Nuclear Theory·nucl-th

Friday·July 31, 2026

12 papers—4 primary·8 cross-listed

05
Photon-calibrated event-activity bias and subcollision geometry in d+Au collisions at $s_{N N}$ = 200 GeV with PYTHIA 8 Angantyr
Muhammad Ajaz🇸🇦 · Haifa I. Alrebdi🇸🇦 · Muhammad Waqas🇨🇳
Event-activity selections in small nuclear collision systems couple collision geometry to the soft response accompanying a hard scattering. We examine this coupling in d+Au collisions at $s_{N N}$ = 200 GeV with PYTHIA 8.316 Angantyr, using direct photons, terminal pre-decay neutral pions, and anti-kT jets. A hard-bias factor compares the probability for a hard event to enter an activity class with an $N_{co l l}^{N D}$ -weighted minimum-bias reference. The model predicts a depleted most-active class and an enhanced peripheral class for both photons and pions. Photon-tagged events also sample a smaller mean impact parameter and more nondiffractive subcollisions than pion-tagged or inclusive HardQCD events. Comparing fully correlated Angantyr events with an Ncoll-reweighted minimum-bias reference and a factorized diagnostic separates the explicit geometric contribution from residual hard-soft correlations. STAR-like and PHENIX-like particle-level activity proxies preserve the class ordering but give different class probabilities. The calculation is generator-level and does not identify a unique microscopic origin for the residual correlations.
↳ hep-phnucl-exnucl-th0 citations
06
Unbiased Data-Driven Determination of the Nuclear Dipole Amplitude in the Color Glass Condensate
Si-Wei Dai🇨🇳 · Haowu Duan🇨🇳 · Long-Gang Pang🇨🇳 · Guang-You Qin🇨🇳 · Shu-Yi Wei🇨🇳 · Han-Zhong Zhang🇨🇳 · Wenbin Zhao🇨🇳
Gluon saturation limits the growth of parton densities at small Bjorken- $x$ and is expected to be most pronounced in heavy nuclei. Yet quantitative extractions of the nuclear gluon dipole amplitude have long relied on parametrized initial conditions, introducing uncontrolled model dependence that obscures genuine nuclear effects. We introduce a physics-informed neural-network framework that embeds the collinearly improved Balitsky-Kovchegov evolution equation directly into the training objective, allowing the impact-parameter-averaged dipole amplitude to be determined from data without assuming a functional form for its initial condition. Applying this framework to forward-hadron nuclear-modification-factor and coherent $J / ψ$ photoproduction data, we extract the $^{208}$ Pb dipole amplitude at $x_{0} = 0.01$ with QCD evolution and momentum-space positivity enforced throughout training. The evolved amplitude reproduces the measured cross sections across the available kinematic range and yields a saturation-scale ratio $Q_{s 0, Pb}^{2} / Q_{s 0, p}^{2} = 3.1 7_{- 0.10}^{+ 0.17}$ , consistent with simple geometric scaling. The extracted Pb initial condition is well described by a McLerran-Venugopalan-type form, in contrast to the proton, reflecting the higher color-charge density of a large nucleus. Using the same amplitude, we predict the rapidity dependence of the transverse-momentum ratio in $pp$ , $p$ Pb, and Pb $p$ collisions, finding agreement with recent LHCb measurements at low multiplicity without any system-dependent parameters. This work provides the first unbiased, data-driven determination of nuclear structure in the saturation regime and establishes a general strategy for embedding nonlinear evolution equations into machine-learning extractions of dynamically constrained observables.
↳ hep-phnucl-exnucl-th2 citations
07
A regulated zero-temperature construction of the Fundamental Modular Region in pure Yang--Mills theory and QCD
Rodrigo Carmo Terin🇪🇸
