:
| Hybrid spin exchange optical pumping consistently outperforms pure alkali SEOP. Hybrid cells contain an alloy of potassium and a small amount of rubidium, whereas conventional cells contain a single species of metal, typically Rb. K-3He spin exchange is more efficient than Rb-3He.
Consequently, less laser power is required to achieve a higher noble gas polarization with the benefit of a shorter polarization time. The hybrid technique has been successfully employed in the large scale production of target cells for use in nuclear physics experiments and shows great potential for use in medical imaging. The production of hybrid alloys, optimization, and results will be discussed.
|
ABSTRACT:
| The Low Energy Neutron Source at Indiana University is a University-based long-pulsed source that makes use of a coupled solid methane moderator operating at temperatures below 10K. I will present recent results in which the moderator performance is compared to the predictions from our recently developed model for methane dynamics in
the low temperature (Phase II). I will also present the UCN production
in solid oxygen involving magnon (spin wave) exchanges which is fundamentally different from the well-known phonon mechanism in solid deuterium.
|
ABSTRACT:
| The extrapolation of nucleon magnetic form factors calculated within lattice QCD is investigated within a framework based upon heavy baryon chiral effective-field theory. All one-loop graphs are considered at arbitrary momentum transfer and all octet and decuplet baryons are included in the intermediate states. Finite range regularisation is applied to improve the convergence in the quark-mass expansion.
The resulting values of the form factors at the physical pion mass are in good agreement with the experimental data.
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Tuesday, February 19, 2008
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Reserved for Colloquium
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3:30 PM, Room 204
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|
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| Physics Building |
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Monday, January 14, 2008
|
|
Anthony Palladino
[Host: Don Crabb]
|
|
3:30 PM, Room 204
|
|
University of Virginia |
| Physics Building |
|
“TBA” |
ABSTRACT:
| I will give an introduction to the pentaquarks, possible five quark baryons. Quantum Chromodynamics does not forbid existence of such a states, however experimental evidence for their existence is controversial. The whole sitation becomes even more complicated recently as some experiments claiming the discovery of pentaquarks did not see it in a repeated high statistics data set and therefore set up an upper limits for the cross section for the production of the Theta+ baryon on the order of a few nano barn. I will discuss this and also the possibility on how one can increase the sensitivity of the measurement using Quantum Mechanical interference with other strong production channels leading to the same final state.
|
ABSTRACT:
| The question after the individual parton (quarks and gluons) contributions
to the spin of the nucleon is even after 20 years of experimental efforts
not yet solved.
After several very precise measurements in polarized deep inelastic
scattering it is clear, that the spin of the nucleon can not be explained
by the contribution of the quarks alone. This is affirmed by the newest
results from COMPASS, HERMES and JLAB on the inclusive spin structure
function g1 and on the individual contributions from the different quark
flavors from semi-inclusive deep inelastic scattering data.
Recently COMPASS and HERMES have started to measure the gluon polarization
by isolating the photon gluon fusion process in semi-inclusive deep
inelastic scattering; latest results on the contribution of the gluons to
the nucleon spin from these measurements and RHIC will be discussed.
The clear experimental evidence of exclusive reactions, especially DVCS,
allows in the formalism of generalised parton distributions the study of
an other component of the nucleon spin the orbital angular momentum.
The most recent results on indications of the size of the orbital angular
momentum of quarks will be presented.
|
ABSTRACT:
| In 2003 new experimental evidence was presented for the observation of the exotic baryon Θ + (1540) with a minimal quark content $uudd\bar{s}$. Quickly more than ten nuclear and high energy physics experiments reported positive results, apparently confirming the existence of the Θ + (1540), but all suffered from low statistical precision. An increasing number of null results started to appear, seemingly in contradiction with the positive sightings. Now the null results dominate the positive results, often with impressive statistical precision, and cast doubt on the existence of the Θ + (1540). The experimental status will be discussed, including some recent positive results. The past contributions and ongoing efforts of the Hermes experiment will be highlighted. |
|
Tuesday, September 25, 2007
|
|
Tanja Horn
[Host: Donal Day]
|
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3:30 PM, Room 204
|
|
JLAB |
| Physics Building |
|
“The pion form factor” |
ABSTRACT:
| The pion charge form factor, F π , is the fundamental interest in the study of the quark-gluon structure of hadrons. The relatively simple < qq > valence structure makes the pion an ideal test case for all models of hadronic structure. Experimentally, the measurement of the pion form factor poses special challenges. The technique utilizes a precision Rosenbluth seperation of the p(e,e' π + )n reaction at low -t. F π is then extracted from the separated σ L cross sections with the aid of a model. Over the past several years, we have carried out two experiments at Jefferson Lab (JLab) to measure F π over a kinematic range of Q 2 = 0.6-2.45 GeV 2 . These measurements are planned to be extended to higher Q 2 with the completion of the JLab 12 GeV upgrade. These data would challenge QCD based calculations in the most rigorous manner. The recent JLab results will be presented and compared to a variety of model calculations, and the future outlook will be discussed.
|
Special Colloquium
ABSTRACT:
| Although Quantum Chromodynamics (QCD) is the acclaimed theory of the strong interactions,
important longstanding questions still remain to be answered
on the nature of confinement of quarks and gluons inside the proton, and
on their dynamical contribution to the proton's mass and spin.
Deeply Virtual Compton Scattering (DVCS) and Exclusive Meson Production
provide alternative tools to purely inclusive reactions that have significantly
improved our studies of hadronic structure.
By allowing for an additional momentum transfer "t" to the proton
besides the large momentum transfered in the deep inelastic collision,
one can in principle
simultaneously access the longitudinal momentum fraction of the quarks
and their position inside the proton, providing 3D "images" of quarks in
hadrons.
The price one pays for the rich phenomenology accessible through DVCS
is a dramatic increase in complexity, due to the enlarged phase space
one needs to cover. A new approach is being developed based on Self-Organizing
Maps (SOMs), broadly related to Neural Networks, that allows for
extensive parameter searches and enables the user to directly control the data
selection procedure. Finally, among a wide range of recently studied implications,
the SOMs models are connected to complexity theory, leading to the
possibility of studying emergent behaviors in the system's properties.
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Tuesday, April 24, 2007
|
|
Mitra Shabestari
[Host: Donal Day]
|
|
3:30 PM, Room 204
|
|
University of Virginia |
| Physics Building |
|
“A Precision Measurement to Test Chiral QCD Dynamics” |
ABSTRACT:
| Experiment E04-007, in Hall A at Jefferson Lab, is a high precision measurement of the reaction P(e,e'P)π 0 from the threshold to 20MeV above, and Q 2 values between 0.04(GeV/c) 2 and 0.14(GeV/c) 2 . The near threshold cross sections are relatively small, which demand high resolution and as large acceptance as possible. Hall A, with the HRS and large acceptance BigBite spectrometer satisfies these requirements. I will talk about BigBite spectrometer, and also explain how the results of this experiment will provide a stringent test of chiral QCD. |
|
Tuesday, April 17, 2007
|
|
Michael Carl
[Host: Donal Day]
|
|
3:30 PM, Room 204
|
|
University of Virginia |
| Physics Building |
|
“Measurement of hyperpolarized gas diffusion at very short time scales” |
ABSTRACT:
| Hyperpolarized 3 He diffusion MRI is a powerful tool to probe lung microstructure at a length scale inaccessible by conventional k-space MRI. For short diffusion times, ∆, time dependent diffusion measurements are sensitive to the surface to volume ratio (S/V) of the surrounding structure. Because of the high gas diffusivity (D Xe =0.14cm 2 /s, D He =0.88cm 2 /s) and the small size of alveoli (~200μm), measurement of S/V with the traditional single bipolar diffusion technique is challenging in the lung, since only small diffusion attenuation can be imparted within the short time scale regime (~200μs). Given the significance of short time scale diffusion in the assessment of lung microstructure, we developed a new technique that proves promising to enable such measurements. |
Special Colloquium
|
Tuesday, April 10, 2007
|
|
Stefan Baessler
[Host: Blaine Norum]
|
|
3:30 PM, Room 204
|
|
Johannes Gutenberg Universitat Mainz (Germany) |
| Physics Building |
|
“Investigating Parity Violation in Neutron Decay ” |
ABSTRACT:
| Precision measurements in neutron decay allow to determine the coupling constants of weak interaction and to test aspects of the Standard Model of Elementary Particle Physics. This is achieved in measurements of the lifetime of the neutron and of several angular correlations in the decay. In my talk I will mainly report about the experiences and results we gained with the spectrometers PERKEO and aSPECT. |
ABSTRACT:
| The EG4 experiment at the Jefferson Lab (E12-06-109) studied the GDH (Gerasimov-Drell_Hearn) Sum Rule that relates the difference of the two photoabsorption cross-sections to the anomalous magnetic moment of the proton, deuteron and neutron in the real photon limit. In reality we try to approach the real photon limit by having the Q 2 very small. The experiment used a highly polarized electron beam and longitudinally polarized solid ammonia targets. The analysis to determine the deuteron target polarization using the data acquired from the NMR system will be shown with different analysis methods compared and further target polarization analysis via the scattering asymmetry method is also discussed.
