Nuclear Theory·nucl-th

Wednesday·May 21, 2025

12 papers—4 primary·8 cross-listed

01
Unified nonparametric equation-of-state inference from the neutron-star crust to perturbative-QCD densities
Eliot Finch🇺🇸 · Isaac Legred🇺🇸 · Katerina Chatziioannou🇺🇸 · Reed Essick🇨🇦 · Sophia Han🇨🇳 · Philippe Landry🇨🇦
Perturbative quantum chromodynamics (pQCD), while valid only at densities exceeding those found in the cores of neutron stars, could provide constraints on the dense-matter equation of state (EOS). In this work, we examine the impact of pQCD information on the inference of the EOS using a nonparametric framework based on Gaussian processes (GPs). We examine the application of pQCD constraints through a "pQCD likelihood," and verify the findings of previous works; namely, a softening of the EOS at the central densities of the most massive neutron stars and a reduction in the maximum neutron-star mass. Although the pQCD likelihood can be easily integrated into existing EOS inference frameworks, this approach requires an arbitrary selection of the density at which the constraints are applied. The EOS behavior is also treated differently on either side of the chosen density. To mitigate these issues, we extend the EOS model to higher densities, thereby constructing a "unified" description of the EOS from the neutron-star crust to densities relevant for pQCD. In this approach the pQCD constraints effectively become part of the prior. Since the EOS is unconstrained by any calculation or data between the densities applicable to neutron stars and pQCD, we argue for maximum modeling flexibility in that regime. We compare the unified EOS with the traditional pQCD likelihood, and although we confirm the EOS softening, we do not see a reduction in the maximum neutron-star mass or any impact on macroscopic observables. Though residual model dependence cannot be ruled out, we find that pQCD suggests the speed of sound in the densest neutron-star cores has already started decreasing toward the asymptotic limit; we find that the speed of sound squared at the center of the most massive neutron star has an upper bound of $\sim 0.5$ at the $90%$ level.
nucl-thastro-ph.HEgr-qcPRD(2025)·15 citations
02
Searching for entanglement in final polarization states of the neutron-proton scattering
H. Witała🇵🇱 · J. Golak🇵🇱 · R. Skibiński🇵🇱
We investigate polarization states of the outgoing neutron-proton ( $n p$ ) pair in elastic polarized neutron and proton scattering, aiming to find unambiguous evidence for entanglement of their spin states. To obtain complete information about these states, we calculate, using the high precision nucleon-nucleon potential AV18, the final polarizations of the neutron and proton as well as their spin correlation coefficients, which unequivocally define the corresponding spin density matrix. We compute all terms contributing to polarizations and spin correlations, e.g. not only induced polarizations and correlations resulting from unpolarized $n p$ scattering, but also contributions from single polarization and correlation transfers from individual polarized incoming nucleons, and, for the first time, allotment to both quantities stemming from a doubly spin polarized initial state. We find that for the most part the final spin states are statistical mixture of states.The only pure states occur for highly polarized incoming neutrons and protons with maximal polarizations. By quantifying the degree of entanglement through entanglement power and concurrence, we observed that the entanglement of impure final states increases with energy. Among the pure spin states resulting from incoming states with maximal neutron and proton polarizations, we found, at $E_{l ab} = 100$ ~MeV, cases of strongly entangled Bell-type states with only a small admixture of entanglement-spoiling contributions.
nucl-thPRC(2025)·9 citations
03
Classifying metal-poor stars with machine learning using nucleosynthesis calculations
Nicole Vassh · Yilin Wang · Richard M. Woloshyn · Michelle P. Kuchera · Maude Lariviere · Kayle Majic · Benoit Cote
We apply the capabilities of machine learning (ML) to discern patterns in order to classify metal-poor stars. To do so, we train an ML model on a bank of nucleosynthesis calculations derived from hydrodynamic simulations for events such as neutron star mergers where the rapid ( $r$ ) neutron capture process can take place. Likewise we consider a bank of calculations from simulations of the slow ( $s$ ) neutron capture process and also consider a few calculations for the intermediate ( $i$ ) neutron capture process. We demonstrate that the ML does well overall in recognizing the $s$ process from the $r$ process, and after training on theoretical calculations ML stellar assignments match conventional labels 87% of the time. We highlight that this method then points to stars that could benefit from additional observational measurements. We also demonstrate that the ML assigns some of the presently considered $i$ -process stars to instead be of $r$ or $s$ in origin, but likewise, finds stars currently labeled as $s$ to be potentially more aligned with $i$ enrichment. This first application of ML to classify metal-poor star enrichment using theoretical nucleosynthesis calculations thus reveals the promise, and some challenges, associated with this new data-driven path forward.
nucl-thastro-ph.GAastro-ph.SRApJ(2025)·0 citations
04
Left-right splitting of elliptic flow in heavy ion collisions: TRENTo-3D initialization and CLVisc hydrodynamic simulations
