Mon·Nov 10, 2025Monday·November 10, 2025

1. 01*

   Charged-Particle Multiplicity Dependence of Net-Proton Cumulants in Zr+Zr and Ru+Ru Collisions at $\sqrt{s_{NN}}$ = 200 GeV

   The STAR Collaboration

   We present measurements of cumulants of event-by-event net-proton distribution at mid-rapidity and their ratios up to the sixth order as a function of charged-particle multiplicity in Zr+Zr and Ru+Ru(isobars) collisions at a nucleon-nucleon center-of-mass energy ($\sqrt{s_{NN}}$) of 200 GeV. The data are collected from the STAR experiment with a total of two billion events recorded for each collision system. The measurements are compared with those obtained from p+p and Au+Au collision systems at the same center-of-mass energy. The higher-order cumulant ratios ($C_4/C_2$, $C_5/C_1$, and $C_6/C_2$) show an overall decreasing trend as a function of the charged-particle multiplicity across systems. The isobar results align with the Au+Au trends within uncertainties. The observations are compared with calculations from Lattice Gauge Theory (LGT) that include a quark-hadron crossover. The systematic behavior of the higher-order cumulant ratios shows that, overall, they progressively approach LGT predictions with increasing multiplicity within uncertainties. This could imply that the medium created in these heavy-ion collisions gradually evolves into thermalized QCD matter undergoing a crossover transition with multiplicity.

   nucl-ex1 citation
2. 02*

   Opportunities for Imaging Light Nuclei with a Second Interaction Region at the Electron-Ion Collider

   Wan Chang🇨🇳 · Elke-Caroline Aschenauer🇺🇸 · Alexander Jentsch🇺🇸 · Arjun Kumar🇺🇸 · Zhoudunming Tu🇺🇸 · Zhongbao Yin🇨🇳

   The upcoming Electron-Ion Collider (EIC) will address several outstanding puzzles in modern nuclear physics. Key questions-such as the partonic structure of nucleons and nuclei and the origin of their mass and spin-can be explored through high-energy electron-proton and electron-nucleus collisions. To maximize its scientific reach, the EIC community has advocated for the addition of a second interaction region equipped with a detector complementary to the EIC general purpose collider detector, ePIC. The pre-conceptual design of this interaction region aims to provide a different configuration from the first interaction region, which enhances forward acceptance at very small scattering angles ($\theta \sim 0$ mrad). This machine configuration would significantly benefit exclusive, tagging, and diffractive physics programs, complementing those of the ePIC experiment. In particular, accessing coherent diffractive processes on light nuclei by tagging of the full, intact nucleus is essential for mapping their spatial parton distributions. In this work, we present an exploratory study of the detection capabilities for light nuclei at a second EIC interaction region, with a detailed discussion of the accessible kinematic phase space and its implications for imaging.

   nucl-exhep-exhep-phPRD(2026)·2 citations
3. 03*

   Optical studies of scintillation detectors for precision beta-energy measurements

   S. Vanlangendonck🇧🇪 · D. Atanasov🇧🇪 · B. Blank🇫🇷 · X. Fléchard🇫🇷 · M. Kanafani🇫🇷 · S. Lecanuet🇫🇷 · O. Naviliat-Cuncic🇫🇷 · N. Severijns🇧🇪 · M. Versteegen🇫🇷

   This work presents optical calculations and simulations for scintillation detectors used in precision measurements of beta-particle energy spectra. Particular attention is given to Cherenkov photons and the impact of the light detection efficiency in the detector ensemble. We present an approach to estimate this light detection efficiency from the measured energy resolution of a detector. This is essential for the inclusion of scintillation photons in optical tracking Monte-Carlo simulations. A method to account for possible saturation and cross-talk of silicon photo-multipliers is also discussed. The impact of these effects is quantified in terms of systematic shifts in the extraction of the Fierz interference term from measurements of beta-energy spectra using scintillator detectors.

