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 LF: Mini-Symposium: Advances and Opportunities in Polarized Targets and Beams III |
Hide Abstracts |
Chair: Ishara Fernando, UVA/Fermilab Room: Berkeley & Clarendon |
Wednesday, October 13, 2021 2:00PM - 2:12PM |
LF.00001: Spin effects and two-photon exchange in low-energy electron-nucleon scattering: New theoretical developments Jose L Goity, Christian Weiss, Cintia Willemyns The transverse single-spin asymmetry in inclusive electron-nucleon scattering, e + N(ST)→ e’ + X, represents a pure two-photon exchange observable and is of fundamental interest for exploring higher-order QED effects in electron scattering. We compute this observable in the resonance region, where excitation of Δ isobars occurs in both intermediate and final states. We employ a novel theoretical method based on the large-Nc limit of QCD, which allows us to consistently combine N and Δ states and predict the elastic, inelastic, and inclusive spin-dependent cross section. Our results explain the contributions of N and Δ states and the Nc-scaling of the transverse spin asymmetry. Our predictions could be tested in future measurements of electron-nucleon scattering with polarized targets in the few-GeV energy range. Such experiments would complement earlier measurements of the inclusive single-spin asymmetry in the DIS regime (JLab, HERMES) and allow one to study the unknown dependence of two-photon exchange dynamics on the energy/momentum of the probe. |
Wednesday, October 13, 2021 2:12PM - 2:24PM |
LF.00002: Neutron Spin Structure from e-3He Scattering with Double Spectator Tagging at the Electron-Ion Collider Jackson R Pybus The spin structure function of the neutron is traditionally determined by measuring the spin asymmetry of inclusive electron deep-inelastic scattering (DIS) off polarized 3He nuclei. In such experiments, correcting for nuclear effects can introduce large systematic uncertainties and model-dependencies. This talk presents our study of the feasibility of suppressing such model dependencies by tagging both spectator protons in the process of DIS off neutrons in 3He at the forthcoming Electron-Ion Collider (EIC). This allow us to reconstruct the momentum of the struck neutron to ensure it was nearly on-shell in the initial state, thereby reducing sensitivity to nuclear corrections, and suppressing contributions from electron DIS off protons in 3He. We find that the EIC can probe the neutron spin structure from $x_B$ of 0.003 to 0.0651. We further find that the double spectator tagging method results in reduced uncertainties by a factor of 4 on the extracted neutron spin asymmetries over all kinematics, and by a factor of 10 in the low-$x_B$ region, providing high-precision data that will give insight into the spin structure of the nucleon. Special emphasis will be given to the incorporation of nuclear motion in the event modeling. |
Wednesday, October 13, 2021 2:24PM - 2:36PM |
LF.00003: Photon Beam Polarimetry Using Detection of e+e- Pairs at GlueX Andrew Schick Bethe-Heitler e+e- pair production provides an important method for determining photon beam polarizations. Conventional techniques are pair production on atomic electrons (triplet polarimeter, TPOL) and pair production on a nuclear target with detection of one lepton. For the Charged Pion Polarizability (CPP) experiment at GlueX there is a need for a precision cross-check on TPOL that can be synchronous with data taking. In this talk we present a new technique and result for measurement of linear beam polarization through the detection of both e+and e- in the forward drift chambers and calorimeters of the GlueX detector. The polarized form of the Bethe-Heitler cross-section shows that the analyzing power for the azimuthal distribution of e+e- is 60% in the kinematics of the CPP experiment. Using a neural net for e/π separation, we analyzed the GlueX 2018-01 data set and measured an average beam polarization of 0.325 ± 0.007. This result is within 2σ of the polarization from the TPOL measurement. Obtaining linear beam polarization from e+e- events produced during data taking can be applied in photo-production experiments where detection of e+e- pairs is achieved with good particle ID. |
Wednesday, October 13, 2021 2:36PM - 2:48PM |