|
ABSTRACT:
| Lattice QCD is a numerical method for solving the complicated dynamics
of QCD in the non-perturbative, low energy regime, allowing computations of the spectrum and strong
interactions of hadrons. To investigate the interactions of these hadrons with the remainder
of the Standard Model (leptons and the electro-weak gauge bosons) and physics beyond the
Standard Model, external operators must be included. This can be done by calculating hadron
matrix elements with explicit operator insertions and generally also using external field techniques.
In this second approach, the properties of hadrons are computed in an appropriate classical background
field (e.g., electroweak) and their modification from the zero external field case determines the quantity
of interest. I will discuss the advantages and disadvantages of this approach giving examples including
the electromagnetic and spin polarisabilities of hadrons and the nuclear modification of parton
distributions (the EMC effect). |
|
Tuesday, March 13, 2007
|
|
James Osborn
[Host: Hank Thacker]
|
|
3:30 PM, Room 204
|
|
Boston University |
| Physics Building |
|
“Localization transition in QCD at nonzero temperature” |
ABSTRACT:
| Over 20 years ago Diakanov and Petrov suggested that the chiral phase
transition in QCD might be similar to a metal-insulator transition
based on the instanton description of the QCD vacuum. The arguments,
however, are general and can be applied to other topological objects
as well. I will review the proposed connection between QCD and a
disordered medium and present some recent results from lattice QCD
that are consistent with a localization transition in the lowest
eigenmodes of the Dirac operator. |
|
Thursday, March 1, 2007
|
|
Diana Vaman
[Host: Hank Thacker]
|
|
4:00 PM, Room 204
|
|
University of Michigan |
| Physics Building |
|
“Holography with backreacted flavor” |
ABSTRACT:
| The gauge/string holographic duality has opened a new window into the
non-perturbative regime of gauge theories.
I will present the construction of supergravity duals to N=2 supersymmetric gauge theories coupled with matter (quarks) in the fundamental representation of the gauge group. The supergravity solutions are obtained by taking the decoupling limit of D3/D7 (color/flavor) brane systems.
The backreaction of the flavor branes needs to be accounted for, as it allows to go beyond the quenched approximation on the dual gauge theory side. I will give the spectrum of mesons (bound states of quark-anti quark pairs) and discuss the effect of the backreacted flavor.
Lastly, I will present the supergravity dual to the finite temperature
gauge theory. This corresponds to a backreacted non-extremal D3/D7 system.
At finite temperature, the fundamental matter undergoes a first order
phase transition. I will discuss this phase transition from the perspective of the supergravity dual.
|
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Tuesday, February 27, 2007
|
|
Chris Dawson
[Host: Hank Thacker]
|
|
3:30 PM, Room 204
|
|
Brookhaven National Lab |
| Physics Building |
|
“The Kaon B-Parameter from Lattice QCD” |
ABSTRACT:
| I will discuss the calculation of the Kaon B-parameter,
a measure of indirect CP-violation in the Standard Model,
using Lattice QCD. In particular, I will talk about the
use of the Domain Wall Fermion formulation of Lattice QCD,
a formulation which has continuum-like symmetry properties
at finite lattice spacing at the expense of the introduction
of an additional, fifth, dimension. |
|
Tuesday, February 20, 2007
|
|
Ross Young
[Host: Hank Thacker]
|
|
3:30 PM, Room 204
|
|
JLAB |
| Physics Building |
|
“Latest results on the low-energy search for new physics” |
ABSTRACT:
| The Standard Model has been enormously successful at predicting the
outcomes of experiments in nuclear and particle physics. The search for
new physical phenomena and a fundamental description of nature which goes
beyond the Standard Model is driven by two complementary experimental
strategies. The first is to build increasingly energetic colliders, such
as the Large Hadron Collider (LHC) at CERN, which aim to excite matter
into a new form. The second, more subtle approach, is to do precision
measurements at moderate energies, where an observed discrepancy with the
Standard Model will reveal the signature of these new forms of matter.
Here we demonstrate that the latest measurements of the electroweak force
severely constrain the possibility of physics beyond the Standard Model to
above the TeV energy scale. |
|
Wednesday, February 7, 2007
|
|
Swaolhin Tameja
[Host: Simonetta Liuti]
|
|
3:30 PM, Room 313
|
|
Ecole Polytechnique |
| Physics Building |
|
“New Developments In Generalized Parton Distributions” |
|
Tuesday, February 6, 2007
|
|
Wally Melnitchouk
[Host: Donal Day]
|
|
3:30 PM, Room 204
|
|
Jefferson Lab |
| Physics Building |
|
“Two-photon exchange in elastic electron-nucleon scattering” |
ABSTRACT:
| The ratio of the electric to magnetic proton form factors has
traditionally been determined using the Rosenbluth separation method,
in which the ratio is extracted from the angular dependence of the
cross section at fixed momentum transfer Q 2 . Measurements at JLab
using the alternative, polarization transfer technique found a
dramatically different behavior of the ratio compared with the
Rosenbluth results. I discuss the resolution of this discrepancy
by considering the effects of two-photon exchange in elastic e-p
scattering, taking particular account of the nucleon's finite size.
Contributions from excited nucleon intermediate states are also
considered, and estimates given of two-photon exchange corrections
to the form factors of the neutron and He-3.
|
|
Tuesday, December 5, 2006
|
|
Igor I. Strakovsky
[Host: Donal Day]
|
|
3:30 PM, Room 204
|
|
George Washington University |
| Physics Building |
|
“Partial-Wave Analysis and Spectroscopy in Pion-Nucleon Scattering up to W = 2.5 GeV” |
ABSTRACT:
| We present results from a comprehensive partial-wave analysis of pi+-p elastic scattering and charge-exchange data, covering the region from threshold to 2.6 GeV in the lab pion kinetic energy, employing a coupled-channel formalism to simultaneously fit pi-p-->eta n data to 0.8 GeV. Our main result, solution SP06, utilizes a complete set of forward and fixed-t dispersion relation constraints applied to the piN elastic amplitude. The results of these analyses are compared with previous solutions in terms of their resonance spectra and preferred values for couplings and low-energy parameters. Details are available at nucl-th/0605082
|
|
Tuesday, November 21, 2006
|
|
Thanksgiving Recess
[Host: N/A]
|
|
3:30 PM, Room 204
|
|
N/A |
| Physics Building |
|
“N/A” |
|
Tuesday, November 14, 2006
|
|
Kevin Giovanetti
[Host: Donal Day]
|
|
3:30 PM, Room 204
|
|
JMU |
| Physics Building |
|
“A precision measurement of the muon lifetime and the determination of the weak coupling constant |
ABSTRACT:
| For several years the MULAN collaboration has been pursuing the ambitious goal of a 1 ppm determination of the muon lifetime. This experiment has been motivated by recent theoretical improvements in extracting the Fermi coupling constant GF, from the measured muon lifetime, τμ, which have reached the 1 ppm level in the theoretical error. The coupling constant GF is an essential parameter of the Standard Model. Its uncertainty limits the precision for Standard Model predictions and interpretations. Progress and highlights of the experiment will be discussed. |
|
Tuesday, October 31, 2006
|
|
Larry Weinstein
[Host: Donal Day]
|
|
3:30 PM, Room 204
|
|
ODU |
| Physics Building |
|
“Positron-proton scattering and the proton charge distribution” |
ABSTRACT:
| This talk will describe how to make intense identical positron and electron beams at Jefferson Lab and use them to measure two-photon exchange contributions to elastic electron-proton scattering. It will cover the results of a recent test run in CLAS where we produced about 10 pA each of electrons and positrons.