   ↳ physics.ins-detnucl-ex0 citations
4. 04*

   ${}^{42}$Ar Production and Injection to a Liquid Argon Environment for Background Mitigation Studies

   Mario Schwarz🇩🇪 · Christoph Vogl🇩🇪 · Niko N. P. N. Lay🇩🇪 · Tommaso Comellato🇩🇪 · Gunther Korschinek🇩🇪 · Moritz Neuberger🇩🇪 · Oskar Moras🇩🇪 · Patrick Krause🇩🇪 · Stefan Schönert🇩🇪

   Atmosphere-sourced argon contains traces of ${}^{42}$Ar, whose ${\beta }^{-}$-decaying progeny ${}^{42}$K represents a significant intrinsic background for rare-event experiments using liquid argon (LAr) as detector or shielding medium. Understanding and mitigating this background is crucial for current and future large-scale detectors in neutrino and dark-matter physics. To enable controlled studies of ${}^{42}$K behavior and suppression techniques, ${}^{42}$Ar was produced by irradiating natural argon with 34 MeV ${}^7$Li${}^{3+}$ ions at the Maier-Leibnitz-Laboratorium tandem accelerator, using beam currents of $101\pm 5$ nA and $140\pm 5$ nA, yielding $476\pm 9$ Bq within two weeks, corresponding to a production rate of $\sim 1\times 10^6$ atomss${}^{-1}$. The activated argon was injected into the one-ton SCARF cryostat, where two HPGe detectors monitored the subsequent ${}^{42}$K activity build-up. A time-dependent model describing ${}^{42}$Ar mixing and ${}^{42}$K equilibration in LAr yielded characteristic mixing time constants between one and two days. The established production and injection capability provides a reproducible platform for high-statistics ${}^{42}$K background studies, essential for developing and validating suppression strategies for next-generation LAr-based rare-event experiments such as LEGEND-1000.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2026)·1 citation
5. 05*

   The $Z{\alpha }^2$ correction to superallowed beta decays in effective field theory and implications for $|V_{ud}|$

   Zehua Cao🇺🇸 · Richard J. Hill🇺🇸 · Ryan Plestid🇺🇸 · Peter Vander Griend🇺🇸

   Superallowed ($0^{+}\to 0^{+}$) beta decays currently provide the most precise extraction of quark mixing in the Standard Model. Their interpretation as a measurement of $|V_{ud}|$ relies on a reliable first-principles computation of QED radiative corrections expressed as a series in $Z\alpha$ and $\alpha$. In this work, we provide the first model-independent result for two-loop, $O(Z{\alpha }^2)$, long-distance radiative corrections where the nuclei are treated as heavy point-like particles. We use renormalization group analysis to obtain new results at $O(Z{\alpha }^3)$ for the coefficient of double-logarithms in the ratio of the maximal beta energy to the inverse nuclear size, $\text{Em}/R^{-1}$. We use the Kinoshita-Lee-Nauenberg theorem to obtain new results at $O(Z^2{\alpha }^3)$ for the coefficient of logarithms in the ratio of maximal beta energy to the electron mass, $\log (2\text{Em}/\text{me})$. We identify a structure-dependent, and therefore short-distance, contribution to the traditional $Z{\alpha }^2$ correction that should be revisited.. We provide the first comprehensive update to the long-distance corrections in almost forty years and comment on the impact of our findings for extractions of $|V_{ud}|$. We find that shifts in the long-distance corrections are $2.5\times$ larger than past estimates of their uncertainty, $1.5\times$ larger than the statistical uncertainty from the combined fit of superallowed decays, and about $1/2$ the size of estimated systematic error, which stems dominantly from nuclear structure effects.

