Nuclear Experiment·nucl-ex

Tue·Jun 16, 2026Tuesday·June 16, 2026

10 papers—3 primary·7 cross-listed

01
Experimental exploration of the QCD phase diagram
A. Andronic🇩🇪 · P. Braun-Munzinger🇩🇪 · K. Redlich🇵🇱 · J. Stachel🇩🇪
The different phases of strongly interacting matter are governed by Quantum Chromodynamics (QCD). At high temperature and/or density a deconfined, chirally symmetric phase of quarks and gluons is expected to govern the nature of strongly interacting matter, the so-called quark-gluon plasma. Here we review what is known about the existence of this exotic form of matter from an experimental point of view and confront the results with QCD predictions based on 'Lattice QCD', where QCD is discretized on a space-time lattice and solved numerically in a Monte Carlo approach. The form of the presentation is explicitly pedagogical but the results include even very recent developments. Our research is based on the interpretation of hadron production data from relativistic nucleus--nucleus collisions over a wide energy range, with the aim to make progress in the understanding of the QCD phase, and of phenomena like deconfinement and hadronization.
nucl-exhep-phnucl-th0 citations
02
Evidence for a $K ˉ N N$ quasi-bound state in the $γ d \to K^{0} Λ p$ reaction
R. Kobayakawa🇯🇵 · J. K. Ahn🇰🇷 · S. Ajimura🇯🇵 · W.-C. Chang🇹🇼 · M.-L. Chu🇹🇼 · S. Daté🇯🇵 · T. Gogami🇯🇵 · T. A. Hashimoto🇯🇵 · T. Hotta🇯🇵 · T. Ishikawa🇯🇵 · H. Katsuragawa🇯🇵 · H. Kohri🇯🇵 and 25 other authors
The $γ d \to K^{0} Λ p$ reaction has been studied to search for a $K ˉ N N$ quasi-bound state using the LEPS2 solenoid spectrometer at SPring-8. A localized enhancement concentrated at low $q$ is observed in the $(M_{Λ p}, q)$ distribution below the $K^{-} pp$ mass threshold, where $M_{Λ p}$ is the $Λ p$ invariant mass and $q \equiv ∣ p_{γ} - p_{K^{0}} ∣ = ∣ p_{Λ p} ∣$ is the momentum transfer. A two-dimensional $(M_{Λ p}, q)$ fit demonstrates that the enhancement near the threshold is statistically significant, yielding a local significance of $7.3, σ$ . The enhancement is characterized by effective shape parameters including the Breit--Wigner mass $M$ and width $Γ$ , and a Gaussian form-factor momentum scale $Q$ : $M = 2.354 \pm 0.011 (stat.)_{- 0.005}^{+ 0.009} (syst.) GeV / c^{2}$ , $Γ = 0.055 \pm 0.023 (stat.)_{- 0.009}^{+ 0.031} (syst.) GeV / c^{2}$ , and $Q = 0.350 \pm 0.041 (stat.)_{- 0.010}^{+ 0.035} (syst.) GeV / c$ . The obtained results support the existence of a $K ˉ N N$ quasi-bound state in photoproduction.
nucl-exPLB(2026)·0 citations
03
CBM physics program and recent experimental developments
CBM Collaboration
The Compressed Baryonic Matter (CBM) fixed-target experiment is under construction at the Facility for Antiproton and Ion Research. It aims to explore the phase structure of strong interaction (QCD) matter at high net-baryon densities and moderate temperatures using heavy-ion collisions in the center-of-mass energy range per nucleon pair $s_{NN} =$ 2.7--4.9\,GeV. Equipped with fast and radiation-hard detector systems and an advanced triggerless data acquisition scheme, CBM will collect data at interaction rates of up to 10 MHz by performing online reconstruction and event selection. This will facilitate measurements of rare probes not accessible so far in this energy range, including multi-strange hadron production and their flow coefficients, high-order net-baryon cumulants, dileptons, as well as production of double-strange hypernuclei. The CBM detector is outlined and selected physics performance results based on realistic simulations are discussed.
nucl-ex0 citations
04
Peak-Based Nuclide Identification in HPGe $γ$ -Spectrometry with Machine Learning and SHAP
Samuel Emmons · Kelly Truax · Maurice Lonsway · Bruce Pierson🇺🇸 · Brian Archambault🇺🇸
High-purity germanium gamma spectra often require time-consuming analyses from subject matter experts. Photopeaks within these spectra are carefully fitted and numerical methods are employed to assist with nuclide identification (NID) and quantification. Amending the list of nuclides identified by analysis software can be nontrivial. When many samples need to be analyzed, it is therefore challenging to make timely and correct decisions. Supervised machine-learning-based NID can serve as an expert-informed, automated tool to improve the initial set of radionuclides suggested to an analyst and more effectively drive subsequent quantification. To that end, we implemented machine learning models that map photopeaks carefully fitted by analysts to NID results for experimental spectra containing various isotopic combinations drawn from a set of 65 isotopes. The best model achieved an F1 score of 0.97, markedly surpassing the F1 score of 0.84 achieved by traditional software when compared using a nuclide library comprising the same 65 isotopes assessed by the models. Finally, we illustrated the most important input features for model predictions using Shapley Additive Explanations. These explanations revealed that the models use physically relevant photopeaks when making predictions for the isotopes in our nuclide library.