The proton electric form factor describes the charge distribution of the proton. This has been measured extensively with electron scattering using Rosenbluth separations and polarization measurements. These measurements of the proton electric form factor disagree by a factor of three at Q 2 = 6 GeV 2 . Since alpha, the fine structure constant, is less than 1%, electron-proton scattering should be almost exclusively one-photon exchange. However, a two-photon exchange contribution of about 5% could explain the discrepancy between the measurements. We will determine the two-photon exchange contribution by measuring the ratio of the electron-proton and positron-proton elastic scattering cross sections to 1%. |
|
Tuesday, October 10, 2006
|
|
Brandon Craver
[Host: Donal Day]
|
|
3:30 PM, Room 204
|
|
UVA |
| Physics Building |
|
“A High Precision Measurement of G E n High Q 2 ” |
ABSTRACT:
| A precision measurement of the electric form factor of the neutron, G E n , has been carried out in Jefferson Lab's Hall A for Q 2 values of 1.2 to 3.5 (GeV/c) 2 using a highly polarized 3 He target and the quasi-elastic semi-exclusive 3 He(e,e'n) reaction. The experiment detected the ejected neutron with an array of scintillators and the scattered electron with the newly commissioned BigBite spectrometer. This new spectrometer has a large angular acceptance (80 msr), complementing the existing 6 msr high-resolution spectrometers, and enables a new generation of low-rate experiments with lower resolution requirements. A package of three multi-wire drift chambers was constructed in order to allow the spectrometer to operate under high rate conditions and achieve a spatial resolution of ~ 200 μm. The present status of the experiment will be presented as well as online results showing chamber performance at raw hit rates up to 20 MHz per plane. |
|
Tuesday, September 26, 2006
|
|
Inna Aznauyan
[Host: Donal Day]
|
|
3:30 PM, Room 204
|
|
Jefferson Lab |
| Physics Building |
|
“Q 2 Evolution of &gamma * N → N * Transition Amplitudes from Pion Electroproduction Data” |
ABSTRACT:
| I will make short introduction to clarify some notations used in N * physics and to present resonances which we have
investigated within N * program of Hall B (JLab).
Then I will discuss goals of N * program related to the
Q 2 evolution of &gamma * N &rarr N * amplitudes.
Here the focus will be on the investigation of the scale of
transition from nonperturbative to perturbative regime of QCD
and on the nature of the Roper resonance.
Further, I will discuss approaches used for the extraction
of resonance contributions to the pion electroproduction
and present the results obtained from JLab (mostly Hall B) data.
This will be followed by the discussion of the obtained results
and conclusion.
|
|
Tuesday, April 18, 2006
|
|
Chad Materniak
[Host: Donal Day]
|
|
3:30 PM, Room 204
|
|
UVA |
| Physics Building |
|
“Search for CP Violation in Hyperon Decays” |
|
Tuesday, April 11, 2006
|
|
Joe Pole
[Host: Donal Day]
|
|
3:30 PM, Room 204
|
|
UVA |
| Physics Building |
|
“Detector Physics in a Small Animal CT-SPECT Scanner” |
|
Tuesday, April 4, 2006
|
|
Dipangkar Dutta
[Host: Donal Day]
|
|
3:30 PM, Room 204
|
|
Duke University |
| Physics Building |
|
“Search for a Permanent Electric Dipole Moment (EDM) of the Neutron” |
ABSTRACT:
| The search for a non-zero neutron EDM is a direct search for time
reversal symmetry violation. Recently, a new experiment has been
proposed to search for the neutron electric dipole moment (nEDM) with
about two orders of magnitude improved sensitivity compared to the
current experimental limit. One of the critical new ideas, which
helps achieve the improved sensitivity, is the use of polarized
Helium-3 as a co-magnetometer. Polarized He-3 is a key new component
of this proposed experiment and thus maintaining its polarization
under the true experimental conditions is essential for the success
of the experiment. Following an overview of the past searches for the
neutron EDM, I will describe the new experiment and the effort
underway at Duke to study the relaxation of polarized He-3 under the
conditions of the new proposed experiment.
|
|
Tuesday, March 21, 2006
|
|
Oscar Rondon-Aramayo
[Host: Donal Day]
|
|
3:30 PM, Room 204
|
|
UVA |
| Physics Building |
|
“Nucleon Spin Physics Program in JLab's Hall C” |
ABSTRACT:
| The Hall C facility at Jefferson Lab is carrying out an extensive program of
studies on nucleon spin physics, taking advantage of the CEBAF polarized
electron beam and the versatile UVa polarized target. The program started in
2002 with a measurement of the longitudinal and transverse spin structure of the
nucleon resonances in experiment 01-006 (Resonances Spin Structure - RSS) on
proton and deuteron targets. This work is nearing publication of the final
results for the proton, which will be presented. Preliminary results for the
deuteron are available, too. The Spin Asymmetries on the Nucleon Experiment -
SANE (E-03-109) is in preparation to extend the measurements of RSS and other
experiments on the proton to higher momentum transfers. Going beyond inclusive
polarized scattering, the Semi-SANE experiment (E-04-113) will detect scattered
electrons and hadrons in coincidence, to determine the decomposition of the
nucleon spin into its quark flavor components. Both SANE and Semi-SANE are
scheduled to take data in 2008."
|
Joint Nuclear/High Energy Physics Seminar
|
Monday, March 13, 2006
|
|
Anna Stasto
[Host: Peter Arnold]
|
|
3:30 PM, Room 204
|
|
Brookhaven National Laboratory |
| Physics Building |
|
“High Energy Limit and Parton Saturation in QCD” |
ABSTRACT:
| High energy limit of QCD is the area of major theoretical interest. One of its prediction is the so called perturbative BFKL
Pomeron which manifests itself as a rapid growth of the gluon density
with increasing center-of-mass energy. Although the rise of this density is indeed observed in the deep inelastic experiments
at small values of Bjorken x, it is not compatible quantitatively with the prediction of the BFKL Pomeron.
This lead to the intensive investigation of the possible corrections
to the BFKL Pomeron such as higher order
and the high density corrections.
In this talk I will give an introduction to the high energy limit of QCD and discuss the idea of the parton saturation,
an effect that is expected to occur when the gluon density is very high.
I will describe the nonlinear evolution equation (Balitsky-Kovchegov equation) for the gluon density which takes into account high density corrections
and present its solution. The concept of the saturation scale and the geometrical scaling at small Bjorken x will be also introduced
as well as the interesting link between parton saturation in QCD and the statistical physics.