LF.00004: Exploring fundamental properties of 3He through the polarized 3He(e,e'd) process in CLAS12 Douglas W Higinbotham, Dien T Nguyen, Or Hen, Simon Sirca Spectrometer measurements of the (e,e’p) and (e,e’d) quasi-elastic processes on polarized 3He have revealed deficiencies in our understanding of the three-body system. With the limited kinematic coverage of these experiments, it has been impossible to disentangle which aspects of the theoretical description are problematic. While resolving these problems is interesting from a purely few-body physics point of view, it is also of critical importance to our interpretation of deep-inelastic data from polarized 3He which is often used as an effective polarized neutron target. A new idea to measure these reactions in CLAS12 with a new meta-stability exchange optical pumped 3He target. This new data, which will cover an extremely board range of kinematics, should allow determination of which model ingredients such as the choice of the NN force, relevance of the three-nucleon force, final-state interactions, and/or meson-exchange currents need to be improved. |
Wednesday, October 13, 2021 2:48PM - 3:00PM |
LF.00005: Analysis of Dilution Factor in Drell Yan and J/psi Production Shyh-Tse Linus Chiou With the use of modern parton level cross-section generators, we can analyze the contributions from unmeasured cross-sections from these various materials to find the degree of dilution and the corresponding kinematic sensitivity. Data provided by earlier Drell-Yan experiments is used to fine-tune the distributions in the phase-space of interest and set the simulation input parameters. In addition, the SpinQuest experiment will also measure the Transverse Single Spin Asymmetry for J/psi production. In this presentation, I will talk about the projection of the dilution factor for both Drell-Yan and J/psi production and the expected impact on the overall systematic error in the SpinQuest experiment. |
Wednesday, October 13, 2021 3:00PM - 3:12PM |
LF.00006: A program of Spin-dependent study using electron scattering from a Polarized 3He Target in CLAS12 Dien T Nguyen, Richard G Milner, James D Maxwell, Harut Avagyan This talk will present an exciting physics program of spin-dependent study using the CLAS12 spectrometer in Hall B at Jefferson Lab. The proposal will use a 10.6 GeV electron beam incident on a novel polarized 3He target to do high precision measurements for both spin-dependent inclusive and semi-inclusive DIS (π±, K±) over a large kinematic range: 0.05 < x < 0.7, 1 < Q2 < 9 (GeV/c)2, 0.2 < z < 0.9 and 0 < PT < 1.3 GeV/c. The principal scientific goal of this experiment is to extract the flavor dependence of the quark polarization, in particular determining their transverse momentum dependence. High precision 5-D (x, z, PT, Q2, φh) data on the neutron, in a kinematic region inaccessible and complementary to the EIC, will constrain present theoretical ideas of the spin structure of the nucleon described by QCD. In combination with measurement on the Deuteron target, this data will also offer an unprecedented opportunity to study the spin-dependent in-medium hadronization process. |
Wednesday, October 13, 2021 3:12PM - 3:24PM |
LF.00007: The polarization sensitivity of GRETINA Chris Morse Characterization of the spins and parities of nuclear states, including excited states, is fundamental to nuclear structure physics. Direct measurement of these quantities can be achieved through Compton polarimetry, which exploits the sensitivity of the Compton-scattering cross section to the polarization state of incident photons. Historically, such studies have been conducted with dedicated experimental setups using multiple detectors in specific geometries which offer high sensitivity, but very limited efficiency. In contrast, γ-ray tracking arrays, such as the Gamma Ray Energy Tracking In-beam Nuclear Array (GRETINA), provide sensitivity to the Compton scattering angles throughout their active volumes, thereby achieving both high polarization sensitivity and high γ-ray detection efficiency simultaneously. Using the well-studied reaction 24Mg(p,p'γ), which produces highly linearly-polarized γ rays, we have performed an experiment to characterize GRETINA as a Compton polarimeter. The analysis of the data and resulting performance of the array will be discussed. |
Wednesday, October 13, 2021 3:24PM - 3:36PM |
LF.00008: Background Simulations with Transversely Polarized Target in CLAS12 Detector Zachary Meador, Latifa Elouadrhiri, David Heddle The CEBAF Large Acceptance Spectrometer (CLAS12) at Jefferson Lab with a dynamically transverse polarized NH3 target is a unique facility to perform the first measurement of transverse target spin asymmetries in deeply inelastic exclusive and semi-inclusive processes over a large kinematical range. The operating luminosity is limited by the electromagnetic background leading to high occupancies in the first 12 layers (Region 1) of the CLAS12 drift chambers system. In this talk we present detailed description of the experiment configuration and the simulation studies to optimize the CLAS12 operation with a transversely polarized target at maximum luminosity. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700