Wed·Mar 6, 2024Wednesday·March 6, 2024

1. 01*

   Future measurements of TCS at JLab Hall C

   Debaditya Biswas🇺🇸 · Marie Boër🇺🇸

   Generalized parton Distributions (GPDs) are important functions to understand the three dimensional structure of the nucleon. Deeply Virtual Compton Scattering is one of the reaction accessing GPDs, and has been measured for the past $\sim$20 years. However, to move forward, we need to look for other reactions, such as Timelike Compton Scattering (TCS), its "time-reversal" equivalent. Indeed, accessing GPDs from both DVCS and TCS independently will allow us, for instance, to study their universality. Any assesment on GPD's universality would be a milestone in our field. In this article we discuss our preliminary studies on the feasibility of measuring unpolarized and beam polarized cross sections and beam spin asymmetry for TCS in the dilepton photoproduction reaction. For that purpose, we use a polarized photon beam and an unpolarized target at JLab Hall C. We will discuss our Geant4 simulations, with a dedicated detector setup along with the use of the SBS magnet for separating outgoing $e^{+}$, $e^{-}$ pairs.

   nucl-exPoS(2024)·0 citations
2. 02*

   Double Deeply Virtual Compton Scattering at Jefferson Lab Hall A

   Marie Boër🇺🇸 · Debaditya Biswas🇺🇸

   This paper presents our project and perspectives to measure for the first time beam spin asymmetries from Double Deeply Virtual Compton Scattering in the $eP\to e^{\prime }{P}^{\prime }{\mu }^{+}{\mu }^{-}$ reaction at Jefferson Lab. Our goal is to constrain the so-called Generalized Parton Distribution (GPDs) in a kinematic region that isn't accessible from other reactions, such as Deeply Virtual Compton Scattering, to allow for their extrapolation to "zero skewness", i.e. at a specific kinematic point enabling for tomographic interpretations of the nucleon's partonic structure. We are discussing DDVCS phenomenology and our approach, as well as our experimental project aimed at complementing the SoLID experiment at JLab Hall A with a new muon detector.

   nucl-exhep-phPoS(2024)·1 citation
3. 03*

   Macroscopic neutrinoless double beta decay: long range quantum coherence

   Gordon Baym🇺🇸 · Jen-Chieh Peng🇺🇸

   We re-introduce, in light of our modern understanding of neutrinos, the concept of ``macroscopic neutrinoless double beta decay" (MDBD) for Majorana neutrinos. In this process an antineutrino produced by a nucleus undergoing beta decay, $X\to Y+e^{-}+{\bar{\nu }}_e$, is absorbed as a neutrino by another identical $X$ nucleus via the inverse beta decay reaction, ${\nu }_e+X\to e^{-}+Y$. The distinct signature of MDBD is that the total kinetic energy of the two electrons equals twice the endpoint energy of single beta decay. The amplitude for MDBD, a coherent sum over the contribution of different mass states of the intermediate neutrinos, reflects quantum coherence over macroscopic distances, and is a new macroscopic quantum effect. We evaluate the rate of MDBD for a macroscopic sample of ``$X$" material, e.g., tritium, acting both as the source and the target. The accidental background for MDBD originating from two separate single beta decays, which contains two final state neutrinos, can be readily rejected by measuring the energy of the detected two electrons. We discuss the similarities and differences between the MDBD and conventional neutrinoless double beta decay.

   ↳ nucl-thhep-exhep-phnucl-exNPB(2025)·1 citation
4. 04*

   Examination of STAR fixed-target data on directed flow at $\sqrt{s_{NN}}=$ 3 and 4.5 GeV

   Yu. B. Ivanov🇷🇺 · M. Kozhevnikova🇷🇺

   We present results of simulations of directed flow of various hadrons in Au+Au collisions at collision energies of $\sqrt{s_{NN}}=$ 3 and 4.5 GeV. Simulations are performed within the model three-fluid dynamics (3FD) and the event simulator based on it (THESEUS). The results are compared with recent STAR data. The directed flows of various particles provide information on dynamics in various parts and at various stages of the colliding system depending on the particle. However, the information on the equation of state is not always directly accessible because of strong influence of the afterburner stage or insufficient equilibration of the matter. It is found that the crossover scenario gives the best overall description of the data. This crossover EoS is soft in the hadronic phase. The transition into QGP in Au+Au collisions occurs at collision energies between 3 and 4.5 GeV, at baryon densities $n_B\ge 4n_0$ and temperatures $\approx 150$ MeV. In-medium effects in the directed flow of (anti)kaons are discussed.

   ↳ nucl-thhep-phnucl-exPRC(2024)·6 citations
5. 05*

   Translationally invariant shell model calculation of the quasielastic $(p,2p)$ process at intermediate relativistic energies

   A.B. Larionov🇷🇺 · Yu.N. Uzikov🇷🇺

   Relativistic beams of heavy ions interacting with various nuclear targets allow to study a broad range of problems starting from nuclear equation of state to the traditional nuclear structure. Some questions which were impossible to answer heretofore -- can be addressed nowadays by using inverse kinematics. These includes the structure of short-lived nuclei and the precision study of exclusive channels with production of residual nuclei in certain quantum states. Theoretical understanding such processes is so far based on factorization models which combine the single-step amplitude of the reaction on a bound nucleon or nuclear cluster with a certain wave function of its relative motion with respect to the residual nucleus. The nuclear structure information is encoded in the spectroscopic amplitude, calculable within nuclear many-body theories. In this work, we use for this purpose the translationally-invariant shell model with configuration mixing and demonstrate that it successfully reproduces the single-differential and integrated cross sections of the quasielastic proton knockout, ${}^{12}\text{mbox}C(p,2p{)}^{11}\text{mbox}B$, with outgoing ${}^{11}$B in the ground state and low-lying excited states measured at GSI at 400 MeV/nucleon.

   ↳ nucl-thnucl-exPRC(2024)·1 citation
6. 06*

   ML-based Calibration and Control of the GlueX Central Drift Chamber

   Thomas Britton🇺🇸 · Michael Goodrich🇺🇸 · Naomi Jarvis🇺🇸 · Torri Jeske🇺🇸 · Nikhil Kalra🇺🇸 · David Lawrence🇺🇸 · Diana McSpadden🇺🇸 · Kishan Rajput🇺🇸

   The GlueX Central Drift Chamber (CDC) in Hall D at Jefferson Lab, used for detecting and tracking charged particles, is calibrated and controlled during data taking using a Gaussian process. The system dynamically adjusts the high voltage applied to the anode wires inside the chamber in response to changing environmental and experimental conditions such that the gain is stabilized. Control policies have been established to manage the CDC's behavior. These policies are activated when the model's uncertainty exceeds a configurable threshold or during human-initiated tests during normal production running. We demonstrate the system reduces the time detector experts dedicate to calibration of the data offline, leading to a marked decrease in computing resource usage without compromising detector performance.

   ↳ physics.ins-detnucl-exJINST(2024)·1 citation

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.