Finally, I discuss some phenomenological signatures of parton saturation and outline recent theoretical progress in
developing theory with so-called Pomeron loops, corrections which go beyond the Balitsky-Kovchegov equation.
|
|
Tuesday, March 7, 2006
|
|
****SPRING RECESS****
|
|
3:30 PM, Room 204
|
|
|
| Physics Building |
|
|
Join Nuclear/High Energy Seminar
|
Tuesday, February 28, 2006
|
|
Dan Pirjol
[Host: Peter Arnold]
|
|
3:30 PM, Room 204
|
|
MIT |
| Physics Building |
|
“Factorization in B decays from the Soft-Collinear Effective Theory” |
|
Tuesday, December 6, 2005
|
|
Richard Arndt
[Host: Donal Day]
|
|
3:30 PM, Room 204
|
|
Virginia Tech |
| Physics Building |
|
“Partial-Wave Analysis of Scattering Reactions” |
|
Tuesday, November 29, 2005
|
|
Pasi Huovinen
[Host: Donal Day]
|
|
3:30 PM, Room 204
|
|
UVa and University of Jyväskylä, Finland |
| Physics Building |
|
“Studying the QCD Equation of State with Hydrodynamics” |
ABSTRACT:
| The lattice QCD calculations predict a phase transition from hadronic
matter to matter where the basic degrees of freedom are partons
instead of
hadrons around 170 MeV temperature. It is hoped that this phase
transition
could be experimentally observed in the heavy ion collision
experiments at
BNL's RHIC collider. In this talk I will discuss how one can compare the
lattice QCD predictions to experimental results by using
hydrodynamics to
describe the expansion stage of the collision process. The data
favor a scenario with a phase transition, but surprisingly the order of
the phase transition seems to be different from the QCD prediction.
|
|
Tuesday, November 22, 2005
|
|
****THANKSGIVING BREAK****
|
|
3:30 PM, Room 204
|
|
|
| Physics Building |
|
|
This is a joint High Energy/Nuclear Seminar
|
Tuesday, November 8, 2005
|
|
John Ralston
[Host: Simonetta Liuti]
|
|
3:30 PM, Room 204
|
|
University of Kansas |
| Physics Building |
|
“Mixing Color and Spin” |
|
Tuesday, November 1, 2005
|
|
Stepan Stepanyan
[Host: Donal Day]
|
|
3:30 PM, Room 204
|
|
Jefferson Lab |
| Physics Building |
|
“Hunting the Pentaquark” |
ABSTRACT:
| In the past two years more than 13 experiments have reported observation of a narrow exotic S=+1 baryon state in the mass range from 1.525 to 1.55 GeV/c2. The minimal quark content of this state, now called the Θ+, is uudds. In contrast to almost fully exclusive experiments at low energies that have reported evidence for the Θ+, there have been a number of reports of non-observation of this state, mostly in high energy inclusive experiments. The main criticisms of the reported Θ+ signals are insufficient statistics, and variation in mass. Evidence for the doubly strange, Φ-- (known as Ξ--),and for the charmed, Θc, pentaquarks have been presented only in the single experiments.
The CLAS Collaboration at Jefferson Laboratory has published two papers on the experimental evidence for the Θ+ and Ξ--. These data now represent the world's largest data sets for photoproduction on hydrogen and deuterium. In this talk an overview of the experimental situation on the pentaquarks and the preliminary results of high statistics CLAS experiments will be presented. |
|
Tuesday, October 25, 2005
|
|
Elton Smith
[Host: Donal Day]
|
|
3:30 PM, Room 204
|
|
Jefferson Lab |
| Physics Building |
|
“Search for Gluonic Excitations at Jefferson Lab” |
ABSTRACT:
| One of the great mysteries of modern physics is the mechanism that
confines quarks into hadrons. Quarks are bound together due to the strong
interaction of gluons which themselves carry color charge. Although the
theory of quantum chromodynamics (QCD) describes the interaction, the
solutions can only be approximated at low energies. Nevertheless colored
gluons are expected to bind to each other and form flux tubes, which
lattice QCD predicts will be observable in the particle spectrum as new
excitations called hybrid mesons. We will describe the plans at Jefferson
Lab to double the energy of the machine to 12 GeV, which will allow access
these gluonic excitations experimentally, and describe the apparatus in
the new Hall D which will be used to search for them.
|
Joint Nuclear/High Energy Seminar
|
Thursday, October 20, 2005
|
|
Leonard Gamberg
[Host: Simonetta Liuti]
|
|
3:30 PM, Room 205
|
|
Penn State |
| Physics Building |
|
“Transversity Properties of Quarks and Hadrons Through Hard Scattering in QCD” |
|
Tuesday, October 4, 2005
|
|
David Armstrong
[Host: Donal Day]
|
|
3:30 PM, Room 204
|
|
College of William and Mary |
| Physics Building |
|
“Strangeness in the Proportion: Parity-Violating Electron Scattering and the Structure of the Nucleon” |
ABSTRACT:
| The fleeting existence of quark-antiquark pairs within the proton
(or neutron) is a well-established consequence of quantum
chromodyamics. It is, however, still a largely open question as to
whether this sea of quark-antiquark pairs, which contains
contributions from all the quark flavors (up, down, strange, etc.), has
any effect on the properties of the nucleon. In particular,
the contribution of the sea to the magnetic moment and the charge
distribution of the proton has been a topic of considerable interest.
A series of experiments, using parity-violating electron scattering
to probe of the sea, have been conducted at various labs in recent
years. The results of these experiments, in particular the
G0 and HAPPEX experiments at Jefferson Lab, will be reviewed, and
possible interpretations of the results will be presented. |
|
Tuesday, September 27, 2005
|
|
Andrei Afanasev
[Host: Donal Day]
|
|
3:30 PM, Room 204
|
|
Jefferson Lab |
| Physics Building |
|
“Higher-Order QED for Precision Studies of Electron Scattering” |
ABSTRACT:
| High precision of electron scattering experiments on nucleons and
nuclei requires precise methods to include electromagnetic radiative
corrections. Using an example of elastic electron-nucleon scattering,
I will describe an important role of higher-order Quantum
Electrodynamic techniques for the studies of hadronic structure with
electron beams. |
|
Tuesday, September 20, 2005
|
|
Stephen Bueltmann
[Host: Donal Day]
|
|
3:30 PM, Room 204
|
|
Old Dominion University |
| Physics Building |
|
“The BoNuS Experiment at Jefferson Lab” |
ABSTRACT:
| Unlike the structure of the proton, our understanding of the structure of the
neutron to date is limited by the unavailability of free neutrons. The BoNuS collaboration at Jefferson Lab is preparing an experiment
to augement the CLAS detector in Hall B with a recoil detector to measure the momentum of
recoiling protons in electron scattering on a deuterium target. The detection of very low momentum spectator protons at very backward
scattering angles selects electron scattering events on almost free neutrons inside the
deuteron. The newly developed recoil detector and gas target system has to be built out of lightweight materials to not absorb the very low momentum spectator protons before being detected. The experiment is scheduled to start data
taking in the middle of Octber 2005 and results from an engineering run in June 2005 are presented.
|
|
Tuesday, April 26, 2005
|
|
Jaideep Singh
[Host: Gordon Cates]
|
|
3:30 PM, Room 204
|
|
UVA |
| Physics Building |
|
“The GDH Sum Rule, the Spin Structure of Helium-3 and the Neutron using Nearly Real Photons” |
|
Tuesday, April 19, 2005
|
|
Josh Pierce
[Host: Don Crabb]
|
|
3:30 PM, Room 204
|
|
UVA |
| Physics Building |
|
“Measurements of the Extended GDH Sum Rule at J-Lab” |
Hoxton Lecture
|
Tuesday, April 19, 2005
|
|
Saul Perlmutter
[Host: Brad Cox]
|
|
7:30 PM, Room 402
|
|
University of California - Berkeley |
| Chemistry Building Auditorium |
|
“Supernovae, Dark Energy, and the Accelerating Universe” |
ABSTRACT:
| This constant acted as a sort of anti-gravity to counteract the force of gravity that would otherwise be pulling the masses of the universe together. When astronomers such as Hubble and others subsequently observed the red shifts of far distant stars and galaxies, they discovered that the universe is not static but, indeed, is expanding. Therefore, it no longer seemed necessary to have a counter balance to gravity. It is said that Einstein, when he heard of the expansion of the universe, characterized his use of a cosmological constant his greatest mistake. Indeed, for the better part of 100 years the standard view of the universe was that its expansion rate was gradually slowing down under the influence of the gravity of its components. The question of the future of the universe was posed in terms of, depending on the total mass of the universe, whether the universe would come to a stop and fall back in on itself, come to a halt at infinite time, or continue to expand forever.
