Bulletin of the American Physical Society
APS April Meeting 2021
Volume 66, Number 5
Saturday–Tuesday, April 17–20, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session T15: Nucleon Structure and Spin IILive
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Sponsoring Units: GHP Chair: Lamiaa El Fassi, Mississippi State University |
Monday, April 19, 2021 3:45PM - 3:57PM Live |
T15.00001: Measuring the Neutron Spin Asymmetry A$_{\mathrm{1}}^{\mathrm{n}}$ in the Valence Quark Region in Hall C at Jefferson Lab Melanie Rehfuss, 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 (x$_{\mathrm{bj}})$, exist, there remains much to learn about their x$_{\mathrm{bj}}$-dependence. With the breakthrough of the quasi-PDFs formalism, confronting \textit{ab-initio} calculations of unintegrated spin observables including OAM will be possible. The neutron spin asymmetry A$_{\mathrm{1}}^{\mathrm{n}}$ at high x$_{\mathrm{bj}}$ is a key observable for probing nucleon spin structure since in the valence domain (x$_{\mathrm{bj}}$ \textgreater 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. A$_{\mathrm{1}}^{\mathrm{n}}$ was measured in the deep inelastic scattering region of 0.30 \textless x$_{\mathrm{bj}}$ \textless 0.75 and 3 \textless Q$^{\mathrm{2}}$ \textless 10 (GeV/c)$^{\mathrm{2}}$ in Hall C at Jefferson Lab using a 10.4 GeV longitudinally polarized electron beam, upgraded polarized $^{\mathrm{3}}$He target, and the High Momentum Spectrometer (HMS) and Super High Momentum Spectrometer (SHMS). The wide Q$^{\mathrm{2}}$ range will explore possible Q$^{\mathrm{2}}$ dependence on A$_{\mathrm{1}}^{\mathrm{n}}$, provide the first precision data in the valence quark region above x$_{\mathrm{bj}}=$ 0.61, and therefore test various predictions and ultimately \textit{ab-initio} lattice QCD calculations. [Preview Abstract] |
Monday, April 19, 2021 3:57PM - 4:09PM Live |
T15.00002: Comparing Quark Distribution Moments Extracted from Experimental Data to Precision Lattice QCD Calculations Peter Monaghan Thanks to advances in Lattice QCD (LQCD), calculations of the moments of quark flavor Parton Distribution Function (PDF) combinations are now available. These precision calculations can be compared to quark distribution moments extracted from experimental data, specifically using the difference between the proton and neutron $F_{2}$ structure function moments. Details of the analysis and the resulting comparison with numerous different LQCD calculations will be presented. This work is supported in part by NSF grant PHY-1812369. [Preview Abstract] |
Monday, April 19, 2021 4:09PM - 4:21PM Live |
T15.00003: Generalized Parton Distributions with Timelike Compton Scattering Camille Zindy, Marie Boer Hard exclusive processes such as photoproduction or electroproduction of photon or meson off the nucleon provide access to the Generalized Parton Distributions (GPDs). These functions contain the correlation between the longitudinal momentum fraction and the transverse spatial densities of quarks and gluons in the nucleon. Timelike Compton Scattering (TCS) corresponds to the reaction $\gamma P \to \gamma^* P'\to e^+e^-P'$, where the virtual photon is scattered off a quark. Comparison of GPDs extracted from TCS and DVCS, its spacelike equivalent, is very important as it will allow for studying GPD's universality. We performed data analysis based on TCS simulations to develop future experiments at JLab. We will present the results of our studies. [Preview Abstract] |
Monday, April 19, 2021 4:21PM - 4:33PM Live |
