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 QK: Hadron Structure II |
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Chair: Astrid Hiller Blin, JLab Room: Arlington |
Thursday, October 14, 2021 11:30AM - 11:42AM |
QK.00001: Charged-pion multiplicity ratio and EMC effect in e-A DIS with CLAS sebastian i moran We present a measurement of charged-pion production in DIS off 2H, C, Fe, and Pb using the CLAS detector and the CEBAF 5 GeV electron beam. We report a triple-differential measurement of the multiplicity ratio for pi+ and pi- as a function of virtual-photon energy and virtuality, and pion momentum fraction or transverse momentum. The results are compared with the GiBUU transport model, nuclear fragmentation functions, as well as with a model based on pre-hadron absorption. Also, we report results for the EMC ratio that extends previous measurements to lower Q2 and compare with expectations from nuclear PDFs. These precise results could help constrain the flavor dependence of nuclear effects and probe an unexplored kinematic region where the hadronization timescales are expected to be of the same order as the nuclear lengths. |
Thursday, October 14, 2021 11:42AM - 11:54AM |
QK.00002: Examining the EMC effect using the F2n neutron structure function Narbe Kalantarians Using electron scattering data from SLAC E139 and muon scattering data from NMC in the DIS region, we determine the F2A/F2p and F2A/F2n structure function ratios, spanning 0.3 < x < 0.8 and 1 < Q2 < 200 GeV/c This region is of particular relevance to studies of the EMC Effect. The structure of the free proton is well known from numerous experiments, but the free neutron structure function has remained difficult to access. Recently, the free neutron structure function has been extracted in a systematic study of the global data within a parton distribution function extraction framework and is available from the CTEQ-Jefferson Lab (CJ) Collaboration. In this talk, we leverage the recent global free neutron extraction to introduce a new method to study the EMC Effect in nuclei by re-examining existing data and by now determining the magnitude of the medium modifications to the free neutron and proton structure functions, independently. We further examine the nuclear effects in deuterium and their contribution to our interpretation of the EMC Effect. This talk will summarize the results of the mentioned ratios for the SLAC E139 nuclei using the F2n global data from the CJ Collaboration. |
Thursday, October 14, 2021 11:54AM - 12:06PM |
QK.00003: Nucleon off-shell structure and the free neutron valence structure from A=3 inclusive electron scattering measurements Efrain P Segarra, Jackson R Pybus, Tyler T Kutz, Douglas W Higinbotham, Gerald A Miller, Eli Piasetzky, Axel W Schmidt, Mark Strikman, Lawrence B Weinstein, Or Hen, Florian Hauenstein Understanding the differences between the distribution of quarks bound in protons and neutrons is key for constraining the mechanisms of SU(6) spin-flavor symmetry breaking in Quantum Chromodynamics (QCD). The recent MARATHON experiment attempted to extract neutron structure with reduced model dependence by comparing scattering from He-3 and tritium, isospin mirror nuclei. |
Thursday, October 14, 2021 12:06PM - 12:18PM |
QK.00004: Short Range Quark-Quark Interactions and Nucleon Structure Function at High Bjorken x Joseph E Maerovitz, Misak M Sargsian, Christopher A Leon We investigate the role of the quark-quark interaction at shortdistances in the generation of the strength of nucleon structure function at high Bjorken x. This work represents the continuation of our previous study, in which we developed a residual mean field model of nucleon structure function. The parameters of the mean-field model obtained in description of the valence PDFs at 0.1 < x< 0.5 is used to describe the non- perturbative part of the structure function while hard gluon exchanges are introduced to calculate the strength of the high x part of the same structure function at x>0.5. In the calculation we considered both two- and three-quark short range interactions through hard gluon exchange which arecalculated within perturbative QCD. |
Thursday, October 14, 2021 12:18PM - 12:30PM |