Professor Perlmutter and his colleagues, using Supernovas Type Ia as “standard candles” because of their great brightness, have measured the expansion rate of the universe at much large distances than previously possible. In doing so, they have made the remarkable discovery that the expansion of the universe is actually accelerating. There appears to be a previously undetected force of nature that acts like antigravity, dominating the gravitational force and causing the universe to expand faster and faster with time. So the better part of a century after the cosmological constant was abandoned, it seems that it must be re-employed to describe this new phenomenon which has been labeled dark energy. Perhaps Einstein was right after all!
|
|
Tuesday, April 12, 2005
|
|
Swadhin Taneja
[Host: Gordon Cates]
|
|
3:30 PM, Room 204
|
|
UVA |
| Physics Building |
|
“Study of Bound Nucleons Using Generalized Parton Distributions” |
|
Tuesday, April 5, 2005
|
|
Nadia Fomin
|
|
3:30 PM, Room 204
|
|
UVA |
| Physics Building |
|
“Inclusive Scattering From Nuclei at x>1 and High Q^2 with a 5.75 GeV Beam” |
|
Tuesday, March 29, 2005
|
|
Ryan Snyder
[Host: Gordon Cates]
|
|
3:30 PM, Room 204
|
|
UVA |
| Physics Building |
|
“HAPPEX: Using Parity Violation to Probe Nucleon Strangeness” |
|
Tuesday, November 30, 2004
|
|
Gail Dodge
[Host: Simonetta Liuti]
|
|
3:30 PM, Room 204
|
|
Old Dominion University |
| Physics Building |
|
“Spin Structure Functions: A Window into the Structure of Hadrons” |
|
Tuesday, November 9, 2004
|
|
Kebin Wang
[Host: Blaine Norum]
|
|
3:30 PM, Room 204
|
|
UVA |
|
|
“Proposed Measurement of Pion Polarizabilities in JLab-Hall B” |
|
Wednesday, June 23, 2004
|
|
Shigeyuki Tajima
[Host: Donal Day]
|
|
3:30 PM, Room 204
|
|
Duke University |
| Physics Building |
|
“Measurements of the Electric Form Factor of the Neutron” |
ABSTRACT:
| Precise measurements of the electric form factor of the neutron, Gen, over a wide range of the square of the four-momentum transfer, Q^2, are important for understanding nucleon and nuclear
electromagnetic structure. The Jefferson Laboratory E93-038 collaboration recently reported the first measurements of Gen using
polarization techniques at Q^2 > 1 (GeV/c)^2. The collaboration measured the ratio of the electric form factor to magnetic form factors of the neutron, g = Gen/Gmn, at three Q^2 values (0.45, 1.13 and 1.45 (GeV/c)^2) using the quasi-elastic 2H(\vec e,e'\vec n)1H reaction. The value for g was determined from the measured ratio of
the sideways and longitudinal components of the neutron polarization vector. A polarimeter based on np scattering was used to analyze the
polarization of the recoil neutrons. In this talk, the data analyses and our results for g and Gen at Q^2=0.45 and 1.13 (GeV/c)^2 will be
given.
|
|
Tuesday, April 27, 2004
|
|
Karapet Oganessyan
[Host: Simonetta Liuti]
|
|
3:30 PM, Room 204
|
|
DESY |
| Physics Building |
|
“Novel Transversity Properties in Semi-Inclusive Deep Inelastic Scattering” |
|
Tuesday, April 20, 2004
|
|
Gerald Miller
[Host: Simonetta Liuti]
|
|
2:00 PM, Room 313
|
|
University of Washington |
| Physics Building |
|
“The Proton Form Factor and the Shape of the Proton” |
|
Tuesday, April 20, 2004
|
|
Scott Rohrbaugh ( Biological Physics)
[Host: Gordon Cates]
|
|
3:30 PM, Room 204
|
|
UVA |
| Physics Building |
|
“Spin relazation of 129Xe from paramagnetic impurities” |
|
Tuesday, March 30, 2004
|
|
Dave Gaskell
[Host: Donal Day]
|
|
3:30 PM, Room 204
|
|
Jefferson Laboratory |
| Physics Building |
|
“Transverse Target Asymmetry in Exclusive Pi+ Production” |
|
Tuesday, March 2, 2004
|
|
Simonetta Liuti
[Host: Gordan Cates]
|
|
3:30 PM, Room 204
|
|
UVA |
| Physics Building |
|
“Subatomic Journal Club” |
|
Tuesday, February 24, 2004
|
|
Bodo Reitz
[Host: Nilanga Liyanage]
|
|
3:30 PM, Room 204
|
|
Jefferson Lab |
| Physics Building |
|
“Studies of Short-Range Correlations and Reaction Dynamic Effects in the 4He(e,e'p) Reaction” |
ABSTRACT:
| Studying few-body nuclear targets in the (e,e'p) reaction
is a powerful method to investigate specific aspects of the nucleus.
The 4He nucleus is an especially interesting target since it has
many of the ingredients of a complex, heavy nucleus, while as an A=4
system, microscopic calculations are still feasible.
Making use of the high luminosity electron beam at Jefferson Lab
together with the high resolution spectrometers in Hall A,
Jefferson Lab Hall A experiment E97-111 has measured the
4He(e,e'p)3He cross section at recoil momenta up to~500 MeV/c in various
kinematics. In plane-wave impulse approximation, many calculations
predict a sharp minimum in the cross section for recoil
momenta around 450~MeV/c and show that its location
is sensitive to the short-range part of the internucleon potential.
However, reaction dynamic effects such as final-state
interactions and meson-exchange currents can obscure such a minimum.
Measuring this cross section at various kinematical settings over the
same recoil-momentum range gives the possibility to study these reaction
dynamics effects. Preliminary results of this experiment will be
presented, and will be compared to recent theoretical predictions. |
|
Tuesday, February 3, 2004
|
|
Sergey Alekhin
[Host: Simonetta Liuti]
|
|
3:30 PM, Room 204
|
|
Institute for HEP, Serpukhov |
| Physics Building |
|
“The latest global analyses of parton distribution functions” |
Nuclear Seminar - PLEASE NOTE SPECIAL ROOM
|
Tuesday, December 9, 2003
|
|
Karl Slifer
[Host: Donal Day]
|
|
3:30 PM, Room 313
|
|
Temple University |
| Physics Building |
|
“Neutron Spin Structure at Low Q2 Using a Polarized 3He Target” |
ABSTRACT:
| We have measured the spin dependent longitudinal and transverse 3He(e,e,) cross sections for 0.12<0.9 GeV2 covering the quasielastic and resonance regions and extending into the deep inelastic scattering region. Jefferson Lab's longitudinally polarized electron beam of incident energy 0.8 GeV to 5.0 GeV was scattered from a high pressure polarized 3He target in experimental Hall A. Longitudinal and transverse target polarization was maintained, allowing extraction of both spin structure functions g1 and g2. This measurement allows evaluation of the structure function higher moments, including the extended GDH sum, for both 3He and the neutron. These results when compared to theoretical models provide insight into the transition from the perturbative to the non-perturbative regine of QCD. |
|
Tuesday, November 11, 2003
|
|
Pibero Djawotho
|
|
3:30 PM, Room 204
|
|
College of William & Mary |
| Physics Building |
|
“Measurement of the Neutron (3He) Spin Structure Functions at Low Q2; a Connection between the Bjorken and Gerasimov-Drell-Hearn Sum Rule” |
ABSTRACT:
| This talk presents results of experiment E94-010 performed at JLAB (simply known as JLab) in Hall A. The experiment aimed to measure the low Q2 evolution of the Gerasimov-Drell-Hearn(GDH) integral from Q2 = 0.1 to 0.9 GeV2. The GDH sum rule at the real photon point provides an important test of Quantum Chromodynamics (QCD) radiative rections. The low Q2 evolutions of the GDH integral contests various resonance models. Chiral Perturbation Theory and lattice QCD calculations, but more importantly, it helps us understand the transition between partonic and hadronic degrees of freedom. At high Q2, beyond 1 GeV2, the difference of the GDH integrals for the proton and the neutron is related to the Bjorken sum rule, another fundamental test of QCD radiative corrections. In addition, results of the measurements for the spin structure functions g1 and g2 cross sections, and asymmetries are presented. E94-010 was the first experiment of its kind at JLAB. It used a high-pressure, polarized 3He target with a gas pressure of 10 atm and average target polarization of 38%. For the first time, the polarized electron source delivered an average beam plarization of 70% with a beam current of 15 µa; The limit on the beam current was only imposed by the target. The experiment required six different beam energies from 0.86 to 5.1 GeV. This was the first time the accelerator ever reached 5.1 GeV. Both High-Resolution Spectrometers of Hall A, used in singles mode, were positioned at 15.5 degree; each. |
|
Tuesday, September 30, 2003
|
|
Paul Kingsberry
[Host: Donal Day]
|
|
3:30 PM, Room 204
|
|
Department of Physics and Astronomy, University of New Mexico |
| Physics Building |
|
“P+PBAR -> LAMBDA+LAMBDABAR WITH A POLARIZED TARGET” |
ABSTRACT:
| The reaction p+pbar -> lambda+lambdabar was examined by CERN
experiment PS185/3 at the Low-Energy Antiproton Ring (LEAR) with beam
momenta of 1.525 GeV/c and 1.640 GeV/c. The proton target was
transversely polarized to enable measurements of the depolarization
and spin transfer, which quantify the transfer of the transverse spin
of the target proton to that of the outgoing lambda and lambdabar,
respectively. Theoretical calculations of Dnn, the component of the
depolarization normal to the production plane, differ greatly
according to whether quark-gluon or meson-exchange models are utilized.