Ze-Fang Jiang🇨🇳 · Xiang Fan🇨🇳 · Duan She🇨🇳 · Shasha Ye🇨🇳 · Ben-Wei Zhang🇨🇳
Using the TRENTo-3D initial condition model coupled with (3+1)-dimensional CLVisc hydrodynamic simulations, we systematically investigate the left-right splitting of elliptic flow ( $Δ v_{2}$ ) for soft particles in relativistic heavy-ion collisions. Our study reveals that the final distribution characteristics of $Δ v_{2}$ are primarily depend on the odd flow harmonics and $v_{2}$ itself. We find that the parton transverse momentum scale $k_{T}$ not only determines the geometric tilt of the QGP fireball but also significantly affects the rapidity dependence of both $v_{1}$ and $Δ v_{2}$ , providing new insights into the splitting mechanism of $Δ v_{2}$ . Furthermore, our results demonstrate that $Δ v_{2} (p_{T})$ exhibits significant sensitivity to influences such as the sub-nucleonic degrees of freedom (or `hotspots'), transverse momentum scale, and fragmentation region profile. By analyzing the $Δ v_{2}$ and $Δ v_{2} / v_{2}$ ratio, our findings provide new constraints on the uncertainties of the QGP initial state and provide additional constraints for refining model parameters.
nucl-thhep-phPRC(2025)·2 citations
05
A modern Fortran library for SU(3) coupling and recoupling coefficients
Jakub Herko🇺🇸 · Mark A. Caprio🇺🇸 · Anna E. McCoy🇺🇸 · Patrick J. Fasano🇺🇸
The group $SU (3)$ has applications in several branches of physics. Many of these applications depend on availability of $SU (3)$ coupling and recoupling coefficients. We have developed a modern Fortran library for calculation of the coupling coefficients, for both the $SU (3) \supset U (1) \times SU (2)$ and $SU (3) \supset SO (3)$ group chains, and the recoupling coefficients. The library implements the algorithms of Draayer, Akiyama, and Millener, which are laid out in the paper. Performance of the library has been tested and compared to the Akiyama-Draayer (AD) library implementing the same algorithms as well as to a more recent implementation. Our library works for a larger range of $SU (3)$ quantum numbers and provides more accurate coupling coefficients with large quantum numbers than the AD library.
↳ physics.comp-phnucl-thEPJA(2026)·1 citation
06
An Improvement of AmpRed: Analytic Continuation of Complex Integrals
Wen Chen🇨🇳
The AmpRed package has been updated with an improved method for analytic continuation of complex integrals. Compared to the previous version, the new implementation significantly enhances computational efficiency for evaluating complex integrals.
↳ hep-phhep-thnucl-th6 citations
07
Proton Structure Functions from Holographic Einstein-Dilaton Models
Ayrton da Cruz Pereira do Nascimento · Henrique Boschi-Filho · Jorge Noronha
We study the proton structure functions $F_{1}$ and $F_{2}$ in the context of holography. We develop a general framework that extends previous holographic calculations of $F_{1}$ and $F_{2}$ to the case where the bulk geometry stems from bottom-up Einstein-Dilaton models, which are commonly used in the literature to describe some properties of QCD in the strong coupling regime. We focus on a choice of the dilaton potential that leads to a holographic model able to reproduce known lattice QCD results for the glueball masses at zero temperature and pure Yang-Mills thermodynamics above deconfinement. Once the parameters of the background holographic model are fixed, we introduce probe fermionic and gauge fields in the bulk {\it a la} Polchinski and Strassler to determine the corresponding structure functions. This particular realization of the model can successfully describe the proton mass and provide results for $F_{2}$ at large $x$ in very good agreement with experimental data.
↳ hep-thhep-phnucl-th3 citations
08
Investigating quarkonium collectivity in heavy-ion collisions
Victor Valencia Torres🇫🇷
The quark-gluon plasma (QGP) produced in ultrarelativistic heavy-ion collisions has exhibited properties of a mostly perfect fluid. These properties can be observed through the hydrodynamic expansion of the QGP. Experimentally, this was established by measuring azimuthal anisotropies in the final state, known as elliptic flow ( $v_{2}$ ) or higher order harmonics such as triangular flow ( $v_{3}$ ). These Fourier harmonic coefficients have been extensively measured in past experiments using inclusive charged particles or identified particles in the soft sector. Interestingly, measuring such coefficients using hard probes, such as quarkonia, brings additional information about heavy-quarks production and thermalization in the QGP. In this study, we investigate quarkonia collectivity using Run 3 data collected in 2023, presenting new flow measurements. We employ different experimental methods to extract flow coefficients, including the scalar product, event plane, and cumulant methods. These results will impose new constraints on theoretical models, enhancing our understanding of quarkonia behavior in heavy-ion collisions.
↳ hep-exhep-phnucl-th2 citations
09
Photoproduction of heavy vector mesons in peripheral $P b P b$ collisions at the Large Hadron Collider
Pedro E. A. da Costa🇧🇷 · André V. Giannini🇧🇷 · Victor P. Goncalves🇧🇷 · Bruno D. Moreira🇧🇷
A comprehensive analysis of the photoproduction of $J /Ψ$ and $Υ$ mesons in peripheral $P b P b$ collisions at the center - of - mass energies of the Large Hadron Collider (LHC) is performed, considering distinct assumptