Tue·Apr 29, 2025Tuesday·April 29, 2025

1. 01*

   Generative Models for Fast Simulation of Cherenkov Detectors at the Electron-Ion Collider

   James Giroux🇺🇸 · Michael Martinez🇺🇸 · Cristiano Fanelli🇺🇸

   The integration of Deep Learning (DL) into experimental nuclear and particle physics has driven significant progress in simulation and reconstruction workflows. However, traditional simulation frameworks such as Geant4 remain computationally intensive, especially for Cherenkov detectors, where simulating optical photon transport through complex geometries and reflective surfaces introduces a major bottleneck. To address this, we present an open, standalone fast simulation tool for Detection of Internally Reflected Cherenkov Light (DIRC) detectors, with a focus on the High-Performance DIRC (hpDIRC) at the future Electron-Ion Collider (EIC). Our framework incorporates a suite of generative models tailored to accelerate particle identification (PID) tasks by offering a scalable, GPU-accelerated alternative to full Geant4-based simulations. Designed with accessibility in mind, our simulation package enables both DL researchers and physicists to efficiently generate high-fidelity large-scale datasets on demand, without relying on complex traditional simulation stacks. This flexibility supports the development and benchmarking of novel DL-driven PID methods. Moreover, this fast simulation pipeline represents a critical step toward enabling EIC-wide PID strategies that depend on virtually unlimited simulated samples, spanning the full acceptance of the hpDIRC.

   ↳ physics.ins-detcs.AIcs.LGhep-ex+1Mach.Learn.Sci.Tech.(2025)·5 citations
2. 02*

   Disentangling effects of nucleon size and nucleus structure in relativistic heavy-ion collisions

   Hai-Cheng Wang🇨🇳 · Song-Jie Li🇨🇳 · Jun Xu🇨🇳 · Zhong-Zhou Ren🇨🇳

   While relativistic heavy-ion collisions become an alternative way of studying nucleus structure, the accurate extraction of nucleus structure could be hampered by the uncertainty of nucleon size, and the latter has attracted people's attention in the past few years. We have compared the impacts of nuclear size and nucleus structure on deformation probes in relativistic heavy-ion collisions based on a multiphase transport (AMPT) model. With increasing nucleon size, the absolute values of the deformation probes are generally reduced due to smeared initial density fluctuations. In heavy systems such as ${}^{197}$Au+${}^{197}$Au collisions, neglecting the nucleon size could underestimate or overestimate significantly the extracted deformation parameter depending on the used deformation probe, while the scaled anisotropic flow and the scaled Pearson correlation coefficient of flow and transverse momentum are good probes of the nucleus deformation rather insensitive to the nucleon size. In small systems such as ${}^{16}$O+${}^{16}$O collisions, the deformation probes are generally more sensitive to the nucleon size than to the nucleus structure, and the transverse momentum fluctuation less sensitive to detailed nucleus structure may serve as a good probe of the nucleon size.

   ↳ nucl-thhep-exnucl-exPLB(2025)·1 citation
3. 03*

   Search for high energy 5.5 MeV solar axions with the complete Borexino dataset

   Borexino Collaboration

   A search for solar axions and axion-like particles produced in the $p+d\to {}^3\mathrm{He}+\mathrm{A}(5.5\mathrm{MeV})$ reaction was performed using the complete dataset of the Borexino detector (3995 days of measurement live-time). The following interaction processes have been considered: axion decay into two photons $(\mathrm{A}\to 2\gamma )$, inverse Primakoff conversion on nuclei $(\mathrm{A}+Z\to \gamma +Z$), the Compton conversion of axions to photons $(\mathrm{A}+e\to e+\gamma )$ and the axio-electric effect $(\mathrm{A}+e+Z\to e+Z$). Model-independent limits on axion-photon ($g_{A\gamma }$), axion-electron ($g_{Ae}$), and isovector axion-nucleon ($g_{3AN}$) couplings are obtained: $|g_{A\gamma }\times g_{3AN}|\le 2.3\times 10^{-11}{\mathrm{GeV}}^{-1}$ and $|g_{Ae}\times g_{3AN}|\le 1.9\times 10^{-13}$ at $m_A<$ 1 MeV (90\% c.l.). The Borexino results exclude new large regions of $g_{A\gamma }$, and $g_{Ae}$ coupling constants and axion masses $m_A$, and leads to constraints on the products $|g_{A\gamma }\times m_A|$ and $|g_{Ae}\times m_A|$ for the KSVZ- and the DFSZ-axion models.