Final results for the measured depolarization Dnn and spin transfer
Knn will be presented for both beam momenta. These results appear to
be inconsistent with the specific angular distributions predicted
under the assumptions of both production scenarios. |
|
Tuesday, May 20, 2003
|
|
Kebin Wang
[Host: Blaine Norum]
|
|
3:30 PM, Room 313
|
|
UVA |
| Physics Building |
|
“Hadronization in Nucleus by Deep Inelastic Scattering” |
|
Tuesday, May 13, 2003
|
|
Alexander Stolin
[Host: Mark Williams]
|
|
3:30 PM, Room 313
|
|
UVA |
| Physics Building |
|
“Development of CT-SPECT scanner for small animal imaging” |
|
Tuesday, May 6, 2003
|
|
Brad Sawatzky
[Host: Norum]
|
|
3:30 PM, Room 313
|
|
UVA |
| Physics Building |
|
“A Measurement of the Neutron Asymmetry in Near-Threshold DeuteriumPhoto-Disintegration ” |
|
Tuesday, April 29, 2003
|
|
Brent A. VanDevender
[Host: Dinko Pocanic]
|
|
3:30 PM, Room 204
|
|
UVA |
| Physics Building |
|
“Achieving Proposed Accuracy in the PIBETA Experiment -- It's About Time!” |
ABSTRACT:
| In order for PIBETA to attain its proposed accuracy it is imperative that
all electronic artifacts be removed from the timing scheme in offline
analysis. Some progress has been made but it is evident that attepts to
extend these improvements with traditional ADC/TDC methods will be
impossible. The efforts can be salvaged however by studying digitized
waveforms and developing new timing algorithms which exploit the raw
signals.
|
|
Tuesday, April 22, 2003
|
|
Ying Wang
[Host: Dinko Pocanic]
|
|
3:30 PM, Room 204
|
|
UVA |
| Physics Building |
|
“PIBETA experiment: PIBETA Detector Waveform Digitizing System” |
|
Tuesday, April 15, 2003
|
|
Maxim Bychkov
[Host: Dinko Pocanic]
|
|
3:30 PM, Room 204
|
|
UVA |
| Physics Building |
|
“PIBETA experiment: overview and preliminary results” |
|
Tuesday, March 11, 2003
|
|
Prof. Stanly J. Brodsky
[Host: Xiaotong Song]
|
|
3:30 PM, Room 204
|
|
SLAC |
| Physics Building |
|
“The Unexpected Effects of Final-State Interactions in QCD” |
ABSTRACT:
| It is usually assumed that the structure functions measured in deep
inelastic lepton-proton scattering are the probability distributions
for finding quarks and gluons in the target nucleon. In fact, gluon
exchange between the fast, outgoing partons and the target spectators,
which is usually assumed to be an irrelevant gauge artifact, affects
the leading-twist structure functions in a profound way, leading to
diffractive leptoproduction processes, shadowing of nuclear structure
functions, and target spin asymmetries. In particular, final-state
interactions from gluon exchange leads to single-spin asymmetries in
semi-inclusive deep inelastic lepton-proton scattering which are not
power-law suppressed at large photon virtuality Q^2 at fixed x_{bj}. |
|
Tuesday, February 25, 2003
|
|
Dr. Senho Choi
[Host: Nilanga Liyanage]
|
|
3:30 PM, Room 204
|
|
Temple University |
| Physics Building |
|
“Study of the Porized Structure Functions of the Neutron at Low Q2 with Polarized 3He ” |
|
Tuesday, February 18, 2003
|
|
Prof. Murray Peshkin
[Host: Xiaotong]
|
|
3:30 PM, Room 204
|
|
Argonne National Laboratory |
| Physics Building |
|
“Spin and Statistics in Nonrelativistic Quantum Mechanics''” |
ABSTRACT:
| The connection between spin and statistics is usually proved by using
the full machinery of relativistic quantum field theory, providing
little insight into what physics actually underlies it or whether there
can be exceptional cases. I will show, using elementary methods of
ordinary nonrelativistic quantum mechanics that identical zero-spin
particles must obey symmetric statistics. The key assumption is that no
dynamical variable in the theory distinguishes among identical spin-zero
particles. Whether this approach can be extended to identical particles
with nonvanishing spin is currently uncertain. |
|
Tuesday, January 14, 2003
|
|
Alexandra Fantoni
[Host: Simonetti Liuti]
|
|
3:30 PM, Room 204
|
|
INFN, Laboratorio Nazionale di Frascati |
| Physics Building |
|
“Quark-Hadron Duality Studies in Polarised Structure Functions” |
SPECIAL NUCLEAR SEMINAR
|
Monday, November 25, 2002
|
|
Charles Earl Hyde-Wright
[Host: Donal Day]
|
|
3:30 PM, Room 204
|
|
Old Dominion University |
| Physics Building |
|
“'Peering deeply into the proton: Deeply Virtual Compton Scattering and Generalized Parton Distributions” |
Special Nuclear Seminar
|
Tuesday, October 22, 2002
|
|
Mike Clark
[Host: George Gillies]
|
|
3:30 PM, Room 204
|
|
NRPB - England |
| Physics Building |
|
“Radiation and Gravity” |
ABSTRACT:
| The standard phenomenological model for the interaction for ionising radiation with matter, originally formulated by Bethe and widely used to calculate the transfer of energy, can also be used to model the quantum exchange processes that mediate forces. Such models are shown to be compatible with Newtonian gravitation and with the principle of weak equivalence. The gravitational constant G (kg –1 m3 s –2) can be related to Planck’s constant h, the speed of light c, the atomic mass unit u, and a dimensionless coupling constant ag. The applications and implications of the derived formulation will be examined. This formulation for G gives a new interpretation of Planck quantities, and a prediction emerges for experimental values of G to increase with increasing temperature of the attracting mass. Finally, gravitational shielding is predicted to occur but at vanishingly small proportions both in the laboratory and in the cosmos.
* M J Clark is at the National Radiological Protection Board, Chilton, Didcot, OX11 0RQ, UK (e-mail mike.clark@nrpb.org.uk).
|
|
Tuesday, April 30, 2002
|
|
Vina Punjabi
[Host: S. Liuti]
|
|
3:30 PM, Room 204
|
|
Norfolk State University |
| Physics Building |
|
“Measurement of the Ratio G_Ep/G_Mp at large Q^2 at Jefferson Lab” |
|
Tuesday, February 26, 2002
|
|
Markus Diehl
[Host: G. Cates]
|
|
3:30 PM, Room 204
|
|
DESY |
| Physics Building |
|
“Generalized parton distributions and their ramifications” |
|
Tuesday, January 15, 2002
|
|
Stefen Bass
[Host: S. Liuti]
|
|
3:30 PM, Room 204
|
|
Department of Physics, Duke University & RIKEN-BNL Research Center Fellow |
| Physics Building |
|
“ Quark-Gluon-Plasma Theory: Overview of status and perspectives” |
ABSTRACT:
| It is believed that shortly after the creation of the universe in
the Big Bang all matter was in a state called the Quark Gluon Plasma
(QGP).
Due to the rapid expansion of the Universe, this plasma went through
a phase transition to form hadrons and nuclear matter as we know it today.
