Thu·May 1, 2025Thursday·May 1, 2025

1. 01*

   Measurement of single- and double-polarization observables in the photoproduction of ${\pi }^{+}{\pi }^{-}$~meson pairs off the proton using CLAS at Jefferson Laboratory

   P. Roy🇺🇸 · S. Cao · V. Crede🇺🇸 · E. Klempt🇩🇪 · V. A. Nikonov🇩🇪 · A. V. Sarantsev🇷🇺 · V. D. Burkert🇺🇸 · V. Mokeev🇺🇸 · P. Achenbach🇺🇸 · J. S. Alvarado🇫🇷 · W. R. Armstrong🇺🇸 · H. Atac🇺🇸 and 132 other authors

   The photoproduction of ${\pi }^{+}{\pi }^{-}$ meson pairs off the proton has been studied in the reaction $\gamma p\to p{\pi }^{+}{\pi }^{-}$ using the CEBAF Large Acceptance Spectrometer (CLAS) and the frozen-spin target (FROST) in Hall B at the Thomas Jefferson National Accelerator Facility. For the first time, the beam and target asymmetries, $I^{s,c}$ and $P_{x,y}$, have been measured along with the beam-target double-polarization observables, $P_{x,y}^{s,c}$, using a transversely polarized target with center-of-mass energies ranging from 1.51 GeV up to 2.04 GeV. These data and additional $\pi \pi$ photoproduction observables from CLAS and experiments elsewhere were included in a partial-wave analysis within the Bonn-Gatchina framework. Significant contributions from $s$-channel resonance production are observed in addition to $t$-channel exchange processes. The data indicate significant contributions from $N^{\ast }$ and ${\Delta }^{\ast }$ resonances in the third and fourth resonance regions.

   nucl-exPRC(2025)·1 citation
2. 02*

   Potential for Tensor Polarized Deuterons in Hall D at Jefferson Lab

   Mark M. Dalton · Alexandre Deur · Chris Keith

   Hall D at Jefferson lab is an ideal place to install a polarized deuteron target which can be ''tensor polarized", allowing the separation of the spin states $m=0,\pm 1$ or the measurement of tensor asymmetries. The bremsstrahlung photon beam with 12 GeV endpoint provides very little heating or radiation damage compared to an electron beam, allowing the target to be run in frozen spin mode. Adiabatic fast passage spin manipulations can then be used to greatly enhance the population of the m=0 spin state of the deuteron. Coherent photoproduction of $\rho$ mesons from deuterium is sensitive to double-scattering at high momentum transfer and in the m=0 spin state an additional sensitivity at intermediate momentum transfer opens up. We propose a frozen spin target for Hall D and the measurement of $\rho$ photoproduced coherently from the deuteron as a flagship measurement.

   nucl-exEPJA(2025)·2 citations
3. 03*

   Electron beam characterization via fluorescence imaging of Rydberg states in atomic vapor

   Rob Behary · Kevin Su · Nicolas DeStefano · Mykhailo Vorobiov · T. Averett🇺🇸 · Alexandre Camsonne🇺🇸 · Shukui Zhang🇨🇳 · Charlie Fancher · Neel Malvania · Eugeniy Mikhailov · Seth Aubin · Irina Novikova

   We demonstrate an all-optical, minimally invasive method for electron beam (e-beam) characterization using Rydberg electrometry. The e-beam passes through a dilute Rb vapor prepared in a quantum superposition of ground and Rydberg states that reduces resonant absorption in a narrow spectral region. Imaging the modifications of Rb fluorescence due to shifts in the Rydberg state from the e-beam electric field allows us to reconstruct e-beam width, centroid position, and current. We experimentally demonstrate this technique using a 20 keV e-beam in the range of currents down to 20 $\mu$A, and discuss technical challenges produced by environmental electric potentials in the detection chamber. Overall, we demonstrate the promising potential of such an approach as a minimally invasive diagnostic for charged particle beams.

   ↳ physics.atom-phnucl-exphysics.acc-phquant-ph0 citations
4. 04*

   Do QGP Droplets Drive Anisotropy in Small Systems? Insights from RHIC and the LHC

   Roy A. Lacey (Department of Chemistry, Stony Brook University, Stony Brook, NY, USA)🇺🇸

   Azimuthal anisotropy scaling functions for identified mesons and baryons are analyzed in large (Pb+Pb at $\sqrt{s_{NN}}=2.76$ and 5.02 TeV, Au+Au at $\sqrt{s_{NN}}=200$ GeV), intermediate (Cu+Cu at $\sqrt{s_{NN}}=200$~GeV), and small (p+Pb at $\sqrt{s_{NN}}=5.02$ and 8.16 TeV, p+Au, d+Au, and ${}^3$He+Au at $\sqrt{s_{NN}}=200$ GeV) collision systems. The scaling functions' fidelity supports a hydrodynamic-like origin for anisotropies in the flow-dominated regime. Central Pb+Pb, Au+Au, and Cu+Cu reflect QGP-driven expansion with strong radial flow and significant jet quenching, while peripheral Pb+Pb and Cu+Cu exhibit hadronic-dominated dynamics. In contrast, central RHIC small systems show hadronic-dominated behavior, with strong re-scattering, negligible radial flow, and suppressed jet quenching, following the hierarchy p+Au $>$ d+Au $>$ ${}^3$He+Au. At the LHC, ultra-central p+Pb collisions display enhanced radial flow, reduced re-scattering, and small but nonzero jet quenching. Scaling violations at high $p_T$ reflect partial suppression of partonic energy loss. These findings demonstrate that QGP-like behavior in small systems depends sensitively on both system size and beam energy, and establish the scaling framework as a robust diagnostic of collectivity and medium properties across diverse collision conditions.

