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 K11: Spin Physics and Hard Scattering ProcessesLive Mini-Symposium
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Sponsoring Units: DNP Chair: Kent Paschke, University of Virginia |
Sunday, April 18, 2021 1:30PM - 2:06PM Live |
K11.00001: Overview of nucleon spin structure Invited Speaker: Sanghwa Park Understanding the spin structure of the nucleon in terms of its constituents is one of the most intriguing quests in nuclear physics. The nucleons are a complex and dynamics system of quarks and gluons. Over time, it became evident that one needs to go beyond the collinear description and use the multi-dimensional imaging in order to fully understand the origin of the nucleon spin and its structure. It lead to many experimental efforts and advanced theoretical developments. In this talk, I will present an overview of the recent progress in nucleon spin structure studies. [Preview Abstract] |
Sunday, April 18, 2021 2:06PM - 2:18PM Live |
K11.00002: Twist-three Generalized Parton Distributions and Transverse Angular Momentum Sum Rules Yuxun Guo, Xiangdong Ji, Kyle Shiells We survey and report our analysis on the leading and subleading generalized parton distributions (GPDs) relevant to the nucleon's internal spin structure. We construct both covariant and partonic spin sum rules for the cases of both a longitudinally and transversely polarized nucleon in terms of twist-2 and twist-3 (generalized) parton distribution functions, connecting them to previous results in the literature. In particular, we found a new twist-3 sum rule for the transverse spin which involves the well-know spin structure function $g_T(x)$, and transverse gluon polarization density $\Delta G_T(x)$, and some novel twist-3 GPDs. [Preview Abstract] |
Sunday, April 18, 2021 2:18PM - 2:30PM Live |
K11.00003: Extracting twist three GPDs from deeply virtual compton scattering Kyle Shiells, Xiangdong Ji, YUXUN GUO Observables in the hard exclusive leptoproduction of real photons can be cleanly expressed in terms of the compton amplitudes involving generalized parton distributions (GPDs). This process can be factorized into the product of a short-distance partonic subprocess with a long-distance, off forward hadronic matrix element. They involve nonlocal quark and gluon operators and are naturally expressed in terms of GPDs; quantities which may carry crucial information about the nucleon's intrinsic angular momentum. In this talk, I will be providing an overview of the theoretical formalisms of these processes and a detailed look at some of the relevant asymmetry observables is given to twist-three accuracy. In particular, the relevant twist-two and -three GPDs which complete a newly-found nucleon spin sum rule in the transverse polarization plane are discussed. [Preview Abstract] |
Sunday, April 18, 2021 2:30PM - 2:42PM Live |
K11.00004: Measurement of Mid-rapidity Inclusive Jet Cross Section in $pp$ Collisions at $\sqrt{s} = 200$ GeV Dmitry Kalinkin Jets provide one of the primary tools to study the partons inside protons. The cross section of inclusive jet production is one of the main observables to study the hard scattering. It is well described by pQCD in the collinear factorization framework. For proton-proton collisions at RHIC at a center-of-mass energy $\sqrt{s} = 200~\text{GeV}$, the STAR detector provides measurements at $x_T \equiv \frac{2p_T}{\sqrt{s}}$ as high as $\sim 0.4$. At this energy and in this kinematic region, the direct scattering on gluons inside the colliding protons contributes about a half of the total cross section. Thus, measuring the inclusive jet cross section at RHIC, together with the past Deep Inelastic Scattering measurements, can provide further constraints on the gluon Parton Distribution Function at high $x$. The status report for a new measurement of inclusive jet cross section at mid-rapidity at STAR using the $\sqrt{s} = 200~\text{GeV}$ $pp$ data from 2012 will be presented. Compared to the previous measurement from 2006, improvements include: employing the anti-$k_T$ jet reconstruction, a full barrel and endcap electromagnetic calorimeter acceptance, unfolding of the detector response, and correcting jet parameters for underlying event [Preview Abstract] |
Sunday, April 18, 2021 2:42PM - 2:54PM Live |
K11.00005: Exploring the Spin Structure of the Neutron by the Measurement of g$_2$ and d$_2$ Murchhana Roy, Wolfgang Korsch The experiment E12-06-121 at Jefferson Lab aims to do a precision measurement of the neutron spin structure function g$_2$ using the inelastic scattering of electrons over the kinematic range 0.20 $<$ x$_{Bj} <$ 0.95 and 2.5 $<$ Q$^{2} <$ 6.0 (GeV/c)$^2$. The large kinematic coverage will allow for the precision determination of d$_2$, the third moment of the linear combination of the spin structure functions g$_1$ and g$_2$. As one of the cleanest higher twist observables, g$_2$ contains information on quark-gluon correlations, and d$_2$ is connected to the ``color polarizability" of the nucleon. The experiment was performed and successfully completed in Hall C using a longitudinally polarized 10.4 GeV electron beam and a polarized helium-3 gas target. The combination of Super High Momentum Spectrometer (SHMS) and High Momentum Spectrometer (HMS) allowed us to run the experiment for three constant Q$^2$ values over a wide range of x$_{Bj}$ for the first time. The extraction of d$_2^n$(Q$^2$) will serve as a benchmark to the predictions from Lattice QCD. An overview of the experiment and the present status of the experimental data analysis will be presented. [Preview Abstract] |
Sunday, April 18, 2021 2:54PM - 3:06PM Live |
K11.00006: Probing the sea with Kaon SIDIS Fatiha Benmokhtar Precise evaluation of the sea contribution to the proton spin is of a big importance in the understanding of the dynamics inside the nuclear matter. In particular, the strange sea is an unsolved puzzle and needs a proper experimental attention. To this end, the E12-09007 experiment in CLAS12 of Hall B at Jefferson lab will run electron beams on both polarized and unpolarized hydrogen and deuterium targets and will cover the x-range from 0.05 to 0.7. As a result, this experiment will measure the x-dependence of the strange parton distribution function (PDF) and will help constrain the global fits used to obtain the fragmentation functions (FF). In addition this data will allow the extraction of the individual contributions of quarks and anti-quarks to the nucleon spin. Part of the unpolarized measurements has been already achieved and preparations for the polarized measurements are underway. The experiment requires the use of a Ring Imaging Cherenkov (RICH) detector for a successful charged kaon identification in the 3 to 8 GeV/c momentum range. One RICH detector is built and is fully unctional while a second one is under construction. [Preview Abstract] |
Sunday, April 18, 2021 3:06PM - 3:18PM Live |
K11.00007: Spin physics Opportunites at the U.S.-Based Electron-Ion Collider Ernst Sichtermann The U.S.-based Electron-Ion Collider will be able to collide polarized electron beams with polarized nucleon beams at high luminosity over a wide kinematic range. This unique capability will make make it possible to perform unprecedented studies of the spin structure of the nucleon in hard scattering processes. This talk will discuss selected opportunities and associated detector requirements. [Preview Abstract] |
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