Wed·May 7, 2025Wednesday·May 7, 2025

1. 01*

   Proceedings of Direct photon measurement in small systems and thermal radiation from QGP with ALICE, Hard Probes conference 2024

   Jerome Jung (for the ALICE Collaboration)🇩🇪

   Electromagnetic probes are a unique tool for studying the space-time evolution of the hot and dense matter created in ultra-relativistic heavy-ion collisions. Dielectrons are emitted during the entire evolution of the medium created in such collisions, allowing the extraction of the real direct photon fraction at vanishing mass and providing access to thermal radiation from the early hot stages of the collision. The measurement of dielectron and direct-photon production in minimum-bias pp collisions serves as a crucial baseline for the studies in heavy-ion collisions, whereas pp collisions with high charged-particle multiplicities allow the search for the possible presence of QGP in small systems. An overview of the final results of dielectron production in pp at $\sqrt{s}=13$ TeV and in central \PbPb collisions at \fivenn measured by ALICE is presented, together with their implications for the production of thermal radiation. Finally, an outlook on future measurements is given with the first performance studies from Run 3.

   nucl-exhep-ex1 citation
2. 02*

   A Continuous Galactic Line Source of Axions: The Remarkable Case of 23Na

   W. C. Haxton🇺🇸 · Xing Liu🇺🇸 · Annie McCutcheon🇺🇸 · Anupam Ray🇺🇸

   We argue that ${}^{23}$Na is a potentially significant source of galactic axions. For temperatures $\gtrsim 7\times 10^8$K -- characteristic of carbon burning in the massive progenitors of supernovae and ONeMg white dwarfs -- the 440 keV first excited state of ${}^{23}$Na is thermally populated, with its repeated decays pumping stellar energy into escaping axions. Odd-A nuclear abundances are typically very low in high-temperature stellar environments (or absent entirely due to burn-up). ${}^{23}$Na is an exception: $\approx 0.1M_{\odot }$ of the isotope is synthesized during carbon burning then maintained at $\approx 10^9$K for times ranging up to $6\times 10^4$y. Using MESA simulations, a galactic model, and sampling over progenitor masses, locations, and evolutionary stages, we find a continuous flux at earth of $⟨{\varphi }_a⟩\approx 22$/cm${}^2$s for $g_{aNN}^{\mathrm{eff}}=10^{-9}$. Some fraction of these axions convert to photons as they propagate through the galactic magnetic field, producing a distinctive 440 keV line $\gamma$ ray detectable by all-sky detectors like the Compton Spectrometer and Imager (COSI). Assuming a 1$\mu$G galactic magnetic field and a sufficiently light axion mass, we find that COSI will be able to probe $|g_{aNN}^{\mathrm{eff}}{g}_{a\gamma \gamma }|\gtrsim 1.8\times 10^{-22}$ GeV${}^{-1}$ at $3\sigma$ after two years of surveying.

   ↳ astro-ph.HEhep-exhep-phnucl-ex+1PRL(2025)·5 citations
3. 03*

   A Centrality-independent Framework for Revealing Genuine Higher-Order Cumulants in Heavy-Ion Collisions

   Zhaohui Wang🇨🇳 · Xiaofeng Luo🇨🇳

   We propose a novel centrality definition-independent method for analyzing higher-order cumulants, specifically addressing the challenge of volume fluctuations that dominate in low-energy heavy-ion collisions. This method reconstructs particle number distributions using the Edgeworth expansion, with parameters optimized via a combination of differential evolution algorithm and Bayesian inference. Its effectiveness is validated using UrQMD model simulations and benchmarked against traditional approaches, including centrality definitions based on particle multiplicity. Our results show that the proposed framework yields cumulant patterns consistent with those obtained using number of participant nucleon ($N_{\text{part}}$) based centrality observables, while eliminating the conventional reliance on centrality determination. This consistency confirms the method's ability to extract genuine physical signals, thereby paving the way for probing the intrinsic thermodynamic properties of the produced medium through event-by-event fluctuations.

   ↳ physics.data-anhep-exhep-thnucl-ex+1PLB(2025)·8 citations
4. 04*

   X-ray-induced quenching of the ${}^{229}$Th clock isomer in CaF${}_2$

   Ming Guan · Michael Bartokos🇦🇹 · Kjeld Beeks🇦🇹 · Hiroyuki Fujimoto🇯🇵 · Yuta Fukunaga · Hiromitsu Haba · Takahiro Hiraki · Yoshitaka Kasamatsu🇯🇵 · Shinji Kitao · Adrian Leitner · Takahiko Masuda🇯🇵 · Nobumoto Nagasawa and 18 other authors

   Thorium-229 has the lowest nuclear-excited state (an isomer state) at approximately 8.356 eV, making it excitable with tabletop vacuum-ultraviolet lasers. Despite the recent success of laser excitation, the isomer quenching inside the solid-state environment remains unresolved. In this letter, we present experiments investigating X-ray-induced isomer quenching in the CaF${}_2$ host, focusing on the effects of X-ray flux and temperature on the lifetime and yield of the isomer state. Our studies reveal a correlation between isomer production, isomer lifetime during irradiation, and post-irradiation afterglow of the target crystal across different temperatures, highlighting a strong relationship between isomer quenching and color-center dynamics. We developed a model to interpret the isomer quenching and the crystal's luminescence.

   ↳ cond-mat.mtrl-scinucl-exPRL(2026)·9 citations
5. 05*

   Parameterizations of Electron Scattering Form Factors for Elastic Scattering and Electro-Excitation of Nuclear States for ${}^{27}\mathrm{Al}$ and ${}^{40}\mathrm{Ca}$

   Arie Bodek🇺🇸 · M. E. Christy🇺🇸 · Zihao Lin🇺🇸 · Giulia-Maria Bulugean🇺🇸 · Amii Daniela Matamoros Delgado

   We report on empirical parameterizations of longitudinal (${\mathcal{R}}_L$) and transverse (${\mathcal{R}}_T$) nuclear electromagnetic form factors for elastic scattering and the excitations of nuclear states in ${}^{27}\mathrm{Al}$ and ${}^{40}\mathrm{Ca}$. The parameterizations are needed for the calculations of radiative corrections in measurements of electron scattering cross sections on ${}^{27}\mathrm{Al}$ and ${}^{40}\mathrm{Ca}$ in the quasi-elastic, resonance and inelastic continuum regions, provide the contribution of nuclear excitations in investigations of the Coulomb Sum Rule, and test theoretical model predictions for excitation of nuclear states in electron and neutrino interactions on nuclear targets at low energies.

   ↳ nucl-thnucl-exPRC(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.