Fri·Nov 14, 2025Friday·November 14, 2025

1. 01*

   Reducing Systematic Bias in Machine Learning Applications to Signal Extraction in High-Energy Nuclear Physics

   Yan Wang🇨🇳 · Rangrong Ma🇺🇸 · Kaifeng Shen🇨🇳 · Zebo Tang🇨🇳 · Wangmei Zha🇨🇳

   Machine learning techniques are increasingly being applied in high-energy nuclear physics data analysis thanks to their outstanding performance. One key challenge in such applications is the construction of training samples that can accurately represent real data. Training samples are typically generated through detector simulations, but discrepancies between simulated and real data can lead to degradation in machine learning performance and systematic biases in the results. This paper introduces two methods: i) cumulative distribution function mapping and ii) shift-and-scale, to align simulated signals with real data, which can aid in eliminating the aforementioned issues. We use the J/$\psi$ yield measurement in 200 GeV Ru+Ru and Zr+Zr collisions with the STAR experiment as an example to demonstrate the application and effectiveness of the proposed methods.

   nucl-exhep-exNucl.Sci.Tech.(2026)·1 citation
2. 02*

   Strangeness production as a function of charged-particle multiplicity in proton-proton collisions at $\sqrt{\mathbf{s}}=5.02$ TeV

   ALICE Collaboration

   (Multi-)strange particle production rates and transverse momentum distributions are measured at midrapidity ($|y|<0.5$) as a function of the charged-particle multiplicity density by the ALICE experiment at the LHC, using proton-proton collisions at a center-of-mass energy of $\sqrt{\mathbf{s}}=5.02$~TeV. This study extends similar studies performed at $\sqrt{\mathbf{s}}=7$~TeV and $\sqrt{\mathbf{s}}=13$~TeV to a lower energy regime, improving the statistical precision and extending the measurement to previously unexplored low-multiplicity regions. While $K_S^0$, $\Lambda$, and $\Xi$ yields can be described with a linear multiplicity dependence within uncertainties, the $\Omega$ yields follow a significantly faster than linear increasing trend. For all analyzed particles, the overall production rate is consistent with those observed at higher energy and at similar multiplicity densities. Transverse momentum distributions are observed to evolve with multiplicity. Several state-of-the-art QCD-inspired Monte Carlo models have been compared to the data, testing some recently introduced features to address the findings at higher energies. Models can qualitatively describe the transverse momentum spectra and the $\Lambda /K_S^0$ spectral ratio only if collectivity is introduced in the evolution of the system.

   nucl-exPRC(2026)·7 citations
3. 03*

   Energy Levels of 15Be

   K. Setoodehnia🇺🇸 · J. H. Kelley

   In this document, experimental nuclear structure data are evaluated for 15Be. The details of each reaction populating 15Be levels are compiled and evaluated. The combined results provide a set of adopted values that include level energies, spins and parities, level widths, decay types and other nuclear properties.

   nucl-ex0 citations
4. 04*

   Energy Levels of 16Be

   K. Setoodehnia🇺🇸 · J. H. Kelley

   In this document, experimental nuclear structure data are evaluated for 16Be. The details of each reaction populating 16Be levels are compiled and evaluated. The combined results provide a set of adopted values that include level energies, spins and parities, level widths, decay types and other nuclear properties.

   nucl-ex0 citations
5. 05*

   Centrality dependence of strange particle production in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV

   ALICE Collaboration

   The centrality dependence of strange ($K_S^0$, $\Lambda +\bar{\Lambda }$) and multi-strange (${\Xi }^{-}+\overline{{\Xi }^{+}}$, ${\Omega }^{-}+{\bar{\Omega }}^{+}$) hadron production is measured by ALICE in the LHC lead-lead (Pb-Pb) collisions at a center-of-mass energy per nucleon pair $\sqrt{s_{\mathrm{NN}}}=5.02$~TeV, using the full data set collected during the LHC Run 2 campaign in the years 2015 and 2018. This is the largest heavy-ion data set analyzed to date at the LHC, and it allows for the extraction of transverse momentum ($p_T$) spectra and $p_T$-integrated yields with unprecedented precision, over a broad range of charged particle multiplicity densities ($⟨d{N}_{ch}/d\eta {⟩}_{|\eta |<0.5}$), probing regions where smaller collision system (pp and p-Pb) results are also available. The $p_T$ spectra evolve with centrality, featuring higher $⟨p_T⟩$ in central events for all particles. The $\Lambda /K_S^0$ ratio exhibits the distinctive baryon-to-meson enhancement in the intermediate $p_T$ region, with a maximum which is shifted to larger $p_T$ for more central collisions. The hadron-to-pion yield ratios are presented as a function of $⟨d{N}_{ch}/d\eta {⟩}_{|\eta |<0.5}$ and compared to results from different collision systems and energies. A smooth connection from pp to Pb-Pb is observed, thus demonstrating that collision system or energy do not play a role in the multiplicity evolution of this observable. The previously reported enhancement of strangeness production in the multiplicity range probed in pp and p_Pb collisions saturates in the multiplicity range of Pb-Pb data. These results constitute a key test bench for theoretical models and a first comparison to the EPOS~4 generator is presented.

