Bulletin of the American Physical Society
2012 Fall Meeting of the APS Division of Nuclear Physics
Volume 57, Number 9
Wednesday–Saturday, October 24–27, 2012; Newport Beach, California
Session PE: Hadron Physics V |
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Chair: Oscar Rondon, University of Virginia Room: Garden II |
Saturday, October 27, 2012 10:30AM - 10:42AM |
PE.00001: A detailed study of the nuclear dependence of the EMC effect and short-range correlations J. Arrington, N. Fomin, A. Daniel, D. Day, D. Gaskell, P. Solvignon Because nucleons are closely packed in medium-to-heavy nuclei, one expects to observe density-dependent effects in their structure. Such effects can be seen in the nucleon momentum distribution in the form of a significant high-momentum tail related to the short-range interaction between nucleons, generating high-momentum short-range correlations (SRCs). High nuclear densities also imply overlap between neighboring nucleons, leading to the possible modification of their internal quark structure, which may contribute to the EMC effect. Recent Jefferson Lab experiments provided detailed information on both SRC contributions [1] and the EMC effect [2] in a range of light and heavy nuclei. We examine these results and previous data to make a detailed comparison of the A dependence of SRCs and nuclear quark distributions, along with a detailed comparison of the nuclear dependence of these two effects. We also examine the correlation between these effects, first studied in [3], in the context of different pictures of the underlying connection between these observables [4]. \\[4pt] [1] N. Fomin, et al., PRL 108 (2012) 092502\\[0pt] [2] J. Seely, et al., PRL 103 (2009) 202301\\[0pt] [3] L. Weinstein, et al., PRL 106 (2011) 052301\\[0pt] [4] J. Arrington, et al., arXiv:1206.6364 (2012) [Preview Abstract] |
Saturday, October 27, 2012 10:42AM - 10:54AM |
PE.00002: ABSTRACT WITHDRAWN |
Saturday, October 27, 2012 10:54AM - 11:06AM |
PE.00003: Study of Three-Nucleon Short Range Correlations in Inclusive Electron Scattering Zhihong Ye, Donal Day Inclusive electron scattering is a powerful tool to study short range correlations (SRCs) in nuclei. Two nucleon SRCs (2N-SRCs) were first observed in data from SLAC and further studied at Jefferson Lab, appearing, between $1.4 < x< 2$, as plateaus in the per nucleon cross section ratio of heavy to light nuclei. The Jefferson Lab experiments also provided the first evidence of three nucleon SRCs (3N-SRCs) at $x>2$. However, because of limited statistics of the earlier experiments, the scaling behavior of 3N-SRCs is not well established. Jefferson Lab experiment E08014 ran in April and May of 2011 in Hall~A and aimed to study the onset of 3N-SRCs with better accuracy and, for the first time, to examine the isospin dependence of SRCs. The experiment will be briefly described followed by a discussion of the data analysis and the presentation of the preliminary results. [Preview Abstract] |
Saturday, October 27, 2012 11:06AM - 11:18AM |
PE.00004: Nucleon structure studies through Timelike Compton Scattering Tanja Horn Hard exclusive processes have emerged as a class of reactions providing novel information on the quark and gluon distributions in hadrons. Factorization theorems allow one to express amplitudes of these processes in terms of Generalized Parton Distributions (GPDs). The measurement of suitable experimental observables and the extraction of GPDs is one of the high priority 12 GeV Jefferson Lab programs. Deeply Virtual Compton Scattering (DVCS) is generally thought of as the cleanest tool for accessing the valence quark GPDs of the nucleon. A new and promising opportunity on the road to constraining GPDs is presented by Timelike Compton scattering (TCS) the inverse process to space-like DVCS. TCS offers straightforward access to the real part of the Compton amplitude. Combining space-like and time-like data thus makes it possible to test the universality of GPDs. The first studies of TCS using real tagged and quasi-real untagged photons were performed at Jefferson Lab 6 GeV. In this talk preliminary results on angular asymmetries and extraction of the real part of Compton form-factors using electroproduction data and a comparison with photoproduction data will be presented. We will also discuss future plans for di-lepton production in the Jefferson Lab 12-GeV era. [Preview Abstract] |
Saturday, October 27, 2012 11:18AM - 11:30AM |
PE.00005: Peripheral Transverse Densities of the Nucleon in a Chiral-Parton Approach to Isovector Form Factors Carlos Granados, Christian Weiss We calculate the nucleon's isovector electromagnetic and gravitational form factors using leading time ordered diagrams in the infinite momentum frame. These form factors can be written as overlaps of nucleon-pion light-cone wave-functions of the nucleon plus, in the case of electromagnetic form factors, a non-partonic contact term. We demonstrate also that through Fourier transforms, these form factors are related to transverse charge densities of the nucleon that are calculable in the nucleon's periphery using an isovector pion-nucleon coupling when calculating wave functions. It is found that these transverse densities are suppressed exponentially at large distances by powers that grow with the pion's longitudinal momentum. Both, electromagnetic and gravitational form factors along with the corresponding transverse densities in this partonic approach will further characterize the chiral contribution to the nucleon's internal orbital angular momentum. [Preview Abstract] |
Saturday, October 27, 2012 11:30AM - 11:42AM |
PE.00006: Dihadron Correlation in the eA program at an Electron Ion Collider Liang Zheng Deep inelastic scattering (DIS) experiments, in which one probes the internal landscape of the proton or nucleus by scattering a lepton on it, are a very powerful tool to study QCD. Past results from HERA were very successful in determining the quark structure of a nucleon and some light nuclei. Meanwhile gluons, which are responsible for the quark confinement and much of the hadronic mass, are significantly less well-understood than quarks, especially in the saturation regime, where their self-interactions dominate and non-linear QCD effects supersede. In the future, a high energy, high luminosity Electron-Ion Collider (EIC) may prove essential to help us to unveil the profound collective behavior of densely packed gluons deep into the saturation region. Being sensitive to the gluon dynamics, dihadron correlations are believed to be one of the most compelling measurements in the eA program at EIC to identify and characterize saturation physics. In this talk, I am going to discuss some Monte Carlo simulation results of dihadron correlation in e+A collisions and compare with theoretical calculations in the context of gluon saturation for the proposed EIC at Brookhaven National Lab. [Preview Abstract] |
Saturday, October 27, 2012 11:42AM - 11:54AM |
PE.00007: eRHIC as a Nucleon Tomograph Thomas Burton eRHIC is planned as a state-of-the-art Electron-Ion Collider, to be located at Brookhaven National Lab as a major expansion to the existing RHIC complex by the addition of a high-intensity electron beam. The well-understood nature of the electron probe and the extreme luminosity of the eRHIC machine, one thousand times greater than that of HERA, will provide an exquisitely precise characterisation of nucleonic matter and its interactions. By studying both exclusive and semi-inclusive interactions, eRHIC will probe the distribution and motion of partons (quarks and gluons) within the nucleon. With high polarisation of the electron and proton beams, the spin-dependence of these distributions will also be studied. It will allow a detailed tomographic imaging of matter, analogous to MRI and CT technology used in medicine, but at a scale of less than one femtometre. This ``nucleon femtoscope'' will provide us with a novel look at the smallest of scales of the material that composes the visible universe. [Preview Abstract] |
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