↳ physics.data-ancs.LGnucl-ex0 citations
05
Fast-reactor neutron sources in evaluated nuclear data library validation
Aaron Hurst · Emanuel Chimanski🇺🇸 · Toshihiko Kawano🇺🇸 · David Brown · David Matters · Lee Bernstein
Two different neutron sources, based on $^{235}$ U-fission neutrons with different average energies, provide integral benchmark data for validation of $γ$ -ray production data in the evaluated nuclear data libraries corresponding to fast-neutron-induced inelastic-neutron scattering reactions. Firstly, we consider the IRT-M Research Reactor, formerly located at the Nuclear Research Institute just outside of Baghdad, Iraq, to demonstrate the validation methodology using the associated $γ$ -ray data in the Evaluated Nuclear Data File, version VIII.0 (ENDF/B-VIII.0), for several $γ$ -ray transitions over a wide range of nuclides including $^{28}$ Si, $^{32}$ S, $^{56}$ Fe, and $^{186}$ W. Using the characterized neutron flux of the Baghdad IRT-M Reactor, we find flux-weighted cross-sections deduced using the ENDF/B-VIII.0 $γ$ -ray data to be in good agreement with the integral measurements performed at the Baghdad Research Reactor in addition to the corresponding results of different reaction-model calculations, {\tt CoH $_{3}$ } and {\tt EMPIRE}. Given the excitation thresholds for the $γ$ -ray transitions involved in this investigation, these observations lend further support to the characterization of the IRT-M flux in the fast-neutron energy region $0.862 \leq E_{n} \leq 5.0$ MeV. The additional detail devoted to the IRT-M source reflects the broader scope of the validation work carried out at that facility. A second neutron source considered for this validation work is the Forschungsreaktor Münich (FRM-II), Garching, Germany. Again, the flux-weighted $γ$ -ray data from ENDF/B-VIII.0 for $^{56}$ Fe compare well to the integral FRM-II measurement and reaction-model calculations.
↳ nucl-thnucl-ex0 citations
06
Production of high-orbital kaon excited states in the $K^{-} p$ reaction
Ting-Yan Li🇨🇳 · Zi-Yue Bai🇨🇳 · Xiang Liu🇨🇳
In this work, a systematic investigation of the production of high-orbital-excitation kaons in $K^{-} p$ reactions is carried out within an effective Lagrangian approach. The relevant $t$ -channel processes are constructed, and the model is calibrated using a single adjustable parameter determined from existing experimental data. With this parameter, the measured production cross sections for the $K_{3}^{*} (1780)$ , $K_{2} (1820)$ , $K_{2} (1770)$ and $K_{4}^{*} (2045)$ states are successfully reproduced. Employing the same framework, the production cross sections for other high-orbital kaons are predicted. The results indicate that these states possess sizable cross sections and exhibit characteristically forward-peaked angular distributions, which is a typical feature of $t$ -channel exchange, highlighting their great potential for observation in future experiments.
↳ hep-phhep-exnucl-exnucl-thPRD(2026)·0 citations
07
GPT-Based Fast Simulation of CLAS12 Detector Hits via Conditional Autoregressive Generation
Cole Granger🇺🇸 · James Giroux🇺🇸 · Richard Tyson🇬🇧 · Maurizio Ungaro🇺🇸 · Cristiano Fanelli🇺🇸
Modern particles physics experiments have demonstrated an increasing need for fast, high-fidelity detector simulation as detector components have improved and subsequent computational requirements approach the limits of available resources. Recently, deep generative models have emerged as a promising alternative to traditional Monte-Carlo methods, with recent works drawing inspiration from large language models (LLMs) and self-supervised next-token prediction methods. In this work, we present an application of a GPT-style autoregressive transformer as a fast surrogate model for the calorimeter inside the CLAS12 experiment at the Thomas Jefferson National Accelerator Facility. The model is conditioned on incident momentum and generates realistic detector hits autoregressively across all nine calorimeter layers as sequences of strip, ADC, and TDC tokens. We demonstrate that the model faithfully reproduces hit multiplicity, spatial distributions, energy deposits, and the energy-momentum response of the electromagnetic calorimeter. The generator achieves inference rates exceeding 700 events per second on a single GPU, providing a substantial speedup over traditional Geant4-based simulations while maintaining physics fidelity essential for high-luminosity experimental programs.
