Bulletin of the American Physical Society
APS April Meeting 2022
Volume 67, Number 6
Saturday–Tuesday, April 9–12, 2022; New York
Session Q13: Hadronic StructureRecordings Available
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Sponsoring Units: DNP Chair: Liping Gan, University of North Carolina Wilmington Room: Empire |
Monday, April 11, 2022 10:45AM - 10:57AM |
Q13.00001: Preliminary Analysis for Pion LT Experiment in Hall C at Jefferson Lab Jacob Murphy The Pion LT Experiment is a combination of two separately-approved experiments: the measurement of the charged pion form factor to high Q2 and a scaling study for the L-T separated pion electroproduction cross section. This joint experiment allows for pion form factor extraction to the highest possible Q2, 8.5 GeV2, at Jefferson Lab. The data taken then also coincides with the scaling study at fixed xB = 0.3, 0.4, and 0.55; this will measure the Q2 dependence on the longitudinal and transverse cross sections of pion electroproduction. The latter allows for study of the transition from the non-perturbative to perturbative regions of QCD and possible transverse and regular GPD extraction. The low and mid-epsilon data collection, required for an L-T separation,completed in February 2022 at Hall C of Jefferson Lab. I will review the goals of this experiment and present preliminary analysis of the 2021-2022 data collection from both π+ and π- electroproduction up to Q2 = 8.5 GeV2. The high-epsilon data will be taken in the fall of 2022. |
Monday, April 11, 2022 10:57AM - 11:09AM |
Q13.00002: Charge Symmetry Violation Quark Distribution via Semi-inclusive Deep Inelastic Scattering in Jefferson Lab Shuo Jia Charge symmetry in the nucleon parton distributions assumes the distribution of quarks in the proton are related to those in the neutron. Indirect experimental evidence constrains Charge Symmetry Violation (CSV) to be less than 9\%. |
Monday, April 11, 2022 11:09AM - 11:21AM |
Q13.00003: First analysis of world polarized SIDIS data with small-$x$ helicity evolution Daniel M Adamiak, Yuri V Kovchegov, Daniel Pitonyak, Matthew D Sievert, Nobuo Sato, Wally Melnitchouk We use small-$x$ helicity evolution equations to analyze the world polarized DIS and Semi-inclusive DIS (SIDIS) data. After successfully describing the $g_1$ structure function extracted from polarized DIS, we extend this analysis to the small-$x$ $g^h_1$ structure function measured in polarized SIDIS. The fit is performed through a Monte-Carlo analysis within the JAM global framework. Combining the DIS and SIDIS data we are able to extract the individual helicity PDFs for both the light quarks and light anti-quarks. The advantage of our approach is that our evolution predicts the small-$x$ behavior of these helicity distributions, allowing for a precise extrapolation of our helicity PDFs to smaller values of $x$, in the region that cannot be accessed experimentally. This brings us one step closer to resolving the proton spin problem. |
Monday, April 11, 2022 11:21AM - 11:33AM |
Q13.00004: Measurement of the Neutron Electromagnetic Form Factor at High Q2 Sean Jeffas The neutron electromagnetic form factors, GnE and GnM, give important insights into the neutron structure. In previous experiments the proton electromagnetic form factors, GpE , was measured up to Q2 = 8.5 GeV2, and GpM was measured up to Q2 = 30 GeV2, while GnE has only been measured up to Q2 = 3.4 GeV2. The flavor decomposed form factors showed an unexpected Q2 scaling for the u and d quarks, but higher Q2 data is needed for the neutron. The Super BigBite Spectrometer (SBS) program at JLab plans to measure the neutron from factor ratio, GnE/GnM , at Q2 values of 1.5, 3.8, 6.8, and 10.2 GeV2 by colliding a polarized electron beam with a polarized 3He target, used here as an effective polarized neutron target, and measuring the transverse asymmetry of the cross section. This can then be used to extract the GnE values using GnM data from a companion experiment. Scattered electrons will be measured in the BigBite spectrometer while scattered neutrons will be magnetically separated from scattered protons and detected in a segmented hadron calorimeter. At the highest Q2 point the form factor ratio should be calculated with an accuracy better than ∆GnE = 3 × 10-4 , with accurate measurements of GnM. |
Monday, April 11, 2022 11:33AM - 11:45AM |