T15.00004: Theoretical and Phenomenological Understanding of Quark-hadron Duality Huma Haider, Mary Hall Reno Quark-hadron duality connects the resonance and deep inelastic scattering (DIS) region in the intermediate energy regime of electron-proton ($ep$) scattering. Resonances include the $\Delta(1232)$ and other heavier nucleon resonances peaking at higher hadron invariant mass $W$ ($\sim 1.4-2.0$ GeV), a kinematic region which needs study to better understand the transition between a hadronic resonance description and a perturbative QCD description of $ep$ inelastic scattering. We present results for the structure function $F_2(x,Q^2)$ and $F_1(x,Q^2)$ for electron-proton inelastic scattering including nonperturbative and higher order perturbative QCD effects. With theoretically motivated extrapolations to low momentum transfers, we compare our results with parametrized structure functions and JLAB data for inclusive $ep$ scattering. A better understanding of quark-hadron duality in $ep$ scattering will have implications for neutrino-nucleon/nucleus scattering, important for the neutrino experiments like NO$\nu$A, MINER$\nu$A and DUNE which have significant numbers of events in this less explored transition region. [Preview Abstract] |
Monday, April 19, 2021 4:33PM - 4:45PM Live |
T15.00005: The BONuS Experiment with CLAS12 Mohammad Hattawy, Sebastian Kuhn The BONuS experiment studies nearly free neutrons through electron scattering observables like structure functions, Deeply Virtual Compton Scattering (DVCS), and other reactions. By observing a slow, backwards-moving spectator proton in the reaction D($e,e^\prime p_s$)X in coincidence with the scattered electron and other reaction products, nuclear uncertainties are minimized. BONuS collected data in winter and summer 2020 in Hall B of Jefferson Lab with an electron beam of 10.4 GeV, using the CLAS12 spectrometer and a custom-built, state-of-the-art Radial Time Projection Chamber (RTPC). In this talk, we will discuss the performance of the RTPC, and present the status of the data analysis. [Preview Abstract] |
Monday, April 19, 2021 4:45PM - 4:57PM Live |
T15.00006: GPU Online Reconstruction for J/Psi TSSA Study at SpinQuest Catherine Ayuso h $-abstract-$\backslash $pardThe E1039/SpinQuest experiment is a transversely polarized fixed target experiment at Fermi National Accelerator Laboratory aiming to explore the sea quark and gluon Sivers functions via the measurement of the transverse single spin asymmetry (TSSA) for a number of physics processes including J/Psi, Psi' and Drell-Yan production. The experiment employs a 120-GeV extracted proton beam colliding with transversely-polarized NH3 and ND3 cryogenic targets and its spectrometer is optimized to detect the oppositely-charged muon pair output of these processes. In pursuit of these asymmetry measurements, we are seeking to develop an advanced GPU-based multi-threaded framework that allows an efficient parallelization of the online data processing, which will facilitate prompt online reconstruction, optimization, and robust data quality monitoring. In this talk, I will report the status of our GPU online reconstruction project along with results estimating the anticipated accuracy of the TSSA measurement via J/Psi production from early SpinQuest production data.$\backslash $pard-/abstract-$\backslash $\tex [Preview Abstract] |
Monday, April 19, 2021 4:57PM - 5:09PM Live |
T15.00007: Analysis Status of The Measurement of Charm and Bottom Production in PHENIX Zhiyan Wang It has long been observed experimentally, from previous heavy-flavor electron measurements, that heavy quarks are subject to substantial modifications of their momentum spectrum. The PHENIX Collaboration at the Relativistic Heavy Ion Collider (RHIC) has measured open heavy-flavor production in minimum bias p+p and Au+Au collisions at $\sqrt[]{S_{NN}}$ = 200 GeV, by measuring the different decay lengths using a silicon vertex detector. The comparisons between Au+Au and p+p collisions shed light on properties of hot nuclear matter, as well as quark-gluon plasma's influence on the heavy-flavor electron's nuclear modification factor $R_{AA}$. In our analysis, p+Au collisions at $\sqrt[]{S_{NN}}$ = 200 GeV are studied, and provide another contributing factor to heavy-ion collision as the cold nuclear matter baseline. The status of the analysis will be presented including data quality assurance, recalibration and electron identification, production of inclusive electrons' DCA distribution measured by VTX, as well as simulation of the DCA distributions of electron backgrounds. [Preview Abstract] |
