Bulletin of the American Physical Society
2011 Fall Meeting of the APS Division of Nuclear Physics
Volume 56, Number 12
Wednesday–Saturday, October 26–29, 2011; East Lansing, Michigan
Session JC: Hadronic Physics II |
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Chair: Igor Strakovsky, The George Washington University Room: 101 |
Friday, October 28, 2011 2:00PM - 2:12PM |
JC.00001: HAPPEX-III results: measurement of nucleon strange form factors at high Q$^2$ Rupesh Silwal The bare mass of the three valence quarks only makes $\sim$1\% of the proton mass, the rest is gluons and a sea of quarks and anti-quarks dominated by the light up, down and strange stark flavors. From a naive interpretation of the quark model, one might expect that the electromagnetic from factors are determined only by the distribution of valence quarks. But, existing data suggesting a no-zero strange quark contribution to these form factors at high Q$^2$ has been a topic of great interest. Recent results from HAPPEX-III collaboration have significantly clarified the role of intrinsic strangeness in the nucleon vector form factors; these results will be presented and discussed. [Preview Abstract] |
Friday, October 28, 2011 2:12PM - 2:24PM |
JC.00002: Recent Results in Parity-Violating Electron Scattering at Jefferson Lab: PREX and HAPPEX-III Chun-Min Jen The parity-violating asymmetry $A_{PV}$ in electron scattering from the $^{208}$Pb nucleus is cleanly sensitive to the neutron radius $R_n$. A precision measurement of $R_n$ would have important implications for the understanding of nuclear structure, and be a powerful constraint on the symmetry energy $S_{\nu}(n)$ of neutron-rich nuclear matter, including neutron stars. The PREX collaboration has completed a first run, measuring $R_{n}$ to a precision of $\sim2.5$\% and providing the first electroweak evidence for the neutron skin of a heavy nucleus. Results from this measurement, and prospects for more precise future measurements, will be discussed. [Preview Abstract] |
Friday, October 28, 2011 2:24PM - 2:36PM |
JC.00003: ABSTRACT WITHDRAWN |
Friday, October 28, 2011 2:36PM - 2:48PM |
JC.00004: Study of the ${\rm {}^4 He(e,e^{\prime}p)}$ reaction up to high missing momenta and energies. Search for N-N Short Range Correlations Fatiha Benmokhtar The ${\rm {}^4He(e,e^{\prime}p)}$ reaction has been recently measured up to high missing momenta and missing energies; ${\rm p_m~of~ 1~GeV/c}$ and ${\rm E_m~ of ~ 200~ MeV}$, respectively, in Hall A of Jefferson Lab., part of a rich short range correlation experimental program. The continuum region is under study in order to investigate high-nucleon-momenta components in the ${\rm {}^4 He}$ wave function with the absorption of virtual photons on nucleons correlated in pairs in the ${\rm {}^4 He}$ ground state. The measurements were performed at $x_B = 1.25$ and at a fixed transferred four-momentum ${Q^2}=2(GeV/c)^2$. Physics goals will be discussed and analysis status and strategy will be presented. [Preview Abstract] |
Friday, October 28, 2011 2:48PM - 3:00PM |
JC.00005: Measurements of the helicity asymmetry E for eta meson photoproduction on the proton Brian Morrison The nucleon resonance spectrum consists of many overlapping excitations. Polarization observables are an important tool for understanding and clarifying these spectra. While there is a large data base of differential cross sections for the process, there are no published data for eta double polarization asymmetries. A program of double polarization experiments has been conducted at Jefferson Lab using a tagged polarized photon beam and a frozen spin polarized target (FROST). The results to be presented were taken during the first running period of FROST using the CLAS detector at Jefferson Lab with photon energies ranging from 329 to 2,350 MeV. We present data for the E polarization observable for eta meson photoproduction at threshold and above, along with comparisons to several theoretical predictions. [Preview Abstract] |
Friday, October 28, 2011 3:00PM - 3:12PM |
