Wed·Feb 5, 2025Wednesday·February 5, 2025

1. 01*

   Absorption of $\psi (2S)$ mesons in nuclei

   E. Ya. Paryev🇷🇺

   In the present work we explore the inclusive $\psi (2S)$ meson photoproduction from nuclei near the kinematic threshold within the collision model, based on the nuclear spectral function, for incoherent direct photon--nucleon charmonium creation processes. The model takes into account the final $\psi (2S)$ absorption, target nucleon binding and Fermi motion. We calculate the absolute and relative excitation functions for production of $\psi (2S)$ mesons on ${}^{12}$C and ${}^{184}$W target nuclei at near-threshold photon beam energies of 8.0--16.4 GeV, the absolute momentum differential cross sections for their production off these target nuclei at laboratory polar angles of 0${}^{\circ }$--10${}^{\circ }$, the momentum dependence of the ratio of these cross sections as well as the A-dependences of the ratios (transparency ratios) of the total cross cross sections for $\psi (2S)$ production at photon energy of 13 GeV within the different scenarios for the $\psi (2S)N$ absorption cross section. We also calculate the A-dependence of the ratio of $\psi (2S)$ and $J/\psi$ photoproduction transparency ratios at photon energies around of 11.5 GeV within the adopted scenarios for this cross section. We demonstrate that both the absolute and relative observables considered reveal a definite sensitivity to these scenarios. Therefore, the measurement of such observables in future experiments at the upgraded up to 22 GeV CEBAF facility in the near-threshold energy region might shed light both on the $\psi (2S)N$ absorption cross section and on its part associated with the nondiagonal process $\psi (2S)+N\to J/\psi +N$ at finite momenta, which are of crucial importance in understanding of charmonium production and suppression in high-energy nucleus--nucleus collisions in a search for the quark-gluon plasma.

   ↳ nucl-thhep-phnucl-exNPA(2025)·1 citation
2. 02*

   Sensitivity of Double Deeply Virtual Compton Scattering observables to Generalized Parton Distributions

   J. S. Alvarado🇫🇷 · M. Hoballah🇫🇷 · E. Voutier🇫🇷

   Double Deeply Virtual Compton Scattering (DDVCS) is a promising channel for Generalized Parton Distribution (GPD) studies as it is a generalization of the Deeply Virtual Compton Scattering (DVCS) and Timelike Compton Scattering (TCS) processes. Contrary to DVCS and TCS, the GPD phase space accessed through DDVCS is not constrained by on-shell conditions on the incoming and outgoing photons thus allowing unrestricted GPD extraction from experimental observables. Considering polarized electron and positron beams directed to a polarized proton target, we study the sensitivity of the DDVCS cross-section asymmetries to the chiral-even proton GPDs from different model predictions. The feasibility of such measurements is further investigated in the context of the CLAS and SoLID spectrometers at the Thomas Jefferson National Accelerator Facility and the future Electron-Ion Collider at the Brookhaven National Laboratory.

   ↳ hep-phnucl-exPRC(2025)·10 citations
3. 03*

   Signal shape studies and rate dependence of HFO-based gas mixtures in RPC detectors

   L. Quaglia🇮🇹 · M. Abbrescia🇮🇹 · G. Aielli🇮🇹 · R. Aly🇮🇹 · M. C. Arena🇮🇹 · M. Barroso🇧🇷 · L. Benussi🇮🇹 · S. Bianco🇮🇹 · F. Bordon🇨🇭 · D. Boscherini🇮🇹 · A. Bruni🇮🇹 · S. Buontempo🇮🇹 and 47 other authors

   The RPCs employed at the LHC experiments are currently operated in avalanche mode, with a mixture containing a large fraction of C${}_2$H${}_2$F${}_4$ ($\approx$90\% or more) with the addition of i-C${}_4$H${}_{10}$ and SF${}_6$ in different concentrations. However, C${}_2$H${}_2$F${}_4$ and SF${}_6$ are fluorinated greenhouse gases (F-gases) with Global Warming Potential (GWP) of $\approx$1400 and $\approx$22800, respectively. EU regulations imposed a progressive phase-down of C${}_2$H${}_2$F${}_4$ production and consumption, aiming at strongly reducing its emission. This is already resulting in an increase of its price and reduction in availability. The most desirable long-term solution to this problem is to find an alternative, F-gases-free gas mixture, able to maintain similar detector performance. To address this challenge, the RPC ECOGasas@GIF++ collaboration (including RPC experts of ALICE, ATLAS, CMS, SHiP/LHCb, and the CERN EP-DT group) was created in 2019. The collaboration is currently studying a gas from the olefine family, the C${}_3$H${}_2$F${}_4$ (or simply HFO, with GWP $\approx$6), to be used, in combination with CO${}_2$, as a substitute for C${}_2$H${}_2$F${}_4$. This contribution will focus on the signal shape studies that have been carried out by the collaboration during dedicated beam test periods. The methodology used in the data analysis will be presented, together with the results obtained with several HFO-based gas mixtures, and with the currently employed one. Furthermore, results on the counting-rate dependence of the RPC performance, obtained by combining the muon beam with the GIF++ ${}^{137}$Cs source with different attenuation factors, will also be presented.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2025)·2 citations

* 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.