   ↳ hep-exastro-ph.SRhep-phnucl-exEPJC(2025)·6 citations
4. 04*

   A "breathing'' octupole ${}^{208}$Pb nucleus: resolving the elliptical-to-triangular azimuthal anisotropy puzzle in ultracentral relativistic heavy ion collisions

   Hao-jie Xu🇨🇳 · Duoduo Xu🇨🇳 · Shujun Zhao🇨🇳 · Wenbin Zhao🇺🇸 · Huichao Song🇨🇳 · Fuqiang Wang🇺🇸

   Relativistic heavy ion collisions provide a unique opportunity to probe the nuclear structure by taking an instantaneous snapshot of the colliding nuclei and converting it into momentum anisotropies of final emitted hadrons. A long-standing puzzle of too large a ratio of the elliptical-to-triangular ($v_2$-to-$v_3$) anisotropies in ultracentral ${}^{208}$Pb+${}^{208}$Pb collisions at the Large Hadron Collider(LHC) cannot be solved simply by hydrodynamic simulations with initial conditions containing the spherical or certain deformed shape of ${}^{208}$Pb. In this Letter, using the iEBE-VISHNU relativistic viscous hydrodynamic hybrid model simulations with the Trento initial condition, we show that a dynamic octupole deformation--a shape-breathing of ${}^{208}$Pb --could potentially solve the $v_2$-to-$v_3$ puzzle and simultaneously describe the $v_3\{4\}$ data measured in experiment. Our results highlight the unique capability of capturing transient collective properties of nuclei on yoctosecond ($10^{-24}$~s) timescales, unfeasible with low-energy nuclear reactions.

   ↳ nucl-thnucl-exPRC(2025)·11 citations
5. 05*

   The shape of differential radial flow $v_0(p_T)$, not its zero-crossing, carries physical information

   Somadutta Bhatta🇺🇸 · Aman Dimri🇺🇸 · Jiangyong Jia🇺🇸

   Radial flow, a key collective phenomenon in heavy-ion collisions, manifests itself through event-by-event fluctuations of transverse-momentum ($p_{\mathrm{T}}$) spectra. The $p_{\mathrm{T}}$-differential radial flow observable, $v_0(p_{\mathrm{T}})$, was introduced to quantify local spectral-shape fluctuations, but it is unavoidably influenced by global multiplicity fluctuations. Using the HIJING model, we show that different event-activity definitions for centrality classification and different spectral normalization schemes generate a constant vertical offset in $v_0(p_{\mathrm{T}})$ without altering its shape. This offset reflects the impact of residual volume/centrality fluctuations rather than genuine dynamical radial flow fluctuations. Accordingly, only the shape of $v_0(p_{\mathrm{T}})$, or equivalently its derivative $d{v}_0(p_{\mathrm{T}})/d{p}_{\mathrm{T}}$, carries physical information about radial-flow dynamics; its zero crossing does not. Practical implications include the need to vertically align measurements from different experiments before comparison, thereby removing normalization ambiguities when constraining QGP properties.

   ↳ nucl-thhep-phnucl-exNucl.Sci.Tech.(2026)·7 citations
6. 06*

   Gas-cell development for nuclear astrophysics motivated studies on noble gas targets and the ${}^3$He($\alpha$,$\gamma$)${}^7$Be reaction

   Á. Tóth · Z. Elekes🇭🇺 · Zs. Fülöp · Gy. Gyürky🇭🇺 · Z. Halász🇭🇺 · M. M. Juhász · G. G. Kiss🇭🇺 · S. R. Kovács · Zs. Mátyus · T. N. Szegedi · T. Szücs🇭🇺

   In many astrophysical scenarios, alpha induced reactions on noble gas nuclei play a crucial role. Studying these reactions in the laboratory requires the noble gas atoms to be confined in a sufficient amount to allow the reactions. At Atomki thin-windowed gas-cell targets were developed and improved for studying alpha induced reactions on noble gases. Several stages of the gas-cell design used for activation experiments and lately a version to be used for particle scattering experiments will be presented. A new experimental study of the ${}^3$He($\alpha$,$\gamma$)${}^7$Be reaction with one of the activation gas-cell targets was performed. This reaction plays an important role both in the solar pp-chains and in big bang nucleosynthesis. The reaction cross section was measured in the past in several works, however, there are still energy regions lacking experimental data, rendering the extrapolations towards the astrophysically relevant energies uncertain. New experimental total cross section of the ${}^3$He($\alpha$,$\gamma$)${}^7$Be reaction was thus determined here in the energy range of $E_{c.m.}=2600-3000$ keV in about 50 keV energy steps. These results confirm the overall trend, and also the absolute scale set by the only one previous measurement in this energy range. In addition, two pilot experiments with the scattering cell were performed aiming to study the ${}^4$He($\alpha$,$\alpha$)${}^4$He and ${}^{124}$Xe($\alpha$,$\alpha$)${}^{124}$Xe reactions at $E_{\alpha }=18$ MeV. These studies benchmark the performance of the cell and detection system both for light and heavy noble gas targets.

   ↳ physics.ins-detnucl-exEPJA(2025)·0 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.