   ↳ hep-exhep-phhep-thnucl-ex1 citation
5. 05*

   Double nuclear modification factor in relativistic heavy ion collisions

   A.S. Chernyshov🇷🇺 · I.P. Lokhtin🇷🇺 · A.M.Snigirev🇷🇺

   The hypothesis of the factorization of the double nuclear modification factor in relativistic heavy ion collisions is tested for different types of final-state hadrons within the HYDJET++ model. The results demonstrate that this factorization holds reasonably well at moderately high transverse momenta, provided that the effects of double parton scattering can be small or neglected.

   ↳ nucl-thhep-phnucl-exJETP Lett.(2025)·0 citations
6. 06*

   Thermoelectric Thomson coefficient of quark-gluon plasma in the presence of a time-varying magnetic field

   Kamaljeet Singh🇮🇳 · Raghunath Sahoo🇮🇳

   Heavy-ion collision experiments such as the Large Hadron Collider and the Relativistic Heavy Ion Collider offer a unique platform to study several key properties of the quark-gluon plasma (QGP), a deconfined state of strongly interacting matter. Quarks, being the electrically charged particles, can induce an electric current in the medium in response to the temperature gradients. Hence, the QGP medium can behave like a thermoelectric medium. The thermoelectric coefficients, such as the Seebeck and Thomson coefficients, can help us to understand the intricate transport phenomenon of the medium. In peripheral collisions, the intense, transient, and time-dependent magnetic field created due to spectator protons significantly influences the thermoelectric properties of the QGP medium, affecting the charge and heat transport. This work uses the quasi-particle model to calculate the Thomson coefficient in QGP. The Thomson effect, describing the continuous heating or cooling of the charge-carrying medium in the presence of temperature gradients, remains largely unexplored in QGP. The Seebeck effect, which relates temperature gradients to induced electric fields, has been widely studied in the literature. For the first time, we calculate the magneto-Thomson and transverse Thomson coefficients. We have studied their dependence on temperature, baryon chemical potential, center of mass energy, and time-dependent magnetic field with different decay parameters. The transverse Thomson effect originates due to the presence of the Nernst effect in the presence of a magnetic field. Our results provide new insights into the higher-order thermoelectric transport properties of the QGP medium in the context of heavy-ion collisions.

   ↳ hep-phhep-exhep-thnucl-ex+1PRD(2025)·7 citations
7. 07*

   Characterisation of the neutron beam in the n_TOF-EAR2 experimental area at CERN following the spallation target upgrade

   J.A. Pavon-Rodriguez · J. Lerendegui-Marco · A. Manna · S. Amaducci · M. Sabate-Gilarte · E. Musacchio-Gonzalez · M. Bacak · V. Alcayne · M.A. · Cortes-Giraldo · V. Vlachoudis · R. Zarrella and 7 other authors

   The n_TOF facility at CERN has undergone a major upgrade after the installation of a new spallation target, designed to improve the features of both neutron beamlines at the experimental areas 1 and 2 (EAR1 and EAR2) and the commissioning of a new experimental area (NEAR). Due to improved coupling of the spallation target with the EAR2 beamline, the upgrade resulted in a significantly increased neutron flux and improved neutron energy resolution. This paper presents the results of the commissioning phase that followed to characterise the EAR2 neutron beamline and validate the FLUKA Monte Carlo simulations of the facility. The main features of the neutron beam, namely the neutron flux, spatial profile and energy resolution, are evaluated and compared to the previous target. The neutron flux presents a general increase of 20% below 1 eV, 40% between 1 eV and 100 keV and 50% between 100 keV and 10 MeV. The measured width of the beam profile was 3 cm (FWHM) at the reference position for neutron capture measurements. The energy resolution with the new spallation target shows a significant improvement compared to the previous one. Moreover, FLUKA Monte Carlo simulations present a good agreement with the measured neutron flux and profile within uncertainties, and a remarkable reproduction of the energy resolution.

   ↳ physics.ins-dethep-exnucl-exEPJA(2025)·6 citations
8. 08*

   Full realization of the RIBLL2 separator at the HIRFL-CSR facility

   Xiao-Dong Xu🇨🇳 · Yong Zheng · Zhi-Yu Sun🇨🇳 · Yu-Nan Song · Bao-Hua Sun · Satoru Terashima🇨🇳 · Chang-Jian Wang🇨🇳 · Ge Guo🇨🇳 · Guang-Shuai Li · Xiu-Lin Wei🇨🇳 · Jun-Yao Xu🇨🇳 · Ji-Chao Zhang and 24 other authors

   A new experimental platform was constructed at the Second Radioactive Ion Beam Line in Lanzhou (RIBLL2) of HIRFL-CSR accelerator facility at Lanzhou, China. Its performance, along with several newly developed detectors, was tested in two radioactive ion beam experiments utilizing a 400 MeV/u 40Ar beam and a 350 MeV/u 78Kr beam, respectively. The first results from these two experiments demonstrate a good particle identification capability of the setup, thereby affirming the full realization of the RIBLL2 separator.

   ↳ physics.ins-detnucl-exphysics.acc-phSci.Bull.(2025)·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.