The investigation of QGP properties will yield important novel insights
into the development of the early universe and the behavior of QCD
under extreme conditions.
It is sought to recreate this highly excited state of primordial matter
under controlled laboratory conditions using relativistic heavy ion
collisions, e.g. at the Super-Proton-Synchrotron (SPS) at CERN and at
the Relativistic Heavy-Ion Collider (RHIC) at
Brookhaven National Laboratory. SPS and first RHIC data
have yielded many interesting and
sometimes surprising results which have not yet been fully
evaluated or understood by theory.
I will review the current status of QGP theory - main emphasis will
be put on what we have learned at the SPS and at RHIC and what the most
pressing challenges are for the near future. |
|
Tuesday, December 4, 2001
|
|
Sergey Kulagin
[Host: S. Liuti]
|
|
3:30 PM, Room 204
|
|
Institute for Nuclear REsearch, Moscow |
| Physics Building |
|
“Nuclear Physics of Parton Distributions” |
|
Tuesday, November 13, 2001
|
|
X. Ji
[Host: Xiatong Song]
|
|
3:30 PM, Room 204
|
|
University of Maryland |
| Physics Building |
|
“GDH Sum Rule” |
|
Tuesday, October 23, 2001
|
|
Renee Fatemi
[Host: H. Weber]
|
|
3:30 PM, Room 204
|
|
UVA |
| Physics Building |
|
“The Spin Structure of the Proton in the Resonance Region” |
ABSTRACT:
| Inclusive double spin asymmetries p(e,e') measured in Hall-B at Jefferson Lab show that the resonance region contributes significantly to the low Q2 (0.15-1.2 GeV2) evolution of the structure function gp1(x,Q2) and its first moment. These results have important implications for the limits of current pQCD predictions as well as for the expected low Q2 convergence to the Gerasimov-Drell-Hearn Sum Rule. |
|
Tuesday, October 9, 2001
|
|
Rocco Schiavilla
[Host: H. J. Weber]
|
|
3:30 PM, Room 204
|
|
JLAB |
| Physics Building |
|
“A Random Walk in the Physics of Light Nuclei” |
ABSTRACT:
| In this talk I will discuss our current understanding, based on realistic nuclear Hamiltonians and currents, of a number of disparate issues generally relating to the structure and dynamics of light nuclei. These include: energy spectra of light nuclei with A up to 10, the determination of GEn from d(e,e')d data, longitudinal and transverse strength in the quasi-elastic (e,e') response of nuclei, the determination of parity-violating components of the NN interaction from pp elastic scattering, and finally (time permitting) an update on hep neutrinos from SuperK. |
Please Note Special Date and Time
|
Thursday, September 27, 2001
|
|
Patrick Hautle
[Host: Donald Crabb]
|
|
3:30 PM, Room 204
|
|
PSI |
| Physics Building |
|
“Polarized Scintillating Targets for Spin Physics” |
|
Tuesday, September 25, 2001
|
|
B. Borosoy
[Host: Blaine Norum]
|
|
3:30 PM, Room 204
|
|
Technical University |
| Physics Building |
|
“Chiral Dynamics of the eta-prime meson” |
ABSTRACT:
| The lowest-lying nonet of pseudoscalar mesons consists of the Goldstone boson octet of pions, kaons and the eta, which become massless in the chiral limit of zero quark masses, and the corresponding singlet state, the eta-prime, which, on the other hand, remains a massive state in the chiral limit due to the axial U(1) anomaly.
In order to describe the interactions of the eta-prime with the Goldstone boson octet at low energies, the conventional chiral effective Lagrangian is extended to include the eta-prime. The results presented in this talk include (eta)-(eta-prime) mixing and the dominant decay mode of the eta-prime into (eta bion pion). Furthermore, we conbine the chiral Lagrangian approach with a coupled channel analysis, in order to investigate eta-prime electroproduction off the nucleons.
The investigation of the eta-prime may offer new insights into the role of the axial U(1) anomaly in chiral dynamics. |
|
Tuesday, September 18, 2001
|
|
Scott Wilburn
[Host: Dinko Pocanic]
|
|
3:30 PM, Room 204
|
|
LANL |
| Physics Building |
|
“Measurement of Neutron Beta Decay Parameters with a Polarized Pulsed Cold Neutron Beam” |
Special Research Talk
|
Tuesday, May 1, 2001
|
|
Yongsoo Yoon
[Host: Thomas Gallagher]
|
|
4:00 PM, Room 204
|
|
Univ. of California |
| Physics Building |
|
“Probing Quantum Phase Transitions with NanoCalorimeter” |
|
Tuesday, April 17, 2001
|
|
Larry Weinstein
[Host: Ralph Minehart]
|
|
3:30 PM, Room 204
|
|
ODU |
| Physics Building |
|
“N N Corelations in 3He(e,e'pp) n' ” |
|
Tuesday, April 10, 2001
|
|
Ioana Niculescu
[Host: D. Pocanic]
|
|
3:30 PM, Room 204
|
|
Jefferson Lab |
| Physics Building |
|
“Exploring Quark-Hadron Duality at Medium Energies” |
ABSTRACT:
| Quark-hadron duality reflects the relationship between the quark and
hadron descriptions of hadronic processes and is related to the nature
of the transition from non-perturbative to perturbative QCD. The
phenomenon of duality can be studied in a variety of processes, such
as e+e- annihilation, deep inelastic scattering, heavy quark
decays, etc. Recent data on inclusive electron-proton and
electron-deuteron inelastic scattering obtained at Jefferson Lab were
utilized for precision tests of quark-hadron duality. These results
will be presented, together with future plans of testing/expanding the
concept of quark-hadron duality at Jefferson Lab. |
|
Tuesday, April 3, 2001
|
|
Kent Pashke
[Host: Ralph Minehart]
|
|
3:30 PM, Room 204
|
|
Carnegie Mellon |
| Physics Building |
|
“Probing the Spin Structure of Strangeness Production: ” |
Special Colloquium
|
Tuesday, March 20, 2001
|
|
Ashot Gasparian
[Host: Gordon Cates]
|
|
3:30 PM, Room 204
|
|
Jefferson Lab |
| Physics Building |
|
“The Chiral Anomaly and Neutral Pion Lifetime” |
ABSTRACT:
| The system of the three light neutral mesons, pi-zero, eta eta-prime, contains fundamental information
about chiral symmetry breaking in low energy QCD. In particular, SU(3)and isospin breaking by the light quark masses lead to important mixing effects among the mesons. Because
of the small mass of the pion, the prediction of the chiral anomaly for the pi-zero To gamma - gamma decay width is more accurate and exact in the limit of massless quarks. In this limit the predicted
decay width depends only on two fundamental constants: the number of colors in QCD,and
the pion decay constant.The “PrimEx ” collaboration at Jefferson Lab will perform a high
precision measurement of the neutral pion lifetime using the small angle coherent
photoproduction of pi-zero's in the Coulomb field of a nucleus,i.e., the Primakoff effect. After giving a
general overview of chiral symmetry breaking and the appearance of the chiral anomaly at
low energies,this talk will present previous measurements and focus on the current experiment at JLab. The experimental program for the more massive eta and eta-prime mesons with the
12 GeV JLab energy upgrade will also be discussed. |
|
Tuesday, February 13, 2001
|
|
Yelena Prok
[Host: Dinko Pocanic]
|
|
3:30 PM, Room 204
|
|
University of Virginia - Physics Dept. |
| Physics Building |
|
“The measurement of the spin structure function g1 in the resonance region” |
|
Tuesday, December 12, 2000
|
|
Raju Venugopalan (POSTPONED)
[Host: Simonetta Liuti]
|
|
3:30 PM, Room 204
|
|
BNL |
| Physics Building |
|
“TBA” |
|
Tuesday, December 5, 2000
|
|
Haiyan Gao
[Host: Simonetta Liuti]
|
|
3:30 PM, Room 204
|
|
MIT |
| Physics Building |
|
“JLab experiment E95-001: quasielastic scattering of polarized electrons from Polarized 3He nuclei” |
|
Tuesday, November 21, 2000
|
|
Qwar Benhar
