Bulletin of the American Physical Society
Four Corners Section 2022 Meeting
Volume 67, Number 14
Friday–Saturday, October 14–15, 2022; Albuquerque, New Mexico
Session E01: Nuclear/Particle Physics I |
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Chair: Dinesh Loomba, University of New Mexico Room: UNM PAIS 1100 |
Friday, October 14, 2022 2:30PM - 2:54PM |
E01.00001: The Coulomb Sum Rule in Nuclei Invited Speaker: Michael E Paolone Since the discovery of the EMC effect, where it was observed that the quark longitudinal momentum distributions in a nucleus are different from those of free nucleons, there has been a long standing question in nuclear physics as to how the structure of a free nucleon might change when bound in a nucleus or embedded in a nuclear medium. One of the cleanest expected signatures of in-medium modification can be achieved by testing the Coulomb Sum Rule through quasi-elastic electron scattering; where one counts the expected total nuclear charge by integrating the longitudinal response function of the nucleus and comparing it to the incoherent sum of electric form factors of the constituent nucleons. Standard nuclear effects that quench the charge response of the nucleus are well understood, leaving any additional quenching to be interpreted as a signature of modification of these form factors in-medium. Preliminary results from a recent analysis of inclusive electron scattering from Carbon and Iron targets at Jefferson Lab will be presented. |
Friday, October 14, 2022 2:54PM - 3:06PM |
E01.00002: Parton Helicity Evolution at Small-x Nicholas Baldonado, Matthew D Sievert, Yuri V Kovchegov, Daniel M Adamiak, Andrey Tarasov, Daniel Pitonyak, Yossathorn Tawabutr, Nobuo Sato, Wally Melnitchouk The proton is well known to be a spin-1/2 particle, however current experimental measurements of the quark and gluon spins do not add up to 1/2. Experiments can only provide data up to the energy limit of their colliders, but our theoretical approach can extrapolate the helicity of quarks and gluons to arbitrarily small-x (arbitrarily high energy). In this talk I will discuss how we use a polarized dipole formulation of DIS and SIDIS to predict the small-x (high-energy) asymptotics of quark and gluon helicity. Our method defines spin related observables, such as the helicity parton distribution functions (hPDFs), using a set a of polarized dipole amplitudes. We then construct and solve the evolution equations of these polarized dipoles to describe their behaviour at small-x, and apply their small-x asymptotics to the hPDFs. In this way we can use theory to predict how much spin resides inside the proton in regions beyond current experimental possibilities. Using a combination of numerical and analytic solutions, our theory predicts that at small-x the quark and gluon hPDFs, ΔΣ and ΔG, grow with the power scaling ΔΣ ∼ ΔG ∼ (1/x)3.66 √(αsNc/2π) implying that a potentially large amount of the proton spin may be hidden in this small-x region. Our current focus is to further optimize our theoretical and numerical representation of this formalism, and to perform a global analysis of inclusive DIS at small-x using the latest refinements. |
Friday, October 14, 2022 3:06PM - 3:18PM |
E01.00003: Modeling Longitudinal Energy Deposition in Relativistic Heavy Ion Collisions Ryan Hamilton Relativistic collisions of heavy nuclei produce small droplets of quark-gluon plasma. In order to extract plasma properties, one needs a model for the initial energy deposition both along the beam direction (longitudinal) and perpendicular to that (transverse). In Ref. [Phys. Rev. C 102, 014909], the longitudinal energy deposition is calculated via nuclear thickness functions. We have written code to reproduce this modeling, and also propose a new calculation making a very different set of assumptions: i.e., that the energy deposit follows a color-string type picture. In this talk we present results from both models at different A+A impact parameters and collisions energies. Such results include longitudinal energy distributions, pseudorapidity-dependent transverse energy distributions, and eccentricity coefficient distributions. |
Friday, October 14, 2022 3:18PM - 3:30PM |
E01.00004: Jet Drift from Collective Flow in Event-By-Event Heavy-Ion Collisions Matthew D Sievert, Joseph Bahder Using a recently-derived theoretical framework to describe the coupling of jets to the velocity distribution in a nuclear medium, we consider the implications for photon-jet acoplanarities in heavy-ion collisions. For a jet propagating in a large uniform slab of plasma, we find that the jet is deflected towards alignment parallel to the direction of the velocity, with the magnitude and direction of the jet deflection carrying significant information about the velocity field. We show that the pattern of angular deflection carries sufficient information to reconstruct both the direction and the magnitude of the velocity. In addition, we find that the time dependence of the deflection along the jet trajectory is also sensitive to the magnitude of the velocity. When applied to the elliptical geometries produced in non-central heavy-ion collisions, this leads to a strong coupling of the photon-jet acoplanarity to the elliptic flow of the plasma itself, and we propose measurements at sPHENIX / LHC which may be able to confirm these predictions. |
Friday, October 14, 2022 3:30PM - 3:42PM |
E01.00005: Real-time Machine Learning classifier to identify long-lived particles at the Large Hadron Collider. Olivia Courtney The Large Hadron Collider at CERN provides the highest-ever proton-proton particle collisions achieved in the laboratory. A major goal of the LHC is to discover physics beyond the Standard Model. This work contributes to an upgrade of the hardware-based data acquisition system for the CMS experiment aimed at detecting new long-lived particles. In contribution to the effort to properly reconstruct particles displaced from the proton-proton collision point, a machine learning classifier was developed to distinguish signal particles that are correctly reconstructed with displacement from background particles that originate from the collision point but are incorrectly reconstructed as displaced. A boosted decision tree was used to classify the quality of displaced particle reconstruction, and in-depth investigation into the characteristics of these tracks was used to optimize the classifier. |
Friday, October 14, 2022 3:42PM - 3:54PM |
E01.00006: Measurement of the Transverse and Longitudinal Diffusion of Ionization Electrons in Liquid Argon with the ICARUS Detector Sebastian B Ruterbories Neutrino experiments using liquid argon time projection chambers (LArTPCs) have shown that the smearing of ionization signal waveforms by diffusion can have a significant impact on particle identification and energy reconstruction. Understanding and accounting for diffusion effects can improve the accuracy and precision of measurements in these detectors. Previous measurements have been made for the longitudinal diffusion constant in liquid argon near a drift electric field of 500 V/cm, where many LArTPC neutrino experiments operate. However, no measurements of transverse diffusion in liquid argon have been made at similar drift electric field values. We present a novel method making use of the relative change in ionization signal waveforms between near-anode and near-cathode data collected using a LArTPC, allowing for the longitudinal and transverse diffusion constants to be measured simultaneously and precisely. First studies using Monte Carlo simulation and data collected with the ICARUS detector, operating at a drift electric field of 493.8 V/cm, are presented. Notably, our measurement of the transverse diffusion constant in liquid argon at ICARUS is the first of its kind near this value of drift electric field. |
Friday, October 14, 2022 3:54PM - 4:06PM |
E01.00007: Conversion of Dark Matter to Light in Multilayer Dielectric Haloscopes Anson L Kost, Ken Van Tilburg The aim of optical halosopes is to detect dark matter particles in the local galactic halo by converting them to Standard Model photons. They are at the forefront of the current effort to directly detect bosonic cold dark matter that behaves like a classical field and may pervade the space around Earth. |
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