Fri·Dec 12, 2025Friday·December 12, 2025

1. 01*

   Dileptons at Colliders as Probes of the Quark-Gluon Plasma

   R. Bailhache🇩🇪 · H. Appelshäuser🇩🇪

   Ultra-relativistic heavy-ion collisions are used to create a deconfined state of quarks and gluons, the quark-gluon plasma (QGP), similar to the matter in the early universe. Dileptons are a unique probe of the QGP. Being emitted during all stages of the collision without interacting strongly with the surrounding matter, they carry undistorted information about the medium evolution. The mass of the lepton-antilepton pair gives a unique mean to separate partonic from hadronic radiation. Thus, dileptons can be used to study the QGP equilibration time, its average temperature but also effects related to the restoration of chiral symmetry in the hot medium via vector meson decays. This information is not accessible with hadrons. The price to pay is a large background from ordinary hadron decays. We summarize the potential of dilepton measurements, the results obtained so far at colliders, and the ongoing efforts for future experiments with further increased sensitivity.

   nucl-exAnn.Rev.Nucl.Part.Sci.(2025)·3 citations
2. 02*

   Living on the edge: radius effects in the angular substructure of heavy-ion jets

   Carlota Andres🇫🇷 · Jack Holguin🇬🇧 · Benjamin Kimelman🇺🇸 · Raghav Kunnawalkam Elayavalli🇺🇸 · Jussi Viinikainen🇺🇸 · Zhong Yang🇺🇸

   Jet substructure observables serve as essential tools for probing the quark-gluon plasma produced in relativistic heavy-ion collisions. Their interpretation, however, is often complicated by edge effects, which arise when correlated particles fall outside the reconstructed jet radius, introducing distortions that obscure the underlying QCD dynamics. In this work, we present a comprehensive phenomenological study of edge effects in soft-insensitive angular observables, taking the two-point energy correlator (EEC) as a representative example. We argue that these distortions scale linearly with the average angular separation between the winner-take-all and $E$-scheme axes $⟨\varphi ⟩$, and validate this behavior across proton-proton (p-p) simulations with Pythia8 and Herwig7, as well as lead-lead (Pb-Pb) simulations using JEWEL and CoLBT. In p-p collisions, edge effects are strongly suppressed, scaling as $(R_L/R{)}^4$, whereas medium-modified jets can exhibit larger distortions, with contributions scaling as $(R_L/R{)}^2$ and $(R_L/R{)}^4$. Taking Pb-Pb/p-p ratios of the EEC substantially reduces, but does not completely eliminate, these distortions, highlighting the need of accounting for edge effects in the interpretation of heavy-ion jet substructure measurements. Since edge effects are largely governed by the $⟨\varphi ⟩$ distribution, studying this distribution provides a new handle for benchmarking and constraining the modeling of edge effects in heavy-ion event generators.

   ↳ hep-phhep-exnucl-exnucl-th5 citations
3. 03*

   Identifying Neutron Sources using Recoil and Time-of-Flight Spectroscopy

   David Breitenmoser · Ricardo Lopez · Shaun D. Clarke🇺🇸 · Sara A. Pozzi🇮🇹

   Neutron-source identification is central to nuclear physics and its applications, from planetary science to nuclear security, yet direct source discrimination from measured neutron spectra remains fundamentally elusive. Here, we introduce a Bayesian protocol that directly infers source ensembles from measured neutron spectra by combining full-spectrum template matching with probabilistic evidence evaluation. Applying this protocol to recoil and time-of-flight spectroscopy, we recover single- and two-source configurations with strong statistical significance ($>4\sigma$) at event counts as low as $\sim 10^3$. These results demonstrate that neutron spectral signatures can be leveraged for robust source identification, opening a new observational window for both fundamental research and operationally driven applications.

   ↳ physics.ins-detnucl-exphysics.app-phphysics.data-anPhys.Rev.Applied(2026)·1 citation
4. 04*

   Impact of the in-medium cross section on cluster spectra in ${}^{40,48}\mathrm{Ca}+{}^{58,64}\mathrm{Ni}$ collisions at $56$ and $140$ $\mathrm{MeV}/\mathbf{nucleon}$

   C.K. Tam🇺🇸 · Z. Chajecki🇺🇸 · R.S. Wang🇺🇸 · F.C.E. Teh🇺🇸 · N. Ikeno🇯🇵 · W.G. Lynch🇺🇸 · A. Ono🇯🇵 · M.B. Tsang🇺🇸 · A. Anthony🇺🇸 · S. Barlini🇮🇹 · J. Barney🇺🇸 · K.W. Brown🇺🇸 and 26 other authors

