Fri·Nov 7, 2025Friday·November 7, 2025

1. 01*

   Validating a Machine Learning Approach to Identify Quenched Jets in Heavy-Ion Collisions

   Yilun Wu🇨🇳 · Yi Chen🇺🇸 · Julia Velkovska🇺🇸

   Jet quenching is a phenomenon in heavy-ion collisions arising from jet interactions with the quark-gluon plasma (QGP). Its study is complicated by the interplay of multiple physics processes that affect jet observables. In addition, detector effects may influence the results and must be accounted for when identifying quenched jets. We employ a Long Short-Term Memory (LSTM) neural network trained on jet substructure, incorporating parton shower history, to predict jet-by-jet quenching levels. Using photon-jet samples from the \textsc{Jewel} event generator, we show that the LSTM predictions strongly correlate with true jet energy loss. This validates that the model effectively learns the features of jet-QGP interaction. We simulate detector effects using \textsc{Delphes} simulation framework and demonstrate that the method identifies quenching effects in a realistic environment. We test the approach with photon-jet momentum imbalance, jet fragmentation function, and jet shape, which were not included in the training, confirming its ability to distinguish true quenching features.

   ↳ hep-phnucl-exJHEP(2026)·1 citation
2. 02*

   Predictions of baryon directed flow in heavy-ion collisions at high baryon density

   Yuri B. Ivanov🇷🇺

   Predictions of the proton directed flow ($v_1$) in semicentral Au+Au collisions in the energy range between 4.5 and 7.7 GeV are done. The calculations are performed within the model of three-fluid dynamics with crossover equation of state, which well reproduces the proton $v_1$ both below 4.5 GeV and above 7.7 GeV, as well as bulk observables in the energy range of interest. It is predicted that the proton flow evolves non-monotonously. At the energy of 7.2 GeV it exhibits antiflow (i.e. negative slope of $v_1(y)$) in the midrapidity. At 7.7 GeV, the flow returns to the normal pattern in accordance with the STAR data. The midrapidity $v_1$-slope excitation functions within the first-order phase and crossover transitions to quark-gluon phase (QGP) turn out to be qualitatively similar, but the amplitude of the wiggle in the crossover scenario is much smaller than that in the strong first-order phase transition. Therefore, the change of sign followed by minimum at 7.2 GeV in the $v_1$-slope excitation function indicates onset of (weak phase or crossover) transition to QGP. The second change of the sign around 10 GeV results from interplay between incomplete baryon stopping and transverse expansion of the system.

   ↳ nucl-thhep-phnucl-exPRC(2026)·1 citation
3. 03*

   Exclusive photoproduction of a di-meson pair with large invariant mass

   Saad Nabeebaccus🇬🇧 · David Perez🇫🇷 · Lech Szymanowski🇵🇱 · Samuel Wallon🇫🇷

   We consider the exclusive photoproduction of a di-meson pair with large invariant mass, $\gamma N\to N^{\prime }{M}_1{M}_2$, in the framework of collinear factorisation. The mesons considered $M_1$ and $M_2$ are either pions or rho mesons, charged or neutral. We consider the kinematic regime characterised by a large invariant mass of the two-meson system, and a small deflection of the nucleon in the centre-of-mass frame. In this kinematic domain, the amplitude factorises into a perturbative hard part and non-perturbative parts described by Generalised Parton Distributions (GPDs) and Distribution Amplitudes (DAs). We automate the calculation of the fully differential cross section at leading twist and leading order, and we present some numerical results at JLab 12 GeV kinematics. This class of processes provides yet more exclusive $2\to 3$ channels that can be used to extract GPDs.

   ↳ hep-phhep-exnucl-exnucl-th1 citation
4. 04*

   The size of the quark-gluon plasma in ultracentral collisions: impact of initial density fluctuations on the average transverse momentum

   Fabian Zhou🇩🇪 · Giuliano Giacalone🇨🇭 · Jean-Yves Ollitrault🇫🇷

   Recent experiments have shown that the mean transverse momentum $⟨p_T⟩$ of outgoing particles increases as a function of the particle multiplicity in ultracentral nucleus-nucleus collisions at collider energies. This increase was originally predicted on the basis of simulations where the multiplicity increase occurred at constant volume, so that it implied a larger density and temperature. However, recent state-of-the-art simulations have shown that, for some models of initial condition, the volume may vary with the multiplicity in ultracentral collisions. We elucidate this effect by analytically relating the variation of the volume to the radial distribution of the one- and two-point functions of the fluctuating density field. We show that the volume variation is small if the total entropy of the ultracentral collisions scales with the mass number of the colliding isotopes. We argue that probing detailed transverse distributions of initial-state fluctuations through the ultracentral $⟨p_T⟩$ has nontrivial implications for models of nuclear structure and of the pre-equilibrium stages.

   ↳ nucl-thhep-phnucl-exPRC(2026)·4 citations
5. 05*

   A prototype neutron-detector array for future deep-underground s-process studies

   Thomas Chillery🇮🇹 · David Rapagnani🇮🇹 · Chemseddine Ananna🇮🇹 · Edoardo D'Amore🇮🇹 · Gianluca Imbriani🇮🇹 · Antonino di Leva🇮🇹 · Daniela Mercogliano🇮🇹 · Jakub Skowronski🇮🇹 · Benjamin Brückner🇩🇪 · Sophia Dellmann🇺🇸 · Philipp Erbacher🇩🇪 · Tanja Heftrich🇩🇪 and 3 other authors

   We report a novel neutron-detection approach employing an EJ-309 liquid scintillator surrounded by six 3He proportional counters. Tests were performed at the FRANZ facility of the Goethe-University Frankfurt using the 7Li(p,n0)7Be reaction, producing neutrons across energies 50-720 keV. The scintillator's neutron energy quenching is determined, and its neutron/gamma-ray discrimination performance is evaluated. The lowest detectable neutron energy is 163 keV. EJ-309 - 3He counter neutron coincidences are compared with those from simulations. This array forms the prototype of a larger design, called scintillator-3He array for deep-underground experiments on the S-process, currently undergoing construction and testing for an upcoming deep-underground study of the 22Ne(alpha,n)25Mg reaction cross-section at the freshly-commissioned Bellotti Ion Beam facility of the INFN Laboratori Nazionali del Gran Sasso. This upcoming project is expected to achieve exceptionally low sensitivity for measuring the cross section at energies of interest for the astrophysical 'weak' and 'main' slow neutron-capture processes.

   ↳ physics.ins-detnucl-exJ.Phys.G(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.