Mon·Dec 8, 2025Monday·December 8, 2025

1. 01*

   Production of Light Nuclei in Au+Au Collisions at $\sqrt{s_{\mathrm{NN}}}=7.7-27$ GeV from STAR BES-II

   Yixuan Jin (for the STAR Collaboration)🇨🇳

   The studies of the production of light nuclei, such as deuteron and helium nuclei, in heavy-ion collisions are essential for understanding the dynamics of nuclear matter under extreme conditions. The yields and ratios of light nuclei serve as an effective method to distinguish between the thermal and coalescence models of light nuclei formation. Within the coalescence framework, the energy dependence of the coalescence parameters reflects the effective volume of the collision system, while in the thermal model yields are governed by chemical freeze-out conditions. The significantly larger datasets from the STAR Beam Energy Scan Phase II (BES-II), combined with enhanced detector capabilities, allow more precise and comprehensive measurements than phase I. In these proceedings, we present measurements of light nuclei production, including p, $\bar{\mathrm{p}}$, d, $\bar{\mathrm{d}}$, ${}^3\mathrm{He}$, in Au+Au collisions at BES-II energies of $\sqrt{s_{\mathrm{NN}}}=7.7-27$ GeV. The results include centrality-dependent transverse momentum spectra and yields ($\mathrm{d}N/\mathrm{d}y$), along with coalescence parameters $B_{\mathrm{A}}$ and particle yield ratios. The physics implications of these results are discussed.

   nucl-exhep-exnucl-thEPJ Web Conf.(2026)·1 citation
2. 02*

   Evidence for modest octupole deformation in ${}^{238}$U from high-energy heavy-ion collisions

   Chunjian Zhang (for the STAR Collaboration)🇨🇳

   We present a novel ``imaging-by-smashing" approach for probing nuclear deformation in high-energy heavy-ion collisions. By analyzing anisotropic-flow ($v_n$) and mean transverse momentum ($\left[p_T\right]$)-based observables in collisions of highly deformed ${}^{238}\mathrm{U}$ nucleus and nearly spherical ${}^{197}\mathrm{Au}$ nucleus, we extract the deformation parameters of ${}^{238}$U. The key observables include the variances $⟨v_n^2⟩,⟨{\left(\delta p_T\right)}^2⟩$, and the covariance $⟨v_n^2\delta p_T⟩$. Ratios of these observables between ${}^{238}$U+${}^{238}$U and ${}^{197}$Au+${}^{197}$Au collisions largely cancel final-state effects, thereby isolating the influence of nuclear deformation. We further report the first experimental indication of octupole deformation in ${}^{238}$U via $v_3$-based observables~\cite{2025rot}. The extracted deformation parameters, comparing with state-of-the-art hydrodynamic model calculations, are consistent with low-energy nuclear structure data. These results establish high-energy collisions as a powerful probe of nuclear shapes on femtosecond timescales.

   nucl-exhep-exEPJ Web Conf.(2026)·0 citations
3. 03*

   Measurements of Light Nuclei (d, t, ${}^3$He)-$\Lambda$ Correlations in Au+Au Collisions at $\sqrt{s_{NN}}=3$ GeV from STAR

   Xialei Jiang (for the STAR Collaboration)🇨🇳

   Heavy-ion collisions offer a unique way to study hyperon-nucleon ($Y$-$N$) interactions through two-particle momentum correlations, which reveal the source's space-time structure and the effects of the final state interactions. Correlations between light nuclei (d, t, ${}^3$He) and $\Lambda$ provide insight into hypernuclei structure, binding energies, and many-body interactions that might be relevant to the inner structure of neutron stars. This work presents the first measurements of d-$\Lambda$, t-$\Lambda$, and ${}^3$He-$\Lambda$ correlations from $\sqrt{s_{{}_{\mathrm{NN}}}}=3$ GeV Au+Au collisions collected in 2021 at STAR. Using the Lednicky-Lyuboshitz model, we extract source sizes and interaction parameters, shedding light on hyperon interactions and light hypernuclei structure.

   nucl-exhep-exEPJ Web Conf.(2026)·0 citations
4. 04*

   Constraining r-process nucleosynthesis via enhanced accuracy neutron-capture experiments

   C. Domingo-Pardo🇪🇸 · C. Lederer-Woods🇬🇧 · A. Mengoni🇨🇭

   The isotopic abundances of r-process elements in the solar system are traditionally derived as residuals from the subtraction of s-process contributions from total solar abundances. However, the uncertainties in s-process nucleosynthesis -- particularly those arising from Maxwellian Averaged Cross Sections (MACS) -- propagate directly into the r-process residuals, affecting their reliability. Building upon the seminal work of Goriely (1999), who introduced a multi-event s-process model to quantify these uncertainties, we revisit the problem using a simplified yet effective approach. By assuming that the relative uncertainty in s-process isotopic abundances scales linearly with the MACS uncertainties from data libraries (KADoNiS), we identify a subset of isotopes for which the r-process residuals remain significantly uncertain. Using updated solar abundances (Lodders 2025) and s-process contributions from Bisterzo et al. (2014), we present a short list of isotopes that are prime candidates for improved (n,g) measurements at CERN n_TOF in the near future. Our analysis provides a practical framework for prioritizing future experimental efforts that will profit from upgrades and enhancements of the n_TOF facility. It also highlights the need to revisit key neutron-capture cross sections to refine our understanding of the r-process isotopic abundance pattern, commonly used as a benchmark in stellar models of explosive nucleosynthesis.

   nucl-exastro-ph.SREPJA(2026)·0 citations
5. 05*

   GPU acceleration of optical photon propagation in low photon yield applications: Opticks for the Electron Ion Collider

   Gabor Galgoczi🇺🇸 · Kolja Kauder🇺🇸 · Maxim Potekhin🇺🇸 · Sakib Rahman🇺🇸 · Dmitri Smirnov🇺🇸 · Torre Wenaus🇺🇸

   The bulk of time spent in the simulation of Cherenkov and other scintillation detectors is spent on optical-photon transport, i.e. ray tracing, a task that GPUs are uniquely qualified to perform. We present EIC-Opticks, a fork of Opticks, which uses event aggregation to drastically accelerate photon transport simulation for low-to-moderate photon yield experiments. During the full Geant4 Monte Carlo simulation of a given detector, optical photon simulation is performed on GPU(s) using the NVIDIA OptiX framework. We validate this approach using the ePIC pfRICH detector. We find GPU and CPU simulations in excellent agreement. For $5\times 10^4$ electrons with a momentum of $p=5\mathrm{MeV}/c$ in the test case of the pfRICH detector, EIC-Opticks shows an order-of-magnitude speedup over multi-threaded Geant4, and a factor of up to 161$\pm$3 over single-threaded execution. In the case of low-to-moderate applications event aggregation reduces the per-photon simulation time from $\sim 60\mu \mathrm{s}$ for single events to $\sim 20\mathrm{ns}$ with batching, a factor of $\sim 3000$. In order to make EIC-Opticks easily installable, we authored a Spack package that makes it possible to install it with a single command. Additionally, a Docker container is provided for users with EIC-Opticks installed. EIC-Opticks provides guardrails for common pitfalls (e.g. nested volume conversion, ray tracing setting optimization).

   ↳ physics.ins-dethep-exnucl-exphysics.acc-phEPJC(2026)·3 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.