   nucl-exPRC(2026)·9 citations
6. 06*

   Multiplicity dependence of two-particle angular correlations of identified particles in pp collisions at $\sqrt{\mathbf{s}}=13$ TeV

   ALICE Collaboration

   Two-particle angular correlations explore particle production mechanisms and underlying event-wide phenomena present in the systems created in hadronic collisions. These correlations are examined as a function of rapidity and azimuthal-angle differences ($\Delta y,\Delta \phi$) for pairs of like- and unlike-sign pions, kaons, and (anti-)protons produced in pp collisions at $\sqrt{s}$ = 13 TeV, measured by the ALICE experiment. Two-particle correlation functions are provided, along with $\Delta y$ and $\Delta \phi$ projections, and are compared to Monte Carlo (MC) model predictions. For the first time, the measurement is performed as a function of the event's charged-particle density. The shapes of the correlation functions are studied in detail for each particle pair. Previous studies conducted for pp collisions at $\sqrt{s}$ = 7 TeV at ALICE have revealed an anticorrelation at small relative angles for baryon-baryon and antibaryon-antibaryon pairs, whose origin remains an open question. In this work, an additional approach is introduced to study the multiplicity dependence of the correlation functions in more detail and reveal qualitative differences in the underlying sources of correlations, such as quantum statistics, final-state interactions, and resonance decays. The puzzling near-side anticorrelation in baryon-baryon measurements is observed across all multiplicity classes and remains a challenge for models of particle production in pp collisions. Furthermore, the multiplicity dependence of the correlations between mesons provides an independent means to explore the sensitivity of current MC models to soft-QCD effects and hadronization dynamics. The presented measurements, together with the baryon results, enrich the experimental picture of two-particle correlations in pp collisions and serve as valuable input for ongoing theoretical developments.

   nucl-exhep-exEPJC(2026)·1 citation
7. 07*

   Strangeness enhancement at its extremes: multiple (multi-)strange hadron production in pp collisions at $\sqrt{\text{s}}=5.02$ TeV

   ALICE Collaboration

   The probability to observe a specific number of strange and multi-strange hadrons ($n_s$), denoted as $P(n_s)$, is measured by ALICE at midrapidity ($|y|<0.5$) in $\sqrt{s}=5.02$ TeV proton-proton (pp) collisions, dividing events into several multiplicity-density classes. Exploiting a novel technique based on counting the number of strange-particle candidates event-by-event, this measurement allows one to extend the study of strangeness production beyond the mean of the distribution. This constitutes a new test bench for production mechanisms, probing events with a large imbalance between strange and non-strange content. The analysis of a large-statistics data sample makes it possible to extract $P(n_s)$ up to a maximum $n_s$ of 7 for K${}_{\mathrm{s}}^0$, 5 for $\Lambda$ and $\bar{\Lambda }$, 4 for ${\Xi }^{-}$ and ${\Xi }^{+}$, and 2 for ${\Omega }^{-}$ and ${\Omega }^{+}$. From this, the probability of producing strange hadron multiplets per event is calculated, thereby enabling the extension of the study of strangeness enhancement to extreme situations where several strange quarks hadronize in a single event at midrapidity. Moreover, comparing hadron combinations with different $u$ and $d$ quark compositions and equal overall $s$ quark content, the contribution to the enhancement pattern coming from non-strangeness related mechanisms is isolated. The results are compared with state-of-the-art phenomenological models implemented in commonly used Monte Carlo event generators, including PYTHIA 8 Monash 2013, PYTHIA 8 with QCD-based Color Reconnection and Rope Hadronization (QCD-CR + Ropes), and EPOS LHC, which incorporates both partonic interactions and hydrodynamic evolution. These comparisons show that the new approach dramatically enhances the sensitivity to the different underlying physics mechanisms modeled by each generator.

