Bulletin of the American Physical Society
2021 Fall Meeting of the APS Division of Nuclear Physics
Volume 66, Number 8
Monday–Thursday, October 11–14, 2021; Virtual; Eastern Daylight Time
Session KK: DIS and Photoproduction |
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Chair: Andrei Afanasev, George Washington University Room: Arlington |
Wednesday, October 13, 2021 11:30AM - 11:42AM |
KK.00001: Relations among TMDs in the Parton Model Aditi D Mahabir, Fatma Aslan, Saman Bastami, Peter J Schweitzer Transverse momentum dependent parton distribution functions (TMDs) play an important role for the description of deep-inelastic scattering processes, and constitute important parts of the experimental programs at BNL, Jefferson Lab and the future Electron-Ion Collider. While some TMDs are well-studied, much less is known about other TMDs. One helpful guideline in this situation is the use of models like the covariant parton model, which predicts many interesting relations among different TMDs. In this contribution, we report results of a study of the relations among TMDs in the covariant parton model. |
Wednesday, October 13, 2021 11:42AM - 11:54AM |
KK.00002: First evidence for isovector EMC effect from global QCD analysis with MARATHON data Wally Melnitchouk, Christopher Cocuzza, Cynthia E Keppel, Hanjie Liu, Andreas Metz, Nobuo Sato, Anthony W Thomas AC We report the results of a Monte Carlo global QCD analysis of unpolarized parton distribution functions (PDFs), including for the first time constraints from ratios of 3He to 3H structure functions recently obtained by the MARATHON experiment at Jefferson Lab. Our simultaneous analysis of nucleon PDFs and nuclear effects in A=2 and A=3 nuclei reveals the first indication for an isovector nuclear EMC effect in light nuclei. We find that while the MARATHON data yield relatively weak constraints on the F2n/F2p neutron to proton structure function ratio and the d/u PDF ratio, they suggest a strongly enhanced nuclear effect on the d-quark PDF in the bound proton. |
Wednesday, October 13, 2021 11:54AM - 12:06PM |
KK.00003: General Tensor Structure for Inclusive and Semi-inclusive Electron Scattering from Spin-1/2 Targets Sabine E Jeschonnek, Thomas W Donnelly, J. W Van Orden We study inclusive and semi-inclusive polarized electron scattering from polarized spin ½ targets. These reactions are of interest for experiments at fixed target accelerators like CEBAF at Jefferson Lab, and the planned electron-ion collider (EIC). We find that there are four sectors which may be separated by employing beam and target polarizations. When unpolarized electrons are used, only symmetric tensors enter, whereas antisymmetric tensors enter for longitudinally polarized electron beams. In the different sectors, we identify a total of 18 invariant response functions which depend on four Lorentz scalars. We classify these according to their properties under parity and time reversal. |
Wednesday, October 13, 2021 12:06PM - 12:18PM |
KK.00004: Deeply learning deep inelastic scattering kinematics Abdullah Farhat, Markus Diefenthaler, Yuesheng Xu We studied the use of machine learning to reconstruct deep inelastic scattering (DIS) kinematics in exclusive processes. In particular, we trained deep neural networks to reconstruct x, Q2, and t, based on full information from ep scattering using CLAS 12 data from Jefferson Lab. These models were trained by a careful selection of Monte Carlo events. The results from the neural networks were compared to those of classical reconstruction methods, which only consider partial information from an event and, thusly, have limitations, including a sensitivity to initial and final state QED radiation, a requirement of precise energy measurements, and/or a poor resolution on different kinematic regions. The neural networks trained in our study reconstruct event kinematics based on the information used in the classical methods, but, in addition, are enhanced through correlations and patterns revealed in the simulated data sets from event generators. |
Wednesday, October 13, 2021 12:18PM - 12:30PM |
KK.00005: Delta baryon photoproduction with twisted photons Carl E Carlson, Andrei Afanasev A future gamma factory at CERN or accelerator-based gamma sources elsewhere can include the possibility of energetic twisted photons, which are photons with a structured wave front that can allow a pre-defined large angular momentum along the beam direction. Twisted photons are potentially a new tool in hadronic physics, and we consider here one possibility, namely the photoproduction of Delta(1232) baryons using twisted photons. We show that particular polarization amplitudes isolate the smaller partial wave amplitudes and they are measurable without interference from the terms that are otherwise dominant. |
Wednesday, October 13, 2021 12:30PM - 12:42PM |
KK.00006: Exclusive φ Meson Electroproduction with CLAS12 Brandon A Clary The Continuous Electron Accelerator Facility Large Angle Spectrometer detector (CLAS12) at Jefferson Lab |
Wednesday, October 13, 2021 12:42PM - 12:54PM |
KK.00007: Photoproduction of Λ* Resonances Using the CLAS Detector Utsav Shrestha, Kyungseon Joo
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Wednesday, October 13, 2021 12:54PM - 1:06PM |
KK.00008: Compton Scattering Cross Section Measurement in Hall D at Jefferson Lab Andrew P Smith The PrimEx-Eta fixed-target experiment in Hall D at Jefferson Lab (E12-10-011) will measure the η→γγ decay width using the Primakoff method with a projected uncertainty of 3.2%. In order to achieve this goal, Compton scattering from the atomic electrons in the target is being used as a reference process. Because of its similar kinematics to the η→γγ decay, the total Compton scattering cross section can be measured using the same experimental configuration as the η decay width measurement. Thus, it can be used to verify the systematic uncertainties for the η decay width measurement and monitor the luminosity, detection efficiency, and overall experimental stability. The first phase of the PrimEx-Eta data was collected in 2019, corresponding to roughly one-third of the total proposed statistics. In this talk, I will discuss the preliminary results for the total Compton scattering cross section measured on a 9Be target as well as a liquid 4He target. |
Wednesday, October 13, 2021 1:06PM - 1:18PM |
KK.00009: Measurement of Elastic Electron Scattering Transverse Asymmetries on 1H, 12C and 27Al Gregory R Smith We report measurements of the parity-conserving beam-normal single-spin elastic scattering asymmetries Bn on 1H, 12C and 27Al, obtained with an electron beam polarized transverse to its momentum direction. These measurements add an additional kinematic point to a series of previous measurements of Bn on 1H and 12C, and provide a first measurement on 27Al. The experiment utilized the Qweak apparatus at Jefferson Lab with a beam energy of ~1.15 GeV. The average laboratory scattering angle was 7.8°, and the average Q2 was 0.024 GeV2 (Q = 0.156 GeV). The results are consistent with theoretical predictions, and are compared to existing data. The 1H result is the most precise measurement of Bn to date and therefore provides a stringent test of two-photon exchange models at far-forward scattering angles (θlab→0) where they should be most reliable. When scaled by Z/A, the Q dependence of all the far-forward angle (q <10°) data from 1H to 27Al can be described by the same slope out to Q = 0.35 GeV. Larger-angle data from other experiments in the same Q range are consistent with a slope about twice as steep. |
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