We formulate the Fundamental Modular Region (FMR) as the zero-temperature limit of regulated copy-weighted Landau gauges. At finite $β$ , the measure localizes on absolute minima, and the leading correction is dominated by the inverse Faddeev--Popov (FP) operator. A small $S U (2)$ benchmark provides a computational realization through population annealing and collective basin hopping. Our construction defines absolute Landau gauge without parametrizing the FMR boundary and extends naturally to full quantum chromodynamics (QCD). It also admits a Hamiltonian interpretation in terms of the gauge-fixed vacuum wave functional on the FMR.
↳ hep-thhep-lathep-phnucl-th0 citations
08
Impact of Kaon Condensation on the Thermal Evolution of the CCO in HESS J1731--347 Supernova Remnant
D.G. Nanopoulos🇬🇷 · P.S. Koliogiannis🇭🇷 · V. Petousis🇨🇿 · M. Veselsky🇨🇿 · Ch.C. Moustakidis🇬🇷
Recent analyses of the central compact object in the HESS J1731--347 supernova remnant suggest an unusual combination of a low mass and small radius, while its thermal emission indicates a relatively high surface temperature at its estimated age. Reconciling these structural and thermal properties within a unified theoretical framework may provide important constraints on the equation of state and composition of dense matter. In this work, we investigate the thermal consequences of negatively charged kaon condensation, an exotic phase that softens the equation of state and facilitate the reproduction of the inferred bulk properties of HESS J1731--347. We find that the onset of kaon condensation strongly accelerates the thermal evolution, leading to surface temperature substantially below the observationally inferred range. Within the adopted cooling framework, kaon condensation therefore cannot simultaneously account for the structural and thermal properties of HESS J1731--347.
↳ astro-ph.HEastro-ph.GAastro-ph.SRnucl-th0 citations
09
Probing (Hyper)Nuclei Wave Functions and Production Mechanisms in $s_{NN} = 200$ GeV Isobar Collisions at RHIC
STAR Collaboration
The study of nuclei and hypernuclei production is a powerful tool to investigate the formation mechanism of loosely bound states in high-energy heavy-ion collisions. A key prediction from coalescence models is a strong suppression of the hypertriton ( $_{Λ}^{3} H$ ) compared to $^{3} He$ production in small collision systems due to the larger radius of $_{Λ}^{3} H$ . In this letter, the STAR collaboration reports measurements on (hyper)nuclei ( $_{Λ}^{3} H,_{Λ ˉ}^{3} H ˉ,^{3} He,^{3} He, t$ ) production at mid-rapidity in Ru+Ru and Zr+Zr collisions at $s_{NN} = 200$ GeV as a function of collision centrality. We find that the ratios $N_{t} N_{p} / N_{d}^{2}$ and $S_{3} = (N_{_{Λ}^{3} H} / N_{_{3} He}) / (N_{Λ} / N_{p})$ deviate significantly from thermal model expectations. Coalescence calculations incorporating realistic non-Gaussian wave functions for the $d$ and $_{Λ}^{3} H$ provide an improved description of the data, while Gaussian descriptions of the $_{Λ}^{3} H$ wave function fail to simultaneously reproduce the measured $S_{3}$ and the binding energy of $_{Λ}^{3} H$ . These results suggest that the $_{Λ}^{3} H$ wave function contains larger short-distance $d$ -- $Λ$ probability than implied by a Gaussian ansatz, demonstrating the potential of heavy-ion production measurements as a probe of hypernuclear wave functions and the underlying hyperon--nucleon interaction.
↳ nucl-exhep-exhep-phnucl-th1 citation
10
Estimating amplitude of matter density fluctuations in solar and supernova models using neutrino flavor evolution
Caroline Laber-Smith🇺🇸 · Hansen Torres🇺🇸 · Lily Newkirk🇺🇸 · Dhriti Rathod🇺🇸 · A. Baha Balantekin🇺🇸 · Amol V. Patwardhan🇺🇸