   ↳ hep-phnucl-exnucl-thPRD(2026)·11 citations
6. 06*

   Radiative corrections to superallowed beta decays at $\mathcal{O}({\alpha }^{2}Z)$

   Òscar L. Crosas🇨🇭 · Emanuele Mereghetti🇺🇸

   We compute $\mathcal{O}({\alpha }^{2}Z)$ radiative corrections to superallowed $\beta$ decays with a heavy-particle effective field theory that systematically describes the interactions of low-energy ultrasoft photons with nuclei. We calculate two-loop virtual and one-loop real-virtual amplitudes by reducing the Feynman integrals to a set of master integrals, which we solve analytically using a variety of techniques. These techniques can be applied to other phenomenologically interesting observables. The ultrasoft corrections can then be combined with contributions arising from the exchange of potential photons to obtain the complete $\mathcal{O}({\alpha }^{2}Z)$ correction to the decay rate, with resummation of large logarithms of the electron energy times the nuclear radius. We find that $\mathcal{O}({\alpha }^{2}Z)$ ultrasoft loops induce a relative correction to the decay rate that ranges from $0.7\cdot 10^{-3}$ in the decay of ${}^{10}$C to $3.6\cdot 10^{-3}$ in the decay of ${}^{54}$Co, and will thus impact the extraction of $V_{ud}$ at the permille level. We show that the inclusion of these corrections reduces the residual renormalization scale dependence of the decay rate to a negligible level, making missing ultrasoft perturbative corrections a subdominant source of theoretical error.

   ↳ hep-phhep-exnucl-exnucl-thJHEP(2026)·10 citations
7. 07*

   Transmission Efficiency of the Recoil Mass Spectrometer EMMA at TRIUMF

   B. Davids🇨🇦 · N.E. Esker🇺🇸 · J. Jaeyoung · Y.K. Kim · K. Pak · M. Williams🇺🇸

   The mean transmission efficiency of the EMMA recoil mass spectrometer at TRIUMF has been measured with 6 different angular apertures at 17 kinetic energy/charge deviations with respect to the central, reference trajectory. Measurements performed using a 148Gd alpha source installed at the target position of the spectrometer are compared to ion-optical calculations and Monte Carlo simulations. The transmission efficiency as a function of angle and kinetic energy/charge is described empirically using piecewise Gaussian functions whose parameters are fit to the data.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2026)·0 citations
8. 08*

   Jet fragmentation function and groomed substructure of bottom quark jets in proton-proton collisions at 5.02 TeV

   CMS Collaboration

   A measurement of the substructure of bottom quark jets (b jets) in proton-proton (pp) collisions is presented. The measurement uses data collected in pp collisions at $\sqrt{s}$ = 5.02 TeV, with a low number of simultaneous interactions per bunch crossing, recorded by the CMS experiment in 2017, corresponding to an integrated luminosity of 301 pb${}^{-1}$. An algorithm to identify and cluster the charged decay daughters of b hadrons is developed for this analysis, which facilitates the exposure of the gluon radiation pattern of b jets using iterative Cambridge$-$Aachen declustering. The soft-drop-groomed jet radius, $R_{\mathrm{g}}$, and momentum balance, $z_{\mathrm{g}}$, of b quark jets are presented. These observables can be used to test perturbative quantum chromodynamics predictions that account for mass effects. Because the b hadron is partially reconstructed from its charged decay daughters, only charged particles are used for the jet substructure studies. In addition, a jet fragmentation function, $z_{\text{b,ch}}$, is measured, which is defined as the distribution of the ratio of the transverse momentum ($p_{\mathrm{T}}$) of the partially reconstructed b hadron with respect to the charged-particle component of the jet $p_{\mathrm{T}}$. The substructure variable distributions are unfolded to the charged-particle level. The b jet substructure is compared to the substructure of jets in an inclusive jet sample that is dominated by light-quark and gluon jets in order to assess the role of the b quark mass. A strong suppression of emissions at small $R_{\mathrm{g}}$ values is observed for b jets when compared to inclusive jets, consistent with the dead-cone effect. The measurement is also compared with theoretical predictions from Monte Carlo event generators. This is the first substructure measurement of b jets that clusters together the b hadron decay daughters.

   ↳ hep-exnucl-exJHEP(2026)·6 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.