Bulletin of the American Physical Society
APS April Meeting 2022
Volume 67, Number 6
Saturday–Tuesday, April 9–12, 2022; New York
Session K11: Mini-symposium: Multidimensional Structure of Hadrons IIIMini-Symposium Recordings Available
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Sponsoring Units: DNP Chair: Daniel Pitonyak, Lebanon Valley College Room: Majestic |
Sunday, April 10, 2022 1:30PM - 2:06PM |
K11.00001: On the Model Independent Extraction of Compton Form Factors from Deeply Virtual Compton Scattering Invited Speaker: Kyle L Shiells The deeply virtual Compton scattering process e+p → e+p+γ is a flagship experiment for studying nucleon structure through its dependence on generalized parton distributions. Meanwhile, its cross sections depend directly on an intermediate observable quantity known as Compton form factors (CFFs). I summarize the exercise of locally extracting the real and imaginary parts of the four twist-2 CFFs which arise in this important process. It is found that there are a sufficient number of DVCS observables and degrees of freedom to extract all the twist-2 CFFs model-independently, exploiting the azimuthal dependence of the absolute cross sections across all possible beam and target polarizations at a common kinematical point in {Q,t,xB,y}. To achieve this, re-weighted DVCS cross sections have been used which have also been reduced to their dominant terms, found after averaging them over typical JLab fixed-target kinematics. I demonstrate with both real and pseudo-data how one can extract the twist-2 CFFs using harmonic fitting to both cross sections and asymmetries. This analysis is extended to the twist-3 CFFs as well and the phenomenology of future experimental measurements is discussed. |
Sunday, April 10, 2022 2:06PM - 2:18PM |
K11.00002: High order kinematical effects in DVCS for EIC YUXUN GUO, Xiangdong Ji, Kyle L Shiells We apply the frame-independent deeply virtual Compton scattering cross-section formula to the EIC kinematics and study the high order kinematical effects, including both kinematical higher-twist effects, corrections from higher-twist CFFs and quantum loop corrections to the next-to-leading order of strong coupling. We show how those effects compared with the leading order contribution, which plays an important role in extracting the leading twist Compton form factors with precision. |
Sunday, April 10, 2022 2:18PM - 2:30PM |
K11.00003: Measuring nucleon spin and mass through higher twist generalized parton distributions Simonetta Liuti, Osamah Alkassassbeh, Abha Rajan, Michael Engelhardt Understanding the origin of the proton spin and mass as they emerge from quark and gluon distributions is a central question in QCD and a main quest for current experimental programs worldwide, as well as at the future Electron Ion Collider (EIC). I will present the essential steps of our approach, involving QCD manipulations of the relevant correlations functions using the equations of motion, to obtain the quark longitudinal angular momentum decomposition into its spin and orbital components. The power of this approach is in that it provides a connection between twist three generalized parton distributions (GPDs) and generalized transverse momentum distributions (GTMDs) while conserving gauge invariance, thus revealing the inner workings of quark and gluon transverse momentum components. I will show how transverse angular momentum can also be described, and the twist three GPD that describes the transverse OAM can be identified. I will finally discuss the extension of this approach to the proton mass decomposition. |
Sunday, April 10, 2022 2:30PM - 2:42PM |
K11.00004: Coordinate Space Representation and Average Radius of Quark and Gluon Generalized Parton Distribution Functions Zaki Panjsheeri, Brandon Kriesten, Krisean Allen, Joshua Beethoven P Bautista, Philip Velie, Simonetta Liuti Two-dimensional Fourier transforms of generalized parton distributions (GPDs) provide insight into matter, charge, and radial distributions of the quarks and gluons inside the nucleon. We present an explicit calculation of such transforms in a spectator model framework using parametric analytic forms of GPDs, originally constrained using deeply virtual Compton scattering and lattice QCD data. Calculations were performed for several values of the momentum fraction X and evolved using perturbative QCD from the initial scale Q0 to the scale of the data at 10 GeV. We compare the valence quarks to the gluon distribution through, i.a., average radii, a notion of distance inside the nucleon, and we present a novel result for the radius of the gluon density. We also studied the effect of evolution, the normalization of the Fourier transforms through parton distribution functions in the off-forward limit of the GPDs, and the difference between matter and charge density in both the proton and the neutron. |
Sunday, April 10, 2022 2:42PM - 2:54PM |
K11.00005: Deeply Virtual Compton Scattering Beam-Spin Asymmetry at 6.5 GeV and 7.5 GeV Polarized Electron Beam with CLAS12 Latifa Elouadrhiri, Joshua Artem D Tan, Francois-Xavier Girod Deeply Virtual Compton Scattering (DVCS) is the cleanest channel providing access to the 3D nucleon imaging mapped by Generalized Parton Distributions (GPDs) which correlate the 1D longitudinal momentum fraction of the nucleon’s constituent to its 2D transverse position. In DVCS reaction, the virtual photon from the scattered electron interacts with a quark inside the nucleon, leading to the emission of a high-energy real photon from the nucleon. Detection of DVCS events, however, implies detection of Bethe-Heitler (BH) events, which have the same final-state particles but with the scattered electrons emitting the photons. DVCS measurements at different beam energies allow DVCS amplitude and DVCS-BH interference amplitude’s separation necessary for the extractions of GPD H in some kinematics, and eventually the gravitational form factor, which encodes the mechanical properties of the nucleon. |
Sunday, April 10, 2022 2:54PM - 3:06PM |
K11.00006: Measurement of DVCS Cross Section off Protons with CLAS12 Sangbaek Lee We present a status report on the proton DVCS differential cross-section using the CLAS12 detector at Jefferson Lab. The DVCS process involves deeply inelastic electroproduction of real photons in the scattering from the struck quark inside the proton. The extracted cross-section enables three-dimensional imaging of the proton structure in the framework of GPDs. The experiment utilized a 5 cm long, unpolarized, liquid hydrogen target, the CEBAF 10.6 GeV polarized electron beam, and state-of-the-art particle detectors located in a magnetic field produced by a solenoid and torus, which enabled particle identification and momentum reconstruction. We will also discuss the physical interpretation of the measurement. |
Sunday, April 10, 2022 3:06PM - 3:18PM |
K11.00007: Coherent Deuteron DVCS Analysis to Extract a Beam Spin Asymmetry (ALU) Nicholas G Richardson, Angela Biselli Generalized Parton Distributions (GPDs) offer insight into the internal structure of nucleons, specifically giving an in-depth look into their individual constituents namely quarks and gluons. Deeply Virtual Compton Scattering, is one of the primary ways to access these GPDs. Due to the complex nature of the spin-1 Deuteron, there are theorized to be nine GPDs. To further learn about these GPDs we are studying coherent DVCS on the deuteron (e D → e’ D’ ??) to extract a Beam Spin Asymmetry (BSA) using Pass-1 data from Jefferson Lab’s Run Group B. This run featured a longitudinally polarized beam on an unpolarized deuteron target. In this poster we will present our preliminary analysis to select events with an electron, deuteron, and photon in the final state and the selection process to identify DVCS events via strict kinematic cuts. Additionally, we will present a novel way to verify and identify deuterons using machine learning. Finally, we will show a preliminary BSA for coherent DVCS, which is the first of its kind, giving insight into the GPDs of the deuteron. |
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