   nucl-exhep-exJHEP(2026)·7 citations
8. 08*

   Probing jet hadrochemistry modification with measurements of $\pi$, K, and p in jets and the underlying event in pp and Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV

   Sierra Cantway (for the ALICE Collaboration)🇺🇸

   Measurements of jet substructure observables in heavy-ion (HI) collisions provide powerful constraints on the microscopic mechanisms of interactions between energetic partons and the quark--gluon plasma (QGP). Although there has been remarkable progress in measuring inclusive jet substructure, a complete understanding of identified particle production inside jets (jet hadrochemistry) and its modification in HI collisions remains elusive. Jet quenching models predict that the jet hadrochemical composition is modified in the QGP, arising from both jet-medium interactions and altered particle production in the jet wake. Measurements of jet hadrochemistry can help discriminate between proposed jet-medium interaction mechanisms. Enabled by the excellent particle identification (PID) capabilities of ALICE, we present the first measurements of $\pi$, K, and p ratios within jets and the underlying event as a function of particle transverse momentum in pp and Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV. These measurements provide insight into soft particle production mechanisms and helps distinguish various jet quenching effects.

   nucl-exEPJ Web Conf.(2026)·1 citation
9. 09*

   Topmetal-L: A Low Noise Charge-Sensitive Pixel Sensor for POLAR2/LPD

   Li-rong Xie · Shi-Qiang Zhou · Di-Fan Yi · Huan-Bo Feng · Zhu-Ke Feng · Dong Wang🇨🇳 · Chao-song Gao🇨🇳 · En-Wei Liang🇨🇳 · Xiang-Ming Sun🇨🇳 · Hong-Bang Liu🇨🇳

   POLAR-2 is a next-generation space astronomy platform led by China, with its core scientific objective focused on high-precision polarization measurements of gamma-ray bursts. As one of its key payloads, the Low-energy Polarization Detector (LPD) is designed to perform wide-field surveys to capture X-ray polarization information from gamma-ray bursts in the 2$\sim$10 keV energy range. This paper presents Topmetal-L, a dedicated charge-sensitive pixel sensor developed for the LPD prototype upgrade. Fabricated in a 130 nm CMOS process in 2024, the chip integrates a 356 $\times$ 512 pixel array with a pixel pitch of 45 $\mu$m. Each pixel incorporates a 26 $\times$ 26 $\mu$m${}^2$ charge-collecting window and is capable of simultaneously outputting both energy and position information of deposited charges. Topmetal-L has been systematically optimized for power consumption, noise performance, and readout efficiency. It exhibits an input dynamic range of 0$\sim$4 ke${}^{-}$, a typical charge-to-voltage conversion gain of 76.04 $\mu$V/e${}^{-}$, an average equivalent noise charge of approximately 22.8 e${}^{-}$, a sensitive area exceeding 3.69 cm${}^2$, and a total power consumption of 720 mW per chip. To meet the requirements of large-area, high-frame-rate readout for gas-based polarization detectors, a sentinel readout scheme is proposed, reducing the full-frame readout time to 730 $\mu$s. A prototype Topmetal-L-based gas polarization detection system was evaluated across key energies: it exhibited a residual modulation of 0.26% $\pm$ 0.45% at 5.90 keV, a modulation factor of 66.67% $\pm$ 0.45% for a linearly polarized 8.05 keV source, and a count rate saturated at 15 k counts$\cdot$cm${}^{-2}$$\cdot$s${}^{-1}$ when tested at 5.40 keV.

   ↳ astro-ph.IMnucl-exphysics.ins-det4 citations
10. 10*

    Radii of proton emitters

    Y. R. Lin🇨🇳 · S. M. Wang🇨🇳 · W. Nazarewicz🇺🇸

    Nuclear radius is a fundamental structural observable that informs many properties of atomic nuclei and nuclear matter. Experimental studies of radii in drip line nuclei are in the forefront of research with radioactive ion beams. Of particular interest are charge radii of proton-unbound nuclei that will soon be approached in laser spectroscopy. In this Letter, using the complex-energy approach and direct time propagation, we investigate the radius of the proton resonance whose size is ill defined in the standard stationary quantum-mechanical description. An early-time plateau is identified during which the radius of the Gamow resonance coincides with the real-energy radius accessible experimentally. We demonstrate a nonmonotonic dependence of the complex radius on decay energy and a local increase of the charge radius across the threshold (a halolike enhancement).