Neutrinos can undergo substantial flavor evolution between their production in astrophysical sources-such as the Sun and core-collapse supernovae-and their subsequent detection in terrestrial detectors. This flavor evolution is strongly influenced by the environment that the neutrinos interact with, making them useful astrophysical messengers capable of potentially carrying information about the properties of the source wherein they are produced. In this work, we apply the framework of statistical data assimilation (SDA) in order to ascertain the extent to which a neutrino signal at detection may contain information about matter density fluctuations along their path from the source. Using simplified models of neutrino flavor evolution and propagation in the sun and in a core-collapse supernova (CCSN), we find that the SDA method is able to extract information about the amplitude of density fluctuations in both the solar and CCSN scenarios, with the method showing relatively greater reliability in the solar neutrino case. Nonetheless, even in the CCSN neutrino model, the method proved effective at high fluctuation amplitudes
↳ astro-ph.HEhep-phnucl-th0 citations
11
Binary neutron stars in the next-generation era: Multi-messenger detection prospects and constraints on the equation of state, mass distribution, and cosmology
Hauke Koehn · Thibeau Wouters · Gilad Sadeh · Peter T.H. Pang · Mattia Bulla · Chris Van Den Broeck · Michael W. Coughlin · Tim Dietrich
Next-generation gravitational-wave (GW) observatories will provide crucial insights into the nature of neutron star (NS) matter and the cosmological expansion history. We estimate the number of multi-messenger detections from binary neutron stars (BNS) with the Einstein Telescope (ET) and Cosmic Explorer (CE), and project the resulting constraints on the equation of state (EOS), BNS mass distribution, and cosmology via joint hierarchical Bayesian inference. Assuming a local merger rate of 106.6 Gpc $^{- 3}$ yr $^{- 1}$ and considering two different mass functions, a narrow one centred around 1.4 $M_{⊙}$ and a wide one ranging between 1.1--2 $M_{⊙}$ , we find that for ET, our mock follow-up algorithm results in at least $\sim 40$ and up to $\sim 100$ successfully identified electromagnetic counterparts per year, depending on the detector layout and mass distribution. In a joint network with CE, the number of multi-messenger detections can range from $\sim 200$ to $\sim 500$ . Additionally, several more afterglows from gamma-ray bursts or KNe could be found with dedicated late-time observations. Based on the identified multi-messenger events, we perform an injection campaign to hierarchically constrain the EOS, mass distribution, and cosmology in a fully Bayesian framework. Focussing on ET alone, we show how in an ideal scenario, GW signals, KNe, and host galaxy redshifts can constrain the canonical NS radius $R_{1.4}$ within $\sim 0.2$ km and the Hubble constant $H_{0}$ within $\sim 1$ km s $^{- 1}$ Mpc $^{- 1}$ , while recovering the essential features of the mass distribution. By comparing inference results that rely solely on GW data and those that incorporate light curve information, we find that while KN light-curve posteriors have a negligible impact on the EOS constraints, they can benefit the inference of cosmological parameters.
↳ astro-ph.HEastro-ph.COnucl-th0 citations
12
Exact chiral symmetry with quantum signal processing
Henry Lamm🇺🇸 · Alessandro Roggero🇮🇹 · Hersh Singh🇺🇸 · Luca Spagnoli🇮🇹
We give a quantum signal processing (QSP) algorithm for the overlap fermion Hamiltonian which preserves the Ginsparg-Wilson relation up to a controllable error $ϵ_{e}$ . Quantum simulations of Dirac fermions with exact chiral symmetry are thus nearly free: applying the overlap Hamiltonian costs only a factor logarithmic in $ϵ_{e}$ more than the Wilson-Dirac Hamiltonian. Comparing to domain-wall fermions, a mild overhead is found in circuit complexity while reducing qubit costs. We show how QSP effectively constructs an extra dimension when simulating the overlap operator, illustrating that the scaling of quantum algorithms reflects the deeper physics of overlap fermions arising at the boundary of domain-wall fermions.
↳ hep-latnucl-thquant-ph1 citation

Affiliations

first authorsco-authorsvia INSPIRE