[Host: S. Liuti]
|
|
3:30 PM, Room 204
|
|
INFN, Rome |
| Physics Building |
|
“The Imprint Of The Equation of State on the Acial W- Modes of Oscillating Neutron Stars” |
|
Tuesday, October 24, 2000
|
|
Gordon Cates (POSTPONED)
|
|
3:30 PM, Room 204
|
|
UVA- Physics Department |
| Physics Building |
|
“TBA” |
|
Tuesday, October 17, 2000
|
|
Mark Strikman
[Host: Donal Day]
|
|
3:30 PM, Room 204
|
|
Penn State University |
| Physics Building |
|
“Perspectives of using high-energy electron scattering for probing microscopic nuclear structure” |
|
Tuesday, October 10, 2000
|
|
Emil Frlez
[Host: Dinko Pocanic]
|
|
3:30 PM, Room 204
|
|
University of Virginia |
| Physics Building |
|
“Is There A Tensor Admixture To V-A Interaction In The Radiative Pion Decay?” |
ABSTRACT:
| The PIBETA experiment at PSI has been taking data for over a year. Acquired statistics of rare pion and muon decays exceeds now the previous world total by up to an order of magnitude. In this talk I will examine the pi+ --> e+ gamma events collected so far, especially in the part of the phase space sensitive to deviations from the canonical V-A interaction. As the PIBETA detector is running with 12 simultaneous physics triggers, the cross-normalization of different decay channels enables us to extract the absolute pi+ --> e+ nu gamma branching ratio in a simple way and compare it with a straightforward theoretical calculation. |
Special Instrumentation Seminar
|
Tuesday, October 3, 2000
|
|
H. P. Wirtz
[Host: D. Pocanic]
|
|
3:30 PM, Room 204
|
|
Paul Scherrer Institute |
| Physics Building |
|
“Waveform Digitization with the Domino Sampling Chip in the PIBETA Experiment” |
*Nuclear Seminar- Please note change in room location
|
Monday, September 25, 2000
|
|
I. Sick
[Host: Donal Day]
|
|
3:30 PM, Room 313
|
|
Univ. Basel |
| Physics Building |
|
“Many Body Theory Interpretation of Deep Inelastic Scattering” |
National Physics Day Show
|
Thursday, April 27, 2000
|
|
Stephen Thornton/Robert Watkins
[Host: Physics Department]
|
|
6:30 PM, Room 203
|
|
University of Virginia |
| Physics Building |
|
“The Sixth Annual National Physics Day Show” |
SPECIAL CHEMICAL PHYSICS SEMINAR
|
Tuesday, April 18, 2000
|
|
Gwyn Williams
[Host: Robert Jones]
|
|
3:30 PM, Room 204
|
|
JLAB |
| Physics Building |
|
“Surface Dynamics Using Synchrotron Radiation” |
|
Tuesday, April 11, 2000
|
|
C V K Baba
[Host: P. K. Kabir]
|
|
3:30 PM, Room 204
|
|
Tata Institute of Fundamental Research, Bombay |
| Physics Building |
|
“A Search for Color van der Waals Interaction” |
|
Tuesday, April 4, 2000
|
|
Xiatong Song
[Host: Hans J. Weber]
|
|
3:30 PM, Room 204
|
|
University of Virginia |
| Physics Building |
|
“Spin Structure Function g2” |
Joint Nuclear/High Energy
|
Tuesday, March 21, 2000
|
|
Sabine Jeschonnek
[Host: Simonetta Liuti]
|
|
3:30 PM, Room 204
|
|
Jefferson Lab |
| Physics Building |
|
“Search for the Origin of Duality” |
|
Tuesday, March 14, 2000
|
|
Frank Wesselmann
[Host: Donal Day]
|
|
3:30 PM, Room 204
|
|
Old Dominion University |
| Physics Building |
|
“Precision Measurement of the Spin Structure of the Proton and the Deuteron” |
ABSTRACT:
| Over the past decade, many experiments have measured the nucleon spin
structure functions using polarized deep inelastic scattering, both in the
US and in Europe.
After a brief survey of these efforts, the results from SLAC experiments
E155 and E155x will be presented. This pair of experiments has measured g1
and g2 of the proton and the deuteron with high precision and over a large
kinematic range, providing the best measurements available. In the
discussion of these measurements, special attention will be given to the
radiative corrections, which have a significant impact on the measured
results and also on statistical and on systematic errors.
|
|
Tuesday, March 7, 2000
|
|
Larry Cardman
[Host: Blaine Norum]
|
|
3:30 PM, Room 204
|
|
Jefferson Laboratory, Newport News, VA |
| Physics Building |
|
“CEBAF @ Jefferson Lab: A New Microscope for Nuclear Physics” |
|
Tuesday, February 29, 2000
|
|
Dustin McNulty
[Host: Don Crabb]
|
|
3:30 PM, Room 204
|
|
University of Virginia |
| Physics Building |
|
“A Precise Measurement of the g2 Structure Function of the Proton and Deuteron” |
Special Nuclear Seminar
|
Thursday, January 27, 2000
|
|
Helmut Haberzettl
[Host: Hans Weber]
|
|
3:00 PM, Room 313
|
|
George Washington University |
| Physics Building |
|
“Theoretical issues of interacting mesons, baryons and photons” |
*Special Science Education Seminar
|
Tuesday, December 14, 1999
|
|
Dr. William Junkin
[Host: Stephen Thornton]
|
|
3:30 PM, Room 203
|
|
Erskine College |
| Physics Building |
|
“Web-based Software to Enhance Instructor-Student Interaction” |
ABSTRACT:
| Web-based (HTML) software will be introduced which enhances student learning by
increasing student involvement and instructor-student interaction. Most of these
interactive or polling software and templates, some of which I have developed,
are free. They are used in "Peer Instruction" developed by Eric Mazur (Harvard
University) and "JiTT" (Just-in-Time Teaching) developed by Novak and Garvin
(IUPUI), Patterson (Air Force Academy), and Christian (Davidson). These recent
pedagogies have been used effectively in physics and other disciplines at the
high school and undergraduate level. Preliminary results of using some of this
software with traditional introductory physics labs are especially promising.
This session will demonstrate these materials, make them available to those that
are interested, explain how to make them work on your platform or network,
explain how to combine them with other web-based materials, and mention results
from using them. The session is designed for anyone, novice web-surfer to
experienced web-master.
|
|
Tuesday, October 26, 1999
|
|
Wally Melintchouk
[Host: S. Luiti]
|
|
3:30 PM, Room 204
|
|
University of Aolelaisle/Jefferson Lab |
| Physics Building |
|
“Mirror nuclei, the neutron and quark-hadron duality” |
|
Tuesday, October 19, 1999
|
|
Xiaotong Song
|
|
3:30 PM, Room 204
|
|
University of Virginia - Physics Dept |
| Physics Building |
|
“Substructure of the Nucleon” |
|
Tuesday, October 5, 1999
|
|
Norm Kolb
[Host: Blaine Norum]
|
|
3:30 PM, Room 204
|
|
University of Saskachewan |
| Physics Building |
|
“Probing Chiral Symmetry with Photonuclear Reactions” |
ABSTRACT:
| Chiral Perturbation Theory (ChPT) is an effective field theory in which the spontaneous breaking of the Quantum Chromodynamic (QCD) chiral symmetry is exploited to make predictions for many low-energy processes. Nuclear Compton scattering and near-threshold pion photoproduction are two of the phenomena that can be used to test the chiral dynamics of QCD via ChPT. Compton scattering can be used to extract the electric and magnetic polarizabilites of the nucleon, which are fundamental structure constants. Pion photoproduction close to threshold determines the fundamental pion-nucleon amplitudes in a model-independent way. The proton polarizabilities and pion-proton threshold amplitude are in reasonable agreement with predictions. The situation for the neutron is not nearly so good, both on an experimental as well as theoretical basis. Experimental results from these programs at the Saskatchewan Accelerator Laboratory will be reviewed.
|
|
Tuesday, September 21, 1999
|
|
R. Workman
[Host: Hans Weber]
|
|
3:30 PM, Room 204
|
|
George Washington University |
| Physics Building |
|
“Topics in N* Resonance Analysis” |
|