   Although significant efforts have been made to investigate the density dependence of the nuclear symmetry energy, the influence of the in-medium cross section on particle production in transport models is not well constrained. The in-medium cross section reflects the dynamic situation of the medium such as a nontrivial phase space distribution. In this study, we analyze the transverse momentum spectra of $p$, $d$, $t$, ${}^3\mathrm{He}$ and $\alpha$ particles emitted near mid-rapidity in central ${}^{40,48}\mathrm{Ca}$ + ${}^{58,64}\mathrm{Ni}$ reactions at $56$ and $140$ $\mathrm{MeV}/\mathrm{nucleon}$. The Antisymmetrized Molecular Dynamics ($\mathrm{AMD}$) model is chosen as the transport model for data comparison. Central events are selected based on charged-particle multiplicity in both the experimental data and AMD calculations after applying an experimental filter. Our results show that the in-medium nucleon-nucleon scattering cross-sections are more strongly reduced at $56$ $\mathrm{MeV}/\mathrm{nucleon}$ than at $140$ $\mathrm{MeV}/\mathrm{nucleon}$ incident energy.

   ↳ nucl-thnucl-ex0 citations
5. 05*

   Dynamical correlations across momentum scales in the Quark-Gluon Plasma

   Lipei Du🇺🇸 · P. M. Jacobs🇺🇸

   Experimental probes of the Quark-Gluon Plasma (QGP) generated in heavy-ion collisions span a broad range in momentum scale: low transverse momentum (low $p_T$) measurements probe collective dynamics, while high $p_T$ measurements probe the response to QGP excitation by jets (jet quenching). However, the dynamical interplay between QGP collective dynamics and jet quenching is currently poorly understood. We present a new framework for exploring dynamical correlations across momentum scales in heavy-ion collisions, based on the $p_T$-differential radial-flow observable $v_0(p_T)$. Measured $v_0(p_T)$ phenomenology is traced to the evolution in strength and coherence of distinct underlying fluctuation modes. We then propose new experimental observables to quantify this evolution. The eigenvalue ratio ${\lambda }_2/{\lambda }_1$ of the reference-aligned covariance matrix $V_0$ is shown to measure the effective fluctuation rank, while the $p_T$-dependence of the corresponding eigenvectors maps the evolution from a single coherent soft mode to multi-mode dynamics including coalescence and jet quenching. These observables map the soft-mid-hard correlation structure and provide a unified description of the collective-to-partonic transition in the QGP.

   ↳ nucl-thhep-phnucl-exPLB(2026)·3 citations
6. 06*

   Three-body resonances of $\alpha \alpha M$ clusters ($M=\varphi$, $J/\psi$, ${\eta }_c$) in ${}_M^8\mathrm{Be}$ nuclei

   Hao Zhou🇨🇳 · Xiang Liu🇨🇳

   Motivated by the recently obtained HAL QCD potentials for the $N$-$\varphi$, $N$-$J/\psi$, and $N$-${\eta }_c$ interactions, we investigate the structure of the exotic nuclei ${}_{\varphi }^8\text{Be}$, ${}_{J/\psi }^8\text{Be}$, and ${}_{{\eta }_c}^8\text{Be}$ as $\alpha +\alpha +M$ three-body systems ($M$ denotes the meson). The bound and resonant states are calculated consistently using the Gaussian expansion method, with resonances identified via the complex scaling method. For the $\alpha \varphi$ and $\alpha$-charmonium interactions, a folding potential is constructed based on the HAL QCD potentials and fitted to a Woods-Saxon form. We find that the $\varphi$ meson exhibits a strong ``glue-like" effect, binding the $0_1^{+}$, $2_1^{+}$, and $4_1^{+}$ resonant states of ${}^8$Be into stable states and significantly reducing the $\alpha$-$\alpha$ distance. In contrast, the interactions of $J/\psi$ and ${\eta }_c$ with the nucleus are weaker, forming only shallow bound states with the $0_1^{+}$ state of ${}^8$Be and even increasing the $\alpha$-$\alpha$ separation. Notably, our analysis predicts weakly bound $\alpha$-$J/\psi$ states in the ${}^4{S}_{3/2}$ and ${}^2{S}_{1/2}$ channels, a result not reported in prior studies, which suggests that ${}_{J/\psi }^8\text{Be}$ may not be a Borromean nucleus. The sensitivity of the ${}_M^8\mathrm{Be}(4_1^{+})$ state-transitioning from bound to resonant depending on the $\alpha$-particle radius-highlights the subtle dynamics at play. These results provide a systematic theoretical comparison of how different vector mesons modify nuclear clustering, offering critical predictions for future experimental searches of such exotic hadron-nucleus systems.

   ↳ hep-phhep-exnucl-exnucl-thPRD(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.