JC.00006: Transverse Polarization of $\Sigma^{+}(1189)$ in Photoproduction on Hydrogen Target with CLAS Chandra S. Nepali, Moskov Amaryan Experimental results on the measurement of $\Sigma^{+}(1189)$ hyperon transverse polarization in photoproduction on a hydrogen target with CLAS are presented for the first time. The $\Sigma^{+}(1189)$ is reconstructed in the exclusive reaction $\gamma+p \rightarrow K_{S} \Sigma^{+}(1189)$ via the decay $\Sigma^{+} \rightarrow p \pi^0$. The $K_{S}$ is reconstructed in the invariant mass of two oppositely charged pions and $\pi^0$ is identified in the missing mass of detected proton, $\pi^+$ and $\pi^-$. We observe significant negative polarization of as much as 60$\%$. Experimental data are collected in the photon energy range 1-3.5 GeV. As the mechanism of large transverse polarization of hyperons produced in unpolarized hadro-, and photo production experiments is still not well understood, these results will help to distinguish between different theoretical models on hyperon production. Current status of the analysis and future prospects are discussed. [Preview Abstract] |
Friday, October 28, 2011 3:12PM - 3:24PM |
JC.00007: Light Anti-quark Asymmetry in E906 Drell-Yan ($p+p(d)\rightarrow\mu^++\mu^-$) and prospects of polarized Drell-Yan at Fermilab Main Injector Chiranjib Dutta The E-906/SeaQuest experiment will measure the Drell-Yan cross section in p-p and p-d scattering and will determine the $\frac{\bar{d}}{\bar{u}}$ asymmetry over 0.04 $<$ x $<$ 0.45, thus extending the available E-866 measurements to a higher x region. The experiment will use the 120 GeV/c proton beam extracted from the Fermilab Main Injector on liquid hydrogen and deuterium targets which will provide a significant improvement in the statistical uncertainty as compared to the predecessor E-866 measurements. The experiment will start taking data in the summer of 2011. Efforts are currently underway to study the feasibility of using the E906 spectrometer together with a polarized proton beam in the Main Injector or/and a polarized proton target for polarized Drell-Yan scattering. This would allow to measure the transverse momentum dependent degrees of freedom in the nucleon via single spin asymmetries (SSA). The most anticipated result from polarized Drell-Yan will not only complement existing results from SIDIS measurements, but also serve as an independent check of a fundamental prediction of QCD. The current status of preliminary data taking as well the expected results from E906/SeaQuest experiment will be addressed. The physics motivation and the prospects of the next generation polarized Drell-Yan experiment in Fermilab will be discussed. [Preview Abstract] |
Friday, October 28, 2011 3:24PM - 3:36PM |
JC.00008: Comparison of kaon and pion valence quark distributions in a statistical model Mary Alberg We have calculated the Bjorken-$x$ dependence of the kaon and pion valence quark distributions in a statistical model. Each meson is described by a Fock state expansion in terms of quarks, antiquarks and gluons. Although the pion valence quark distributions have been determined by Drell-Yan experiments, the kaon valence quark distributions have only been deduced from the measurement of the ratio $\bar{u}_K(x)/\bar{u}_\pi(x)$ by Badier et al. [1]. We show that, using no free parameters, our model is in good agreement with the decrease of this ratio with increasing $x$. \\[4pt] [1] J. Badier et al., Phys. Lett. B 93 (1980) 354. [Preview Abstract] |
Friday, October 28, 2011 3:36PM - 3:48PM |
JC.00009: Precision Measurement of Charged Hadron Multiplicities in $e^{+}e^{-}$ Annihilation at Belle Martin Leitgab Fragmentation functions describe the formation of final state particles from a partonic initial state. Precise knowledge of these functions is a key ingredient in accessing quantities such as the nucleon spin structure in semi-inclusive deep inelastic scattering and proton proton collisions. However, fragmentation functions can currently not be determined from first principles Quantum Chromodynamics and have to be extracted from experimental data. The Belle experiment at KEK, Japan, provides a large data sample at a low energy scale for high precision measurements of hadron multiplicities allowing for first-time or more precise extractions of fragmentation functions. The current status of the measurement will be presented. [Preview Abstract] |
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