    ↳ nucl-thnucl-exPRL(2026)·2 citations
11. 11*

    Time resolution of the ALICE Time-Of-Flight detector with the first Run 3 pp collisions at $\sqrt{\text{s}}=13.6$ TeV

    ALICE Collaboration

    Particle identification (PID) is a fundamental aspect of the ALICE detector system, central to its heavy-ion and proton-proton physics programs. Among the different PID strategies, ALICE uses the Time-Of-Flight (TOF) detector to identify particles at intermediate momenta ($0.5<p_{\mathrm{T}}<4$ GeV/$c$). The ALICE TOF detector performed successfully during the first ten years of LHC operations. During the Long Shutdown 2, many ALICE sub-detectors, including TOF, were upgraded to fully leverage the targeted 50 kHz interaction rate of Pb-Pb collisions, which required the implementation of a continuous readout scheme. The TOF detector electronics were upgraded and refurbished, while processing algorithms for data quality control, reconstruction, calibration, and analysis were rewritten. This paper presents the upgraded TOF detector operation and calibration procedures and its performance in terms of timing resolution, a key factor for particle separation in ALICE analyses. Using 2022 pp collision data at $\sqrt{s}=13.6$ TeV from Run 3, the time resolution of the detector was estimated with two independent methods, both yielding consistent results, better than 80 ps. Despite the excellent performance already achieved, further improvements are expected after additional detector commissioning and refined calibration procedures, thus enhancing the ALICE PID capabilities for Run 3 and beyond.

    ↳ physics.ins-dethep-exnucl-exEur.Phys.J.Plus(2026)·3 citations
12. 12*

    Emulation of Proton-Deuteron Scattering via the Reduced Basis Method and Active Learning: Detailed Description

    Alex Gnech🇺🇸 · Xilin Zhang🇺🇸 · Christian Drischler🇺🇸 · R. J. Furnstahl🇺🇸 · Alessandro Grassi🇮🇹 · Alejandro Kievsky🇮🇹 · Laura E. Marcucci🇮🇹 · Michele Viviani🇮🇹

    Nucleon-deuteron ($Nd$) scattering can be used to constrain three-nucleon forces in chiral effective field theory ($\chi$EFT). However, high-fidelity calculations, such as the Hyperspherical Harmonic (HH) method, are computationally expensive, making it difficult or even prohibitive to explore the vast parameter space of $\chi$EFT\xspace. To address this challenge, specifically for proton-deuteron ($pd$) scattering below the deuteron breakup threshold, we developed model-driven emulators based on the Reduced Basis Method (RBM) and active learning techniques, as presented in \href{https://arxiv.org/abs/2511.01844}{arXiv:2511.01844}. The method exploits the similarities between solutions at different parameter points to significantly reduce computational costs. In this companion paper, we provide a comprehensive description of our HH-based high-fidelity calculations and implementation of both variational-method-based and Galerkin-projection-based scattering emulators. We demonstrate the effectiveness of active learning in the form of greedy algorithms for selecting optimal training points in the parameter space, and the high accuracy and speed of the emulators, for two different nucleon forces and two scattering channels (${1/2}^{+}$ and ${1/2}^{-}$). For example, in a two-dimensional parameter space, the relative emulation errors can be reduced to $10^{-7}$ with fewer than 10 training points. Our work paves the way for the efficient calibration of $\chi$EFT\xspace nucleon interactions using Bayesian statistics, and the methodology can be applied to other nuclear scattering processes (including neutron-deuteron scattering), as well as other finite quantum systems.

    ↳ nucl-thhep-phnucl-ex6 citations
13. 13*

    Friction terms in multi-fluid description of heavy-ion collisions

    Clemens Werthmann🇧🇪 · Iurii Karpenko🇨🇿 · Pasi Huovinen🇵🇱

    In multi-fluid description of heavy-ion collisions, the primary scatterings and particle production are described in terms of interaction between fluids, so called friction. These friction terms can be derived from kinetic theory, but they are not unique. We compare different approaches to derive the friction terms, introduce a new ``charge transfer" friction, which allows to move charge to the midrapidity fireball, and implement them in the MUFFIN model. The charge transfer friction is more consistent with the assumption of three fluids clearly separated in momentum space, and allows better comparisons of the experimental data and underlying equation of state. It also leaves room for entropy generation due to dissipation in individual fluids, and we present the first results obtained using viscous multi-fluid dynamics.

    ↳ nucl-thhep-phnucl-exPRC(2026)·2 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.