Bulletin of the American Physical Society
APS April Meeting 2019
Volume 64, Number 3
Saturday–Tuesday, April 13–16, 2019; Denver, Colorado
Session X09: Valence- and Sea-Quark Structure of the Nucleon |
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Sponsoring Units: GHP DNP Chair: Ramona Vogt, rlvogt@lbl.gov Room: Sheraton Governor's Square 11 |
Tuesday, April 16, 2019 10:45AM - 10:57AM |
X09.00001: Free neutron structure function at large x Bjorken region Sooriyaarachchilage Aruni Nadeeshani While the structure of the proton has been studied extensively through inelastic electron scattering, much less is known about neutron structure due to the unavailability of high density, free neutrons targets. The BONuS12 experiment was proposed to measure the neutron structure function on a nearly free neutron via the spectator tagging method by tagging the slow backward moving proton. The spectator proton is used to interpret initial momentum of the weakly bound neutron in deuterium atom. A recoil detector will be used to detect spectator protons with momenta $70< P<150 $ MeV/c and the CEBAF Large Acceptance Spectrometer (CLAS12) to detect the scattered electrons. In this talk I will present the design of the recoil detector(RTPC), which was lead by Hampton University, as well as construction and prototyping performed on campus. |
Tuesday, April 16, 2019 10:57AM - 11:09AM |
X09.00002: Nucleon Structure Function at large Bjorken x from 12 GeV commissioning experiment E12-10-002 in Hall C Debaditya Biswas Measurement of F2 Structure Function from inclusive inelastic electron-nucleon scattering cross section have been important for the study of QCD structure of proton. E12-10-002 is one of the commissioning experiments ran in Hall C to measure the electron-nucleon scattering cross sections in the Q2 range of 4 to 17 GeV2 . This experiment covers a wide range of Bjorken x including the Large Bjorken x where existing data lacks statistical precision. This requires precision measurements of charge from the Beam Charge Monitoring (BCM) study and the the efficiency of the tracking detector. I will discuss an overview of the experiment along with current status of charge measurement from Beam Charge Monitoring study and the study of efficiency of the tracking detector. |
Tuesday, April 16, 2019 11:09AM - 11:21AM |
X09.00003: Preliminary results of cross sections measurements from E12-10-002 in 12 GeV era at Jefferson Lab Abel Sun Measurements of H(e,e') and D(e,e') cross sections were done at Jefferson Lab in experimental Hall C in Spring 2018. As part of the 12 GeV early running, we took data to explore a wide range in Bjorken x and to reach a four-momentum transfer Q2 of up to 17 GeV2. In this talk, I will show the preliminary results of our analysis and I will summarize the expected physics output. |
Tuesday, April 16, 2019 11:21AM - 11:33AM |
X09.00004: Towards a combined analysis of inclusive/exclusive electroproduction Astrid Hiller Blin, Adam P Szczepaniak, Victor I Mokeev The CLAS experiments have achieved major advances in the study of the $N^*$ region of the electroproduction spectrum. Data on electrocouplings of the many baryon resonances in the mass range up to 1.8 GeV showed consistency between the $N\pi$, $N\eta$ and $N\pi^+\pi^-$ channels. |
Tuesday, April 16, 2019 11:33AM - 11:45AM |
X09.00005: Direct Measurement of Initial-State Energy Loss in Cold Nuclear Matter at Fermilab E906/SeaQuest Sho Uemura The study of parton energy loss in cold nuclear matter is crucial for understanding the nuclear medium properties in heavy ion experiments. The nuclear modification RpA of the Drell-Yan process is a clean channel for measuring initial-state quark energy loss. The E906/SeaQuest experiment at the Fermilab Main Injector measures Drell-Yan, J/ψ, and ψ' production for p+A collisions with H, D, C, Fe, and W targets. The proton beam energy of 120 GeV (√sNN=15 GeV) amplifies the expected energy loss effects relative to previous experiments with higher beam energies. The spectrometer acceptance is optimal for large target x where other nuclear effects, such as shadowing, are expected to be small. We present the current status of this measurement. |
Tuesday, April 16, 2019 11:45AM - 11:57AM |
X09.00006: Charge Symmetry Violation in Quark Distributions using Semi-Inclusive Deep Inelastic Scattering (SIDIS) Hem D Bhatt
The invariance of the strong interactions during specific isospin rotation of 180 degrees, with the exchange of up and down quarks, while simultaneously interchanging protons and neutrons, is known as charge symmetry. It has generally been assumed to be valid in most parton distribution fits. The violation of this symmetry arises due to the small mass difference between up and down quarks and the electromagnetic interactions. Although charge symmetry violation (CSV) is expected to be very small, the precision of the existing data can only constrain it to be < ± 10%. Jefferson Lab Hall-C experiment E12-09-002 aims to place constraints on the degree of CSV in the valence quark distributions in the nucleon via semi-inclusive deep inelastic scattering. In this experiment, a 10.6 GeV electron beam incident on a liquid deuterium target with the scattered electrons and charged pions detected in coincidence in the HMS and SHMS spectrometers respectively. This experiment will measure the ratios of charged pion cross-sections with high precision to extract and place limits on the charge symmetry violating parton distribution. The current status of this experiment as well as the quality of the collected data will be discussed in this talk.
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Tuesday, April 16, 2019 11:57AM - 12:09PM |
X09.00007: Recent progress on studies of Light Quark Flavor Asymmetry at SeaQuest Experiment Arun Tadepalli The Fermilab E906/SeaQuest is an experiment aimed at studying the anti-quark distributions in nucleons and nuclei. The experiment uses a 120 GeV proton beam extracted from the Main Injector at Fermilab. SeaQuest takes advantage of the Drell-Yan process to probe the anti-quark structure in the proton. In the Drell-Yan process, quark from one hadron annihilates with an anti-quark from another hadron, producing a virtual photon which eventually decays into dileptons. The SeaQuest forward spectrometer is designed to detect such dimuons generated by the Drell-Yan process. Ratio of cross-sections of the interaction of proton beam on liquid deuterium and hydrogen targets allows SeaQuest to map out dbar(x)/ubar(x) up to a region of ~0.45 in Bjorken-x, a region which hasn't been explored yet. Recent progress on the data analysis for dbar(x)/ubar(x) will be presented in this talk. |
Tuesday, April 16, 2019 12:09PM - 12:21PM |
X09.00008: Strange crossings in the proton sea Mary Alberg Net strangeness in the proton is zero, but the momentum distributions of the s and sbar quarks in the proton sea may differ. This strangeness asymmetry, s(x)-sbar(x), arises from fluctuations of the proton into meson-baryon pairs. We use a Fock state expansion of the proton, in terms of K-Lambda, K-Sigma, K*-Lambda, and K*-Sigma states, to represent this “strange meson cloud”, in which s quarks reside in baryons and sbar quarks in mesons. We determine the momentum distributions of the strange quarks in a hybrid convolution model, in which the fluctuations are represented either by light-cone or meson-baryon splitting functions. For the parton distributions of the s(sbar) quarks in the “bare” baryons(mesons) of the Fock states, we use light cone wave functions or our statistical model, which expands the bare hadrons in terms of quark-gluon states. We present our results for strangeness asymmetry, which include one or more zero crossing points, and compare them to global parton distributions and other theoretical work. |
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