Q13.00005: Precision Measurement of the Neutron Magnetic Form Factor up to $Q^2=13.6$ $(\text{GeV}/\text{c})^2$ using BigBite and Super BigBite Spectrometers in Jefferson Lab's Hall A. Provakar Datta Nucleon elastic form factors help us understand the nucleon structure by probing their four-current distribution. But very little is known of neutron's magnetic form factor, $G^{n}_{M}$, for $Q^2 > 4$ $(\text{GeV}/\text{c})^2$. To shed some light in this area, an experiment (E12-09-019), which is currently running in Jefferson Lab's experimental Hall A, will make several high precision measurements of $G_M^n$ in the range $3 |
Monday, April 11, 2022 11:45AM - 11:57AM |
Q13.00006: Advanced extraction of the deuteron charge radius from electron-deuteron scattering data Jingyi Zhou High precision muonic deuterium spectroscopic measurements found a significantly smaller ~6σ deuteron charge radius rd compared to the radius obtained from spectroscopy of ordinary deuterium atoms and the CODATA-2014 world-average value. In order to solve this puzzle, the DRad experiment was proposed to measure the unpolarized elastic e-d scattering cross section in a very low momentum transfer squared region (Q2 = 2X10-4 - 5X10-2 (GeV/c)2), with a sub-percent proposed precision. The designed setup of the experiment will be largely based on that of the PRad-II experiment (Jefferson Lab PR12-20-004), with an addition of a low energy Si-based cylindrical recoil detector. |
Monday, April 11, 2022 11:57AM - 12:09PM |
Q13.00007: 3He and 3H Mirror Nuclei Elastic Cross Sections Leiqaa Kurbany The cross-section for elastic electron-nucleus scattering from a spin-1/2 particle is described by two nuclear form factors, fundamental quantities that describe the electromagnetic structure of the nucleus. By going to low energy and forward angle, the effect of the magnetic form factor GM(Q2) can be minimized, which allows for an extraction of the charge form factor GE(Q2) without having to do a Rosenbluth type experiment. The RMS charge radius of the nucleus is proportional to the slope, dGE(Q2) as Q2 --> 0, so by measuring the electric form factor of a target at low Q2 , we can extrapolate and extract the nucleus charge radius. |
Monday, April 11, 2022 12:09PM - 12:21PM |
Q13.00008: The short-range structure of tritium and helium-3 Shujie Li Short-range correlations (SRCs) are pairs of highly energetic nucleons generated by hard short-distance nucleon-nucleon interactions in nuclei. SRCs are an important but relatively poorly understood part of nuclear structure and mapping out the strength and isospin structure (neutron-proton vs proton-proton pairs) of these virtual excitations is thus critical input for modeling a range of nuclear, particle, and astrophysics measurements. Previous two-nucleon knockout or ``triple-coincidence'' reactions showed that SRCs are almost exclusively np pairs, but had limited statistics and required large model-dependent final-state interaction (FSI) corrections. The E12-11-112 experiment at Jefferson Lab measured the inclusive cross section of $^3$H and $^3$He. We extract the np/pp ratio of SRCs taking advantage of the isospin structure of the mirror nuclei rather than relying on measurement of final-state nucleons. The obtained np/pp SRC ratio is an order of magnitude more precise and significantly smaller than the total np dominance observed in heavy nuclei from previous experiments. This result implies an unexpected structure in the high-momentum wavefunction for $^3$He and $^3$H. Understanding these results will improve our understanding of the short-range part of the N-N interaction. |
Monday, April 11, 2022 12:21PM - 12:33PM |
Q13.00009: Spin-dependent Study Using Spectator Tagging Deuteron from Polarized $^3$He Dien T Nguyen, Richard G Milner, Xiaqing Li A polarized $^3$He target has proven a successful effective polarized neutron target for spin-dependent studies from electron scattering experiments. The structure function $g_{1}^{n}(x, Q^2)$ can be extracted from purely Deep Inelastic Scattering (DIS) inclusive measurements. We are now considering another interesting measurement in which the spectator deuteron is also detected. This measurement provides an access to the $g_{1}^{p}(x, Q^2)$ structure function from the strongly bound proton in the $^3$He nucleus. By comparing with the structure function for the free proton, we can search for possible medium modifications of the DIS spin structure, the so-called {\it spin-dependent EMC effect}. In this talk, we will present the feasibility study of such measurement using the CLAS12 spectrometer at JLab as well as at the EIC. |
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