↳ physics.ins-detcs.LGhep-exnucl-ex+11 citation
08
Studies of Neutrino-Nucleus Elastic Scattering with Point-Contact Germanium Detectors at the Kuo-Sheng Reactor Neutrino Laboratory
TEXONO Collaboration · M.K. Singh · S. Karmakar · Greeshma C. · H.B. Li · F.K. Lin · V. Sharma · L. Singh · H.T. Wong · L.T. Yang · M. Agartioglu · J.H. Chen and 27 other authors
The low energy and intense flux of electron anti-neutrinos from nuclear reactors provide the perfect stage to study elastic neutrino-nucleus scattering ( $ν A_{e l}$ ) in the fully coherent regime. We report results from the TEXONO experiment using electro-cooled $p$ -type point-contact Germanium detectors with masses of 523~g and 1434~g at the Kuo-Sheng Reactor Neutrino Laboratory. We report improved constraints on the $ν A_{e l}$ cross section with a combined exposure of 404(813.7)~kg-days of Reactor ON(OFF) data at an electron-equivalent threshold of 200~eV $_{ee}$ . The Lindhard model, in which the quenching factor is parameterized by a single parameter k, is adopted to describe the suppression of ionization yield. At the benchmark value of k=0.162, a limit of $ρ <$ 2.0 at 90\% confidence level (CL) is derived, where $ρ$ represents the ratio of the observed to the predicted Standard Model cross section. Moreover the region k $>$ 0.205 is excluded at 90\% CL using the SM-predicted $ν A_{e l}$ rate. A bound on the neutrino magnetic moment from $ν A_{e l}$ at $μ_{ν} < 5.9 \times 1 0^{- 10} μ_{B}$ at 90\% CL is also derived.
↳ hep-exnucl-exphysics.ins-det1 citation
09
Spin-Selective Hadron Spectroscopy via Azimuthal Anisotropies from Entanglement-Enabled Spin Interference
Samuel Corey🇺🇸 · James Daniel Brandenburg🇺🇸
The $π^{+} π^{-}$ invariant mass spectrum above the $ρ^{0} (770)$ is rich with broad, overlapping resonances. Disentangling them, whether in photoproduction, ultra-peripheral heavy-ion collisions, or electroproduction, is a longstanding challenge for conventional partial-wave analysis. We show that the recently observed entanglement-enabled spin-interference effect in ultra-peripheral collisions provides a quantum-mechanical filter that resolves this ambiguity: the angular harmonics $A_{n}$ of the $cos (n Δ ϕ)$ asymmetry, which are governed by selection rules in the spin of the interfering states. Specifically, overlap between two distinct spin-1 amplitudes leads to interference that populate $A_{2}$ alone, while overlap of a spin-1 amplitude with a spin-2 one generates $A_{1}$ and $A_{3}$ . Utilizing ALICE data in the $1.0$ -- $1.4 GeV c^{- 2}$ region, we demonstrate that two physically distinct hypotheses -- an additional spin-1 $ρ^{'} (1450)$ (produced via photonuclear interactions) versus a spin-2 (photon-photon) $f_{2} (1270)$ state -- fit the invariant mass spectrum equally well but predict different $A_{n}$ : identically zero $A_{1}$ and $A_{3}$ in the spin-1 case, versus pronounced peaks in the spin-2 case. This selection rule provides a new tool for hadronic spectroscopy in ultra-peripheral collisions and the first viable route to isolating the $γ γ \to π^{+} π^{-}$ continuum from the dominant photonuclear background, revealing a clean low-energy probe of non-perturbative QCD.
↳ hep-phnucl-exnucl-th0 citations
10
First Experimental Limit on the Thermal Solar Neutrino Flux
Cecilia Ferrari🇺🇸 · Gonzalo Herrera🇺🇸 · Brooke Russell🇺🇸
The neutrino sky below 165\,keV is yet to be explored. This region provides a unique probe of stellar cooling mechanisms through the detection of thermal solar neutrinos and the low-energy tail of the $pp$ solar cycle. Here, we investigate prospects for probing this regime via neutrino capture on tritium. Analyzing KATRIN public data, we set the first experimental bound on the thermal solar neutrino flux $Φ/ Φ_{SSM} < 1.86 \times 1 0^{18}$ at 95\%~CL ( $1.58 \times 1 0^{18}$ at 90\%~CL), and show that a $100 kg \cdot yr$ exposure would constrain the thermal solar neutrino component to $Φ/ Φ_{SSM} ≲ 1 0^{4}$ and detect the low-energy $pp$ flux at the Standard Solar Model (SSM) level. Neutrino--electron elastic scattering from $pp$ cycle neutrinos are identified as an irreducible background for neutrino capture searches.
↳ hep-phhep-exnucl-ex1 citation

Affiliations

first authorsco-authorsvia INSPIRE