Monday, April 19, 2021 5:09PM - 5:21PM Live |
T15.00008: Isospin amplitudes in b-baryon decays Aravindhan Venkateswaran Ratios of isospin amplitudes in hadron decays are a useful probe of the interplay between weak and strong interactions, and allow searches for physics beyond the Standard Model. We present the first results on isospin amplitudes in $b$-baryon decays, using data corresponding to an integrated luminosity of $8.5 \mathrm{fb}^{-1}$, collected with the LHCb detector in $pp$ collisions at center of mass energies of 7, 8 and 13 TeV. The isospin amplitude ratio $|A_1(\Lambda_b \rightarrow J/\psi \Sigma^0)/A_0(\Lambda_b \rightarrow J/\psi \Lambda)|$, where the subscript on $A$ indicates the final-state isospin, is measured to be less than $1/21.8 $ at 95\% confidence level. This upper limit provides support for the light diquark structure in the $\Lambda_b$, and further confirms its SM status as an isosinglet. The Cabibbo suppressed $\Xi_b^0 \rightarrow J/\psi \Lambda$ decay is observed for the first time, allowing for the measurement $|A_0(\Xi_b^0 \rightarrow J/\psi \Lambda)/A_{1/2}(\Xi_b^0 \rightarrow J/\psi \Xi^0)| =0.37 \pm 0.06 \pm 0.02$, where the uncertainties are statistical and systematic, respectively. This measurement is consistent with the preservation of both isospin and SU(3) flavor symmetries. [Preview Abstract] |
Monday, April 19, 2021 5:21PM - 5:33PM Live |
T15.00009: Interests and opportunities to measure Double Deeply Virtual Compton Scattering Marie Boer The so-called Generalized Parton Distributions (GPDs), containing information about the parton's longitudinal momenta and their transverse position, can be accessed through hard exclusive processes. Double Deeply Virtual Compton Scattering (DDVCS), corresponding to the scattering of a virtual photon off a quark followed by the emission of a photon of different virtuality, is a "golden channel" to study GPDs. Indeed, as for DVCS or TCS (Spacelike and Timelike Deeply Virtual Compton Scattering) it only involves one non-pertubative QCD part, corresponding to GPDs, while other parts can be calculated. In addition, the relative virtuality of the 2 photons provides a lever arm to vary the kinematic points at which we access GPDs, bringing new constrains for tomographic interpretations of the GPDs. We will discuss the interest of measuring DDVCS and some new opportunities at Jefferson Lab. [Preview Abstract] |
Monday, April 19, 2021 5:33PM - 5:45PM Live |
T15.00010: GHP Dissertation Award (2021): A High Precision Measurement of the Proton Charge Radius at JLab1 Weizhi Xiong In 2010, a new method using muonic hydrogen spectroscopy led to a pro- ton charge radius (rp) result that was nearly ten times more precise but significantly smaller than results obtained using the two traditional meth- ods, namely e − p scattering and ordinary Hydrogen spectroscopy. This discrepancy triggered the so-called “proton charge radius puzzle”. To inves- tigate this discrepancy, the PRad collaboration performed a new experiment in 2016 in Hall B at the Thomas Jefferson National Accelerator Facility. With both 1.1 and 2.2 GeV electron beams, the experiment measured the e − p elastic scattering cross sections in an unprecedentedly low values of momentum transfer squared region (Q2 = 2.1 × 10−4 − 0.06 (GeV/c)2 ), with a sub-percent precision. The PRad experiment utilized a magnetic- spectrometer-free setup, which was based on a large acceptance and high resolution calorimeter (HyCal), a plane of two large-area Gas Electron Mul- tiplier (GEM) detectors, and a windowless H2 gas-flow target. In this talk, I will discuss details of the data analysis and present the results of this experi- ment. I will also discuss briefly the PRad-II experiment, which will improve the uncertainty of rp by a factor of ∼4 compared to that of PRad. [Preview Abstract] |
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