QK.00005: Using Python to Curve Fit Tensor Polarized Deuteron Signals Michael J McClellan Dynamic nuclear polarization (DNP) is a necessary tool for certain experiments, such as the measurement of Azz and b1, and the polarization of such targets can be measured via nuclear magnetic resonance (NMR). The NMR signal of a proton is a simple Lorentzian, but a deuteron signal is more complex, having two overlapping peaked functions, due to the deuteron being a spin-1 particle. In materials, such as ND3, where the peaks are not fully superimposed, it is not just the vector polarization (Pz) that can be measured, being a pure scaling of the signal from an unenhanced thermal equilibrium (TE) signal, but also the tensor polarization (Pzz), which is a measure of the difference between the two component signals. This is even further complicated in materials, such as d-propanediol, with different types of deuteron bonds, creating multiple pairs of peaks in the signal. Ideally, this total signal would be compared to a TE signal to calculate Pzz in a similar manner to Pz, but deuteron TE signals are very small and difficult to distinguish from noise. I have thus developed a Python macro to fit a raw polarized deuteron signal to the functional form laid out by Dulya et al. The resultant fitted functions match the data with a standard deviation of less than 1%, and Pzz is able to be derived from them, but so far they do not match Pzz as calculated via TE methods. In future, I will also need to amend Dulya et al.'s function to account for hole-burning techniques to increase tensor polarization. |
Thursday, October 14, 2021 12:30PM - 12:42PM |
QK.00006: NRQCD matching calculations aided by the threshold expansion Reed Hodges, Thomas C Mehen The computation of matching coefficients is one of the most crucial elements of effective field theory. It allows one to write down operators for a Lagrangian that is a good low-energy approximation to the Standard Model. Typical matching calculations involve studying a scattering process in the full theory and the effective theory, and tuning the Wilson coefficients so that the amplitudes match in the energy domain of interest. Here we present a simpler method for computing matching coefficients in Non-Relativistic Quantum Chromodynamics (NRQCD) that bypasses the need to compute amplitudes in full QCD. We expand a full QCD diagram in the threshold expansion of Beneke & Smirnov [1] and identify the expanded integrals directly with NRQCD integrals. The NRQCD amplitudes then can be immediately cancelled out, leaving only the matching contributions. We test this procedure against previous results for the heavy quark-quark potential at one loop. |
Thursday, October 14, 2021 12:42PM - 12:54PM |
QK.00007: Investigations on the Coulomb flux tube Wyatt A Smith, Sebastian M Dawid, Adam P Szczepaniak SU(N) Coulomb gauge Lattice QCD provides an effective way to probe aspects of quark confinement. It allows investigation of the effect of the instantaneous color Coulomb interaction on the energy density profile between static quark-antiquark pairs. Recent works have computed the Coulomb flux tube profile and compared it to the Wilsonian flux tube to distinguish between collimated and dipole-like behavior. However, these results were not definitive. We will present our attempts to continue these calculations on larger lattice volumes. Due to the instantaneous nature of the Coulomb interaction, Coulomb gauge observables are defined in the limit where their time extent vanishes. We also discuss the time evolution of the coulomb flux tube as well as extrapolation of the limit β→∞ on anisotropic lattices to gain insight into this T→0 limit. |
Thursday, October 14, 2021 12:54PM - 1:06PM |
QK.00008: A novel machine learning approach for CLAS12 first-pass track estimation Audrey Lawton, David P Heddle The reconstruction of CLAS12 data begins with the invocation of an algorithm named SNR. SNR finds and removes uncorrelated drift chamber hits or "noise". A by-product of the algorithm is a series of extended (128 bit) words with bits set at sense wire locations corresponding to track segment candidates. Presently this segment data is discarded, and reconstruction continues in a traditional manner using the drift chamber data as cleaned by SNR but ignoring the resultant SNR segment candidates. In this work we investigate using the SNR track segment data as input for a machine learning algorithm, where the output is an estimate of the track parameters, i.e., the charge, vertex, momentum, and direction for each track. |
Thursday, October 14, 2021 1:06PM - 1:18PM |
QK.00009: Track identification in Phase II of Project 8 with machine learning techniques Yu-Hao Sun Project 8 is a direct neutrino mass experiment using the tritium endpoint method. To achieve the sensitivity goal of 40 meV, the Project 8 collaboration has developed the technique of Cyclotron Radiation Emission Spectroscopy (CRES) to measure the energy of a beta electron from the frequency of its cyclotron radiation in a magnetic field. In Phase II of Project 8, the electron signals show up as tracks on top of the noise background in spectrograms. In this talk, I will present our progress in using machine learning methods to extract electron signals from the noise background in simulated Phase II data. |
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