Bulletin of the American Physical Society
APS April Meeting 2022
Volume 67, Number 6
Saturday–Tuesday, April 9–12, 2022; New York
Session D09: Mini-Symposium: Nucleon Structure and PDFs at Large xMini-Symposium Recordings Available
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Sponsoring Units: GHP Chair: David Gaskell, Jefferson Lab/Jefferson Science Associat Room: Juilliard |
Saturday, April 9, 2022 1:30PM - 2:06PM |
D09.00001: Recent Results in Nucleon Structure at Large x Invited Speaker: Arun Tadepalli
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Saturday, April 9, 2022 2:06PM - 2:18PM |
D09.00002: Interplay of higer-twist and off-shell corrections in global QCD fits at large x Shujie Li, Ishara P Fernando, Alberto Accardi We will show how, in a global QCD analysis that includes DIS data on deuteron targets, the fit of the d-quark PDF and the extraction of the neutron structure function at large x values can be heavily biased by theoretical assumptions. In particular, we will focus on the interplay of higher-twist effects and off-shell PDF deformations in deuteron targets, and show that: (1) the available hard scattering data are sufficient to independently fit higher-twist corrections to proton and neutron structure functions, and (2) doing so removes most of the theoretical bias. The result is a stable fit of: the d/u quark ratio, that tends to a small but non-zero value as x tends to 1; the extracted free neutron F2 structure function; and (3) the off-shell PDF deformation function. |
Saturday, April 9, 2022 2:18PM - 2:30PM |
D09.00003: Measurements of the Inclusive Electron Scattering off Protons with CLAS12 Valerii Klimenko Electron scattering data off protons from the CLAS12 detector in Hall B at Jefferson Laboratory have become available and cover a wide kinematic range in W up to 2.5 GeV and Q2 up to 10 GeV2, offering new opportunities to explore inclusive, semi-inclusive, and fully exclusive reactions. A study that aims to extract the inclusive electroproduction cross sections from the CLAS12 data collected at a beam energy of 10.6 GeV from an unpolarized liquid-hydrogen target is now almost finished and preliminary results will be presented. Because of the large acceptance of CLAS12, these data offer a unique opportunity to measure inclusive cross sections at W from the meson electroproduction threshold to 2.5 GeV within any given Q2-bin. This unique W- coverage at fixed Q2-values is of particular importance for the extension of our knowledge on the nucleon parton distribution function from the data on F2 structure function in the resonance region by employing the existing CLAS results on the γpN* electroexcitation amplitudes. These studies also offer valuable input for the exploration of quark-hadron duality. |
Saturday, April 9, 2022 2:30PM - 2:42PM |
D09.00004: Measuring the Neutron Spin Asymmetry A1n in the Valence Quark Region in Hall C at Jefferson Lab Melanie Cardona, Zein-Eddine Meziani Due to the non-perturbative nature of QCD, making absolute predictions of nucleon spin structure is generally difficult. While successful lattice QCD calculations of spin and orbital angular momentum (OAM) of the quarks and gluons, integrated over their longitudinal momentum fraction (xbj), exist, there remains much to learn about their xbj-dependence. With the breakthrough of the quasi-PDFs formalism, confronting ab-initio calculations of unintegrated spin observables including OAM will be possible. The neutron spin asymmetry A1n at high xbj is a key observable for probing nucleon spin structure since in the valence domain (xbj > 0.5) sea effects are expected to be negligible, where the total nucleon spin is considered to be carried by the valence quarks, and can enable us to study the role of quark OAM and other non-perturbative effects of the strong force. A1n was measured in the deep inelastic scattering region of 0.30 < x < 0.75 and 3 < Q2 < 10 (GeV/c)2 in Hall C at Jefferson Lab using a 10.4 GeV longitudinally polarized electron beam, upgraded polarized 3He target, and the High Momentum Spectrometer (HMS) and Super High Momentum Spectrometer (SHMS). The wide Q2 range will explore possible Q2 dependence on A1n, provide the first precision data in the valence quark region above xbj = 0.61, and therefore test various predictions and ultimately ab-initio lattice QCD calculations. |
Saturday, April 9, 2022 2:42PM - 2:54PM |
D09.00005: Polarized $^3$He Target in High Magnetic Field at CLAS12 Xiaqing Li, James D Maxwell, Dien T Nguyen A nuclear spin polarized $^3$He target has been successfully used for decades to measure spin-dependent electron scattering from the neutron. In addition, the $^3$He nucleus has a rich spin structure that is complementary to that of the deuteron and can be calculated with high precision. Polarized $^3$He targets in low magnetic fields have been well developed using the spin exchange optical pumping technique. However, the application of a polarized $^3$He target in a high-magnetic-field environment is limited due to the increased wall relaxation. Taking advantage of recent improvements in high-field metastability exchange optical pumping, a novel double-cell cryogenic target has been designed to accommodate to the 5-T solenoid in Hall B at Jefferson Lab for a proposed experiment of spin-dependent electron scattering from a polarized $^3$He target at CLAS12. In this talk, we will present the results from the low-field (30 Gauss) tests. In addition, we will present the path toward the high-field tests with preliminary results. |
Saturday, April 9, 2022 2:54PM - 3:06PM |
D09.00006: Quark-quark correlations in the nucleon at high x in the residual mean field model Christopher A Leon, Misak M Sargsian, Joseph E Maerovitz In previous work, we modeled the nucleon by separating it into valence and residual structures. We described the valence quarks as just moving in a mean field. We now incorporate quark-quark correlations to the model to describe the high x structure of valence quarks in the nucleon. The calculations are performed using perturbative quantum chromodynamics in a light front effective diagrammatic framework. PDFs are extracted from our extended model and our results are compared existing PDF sets. |
Saturday, April 9, 2022 3:06PM - 3:18PM |
D09.00007: Unpolarized Isovector Nucleon PDF from LaMET Yushan Su Large Momentum Effective Theory (LaMET) can be used to extract parton physics from lattice QCD calculation. It has a wide range of applications since its proposal, including PDF, TMD, DA, and GPD. Unpolarized isovector nucleon PDF has been widely studied in high precision through global fit with experimental data. So it is a natural benchmark to test LaMET and lattice calculation on the ability to control the systematic errors. Under LaMET framework, we present the lattice calculation of unpolarized isovector nucleon PDF on CLS ensembles H102 (a=0.0854fm), N203 (a=0.0644fm), and N302 (a=0.0500fm). The nucleon momentum is from 2.3 to 3.2 GeV. We adopt the Hybrid renormalization scheme with self-renormalization, which can eliminate the UV divergence without introducing extra non-perturbative effects. We adopt two-loop matching, which leads to a similar result with one-loop matching. As the momentum becomes larger, PDF from lattice calculation becomes consistent with PDF from global fit. Moreover, we find that there is more d_bar than u_bar up to x~0.3 in our calculation, which is consistent with experimental results of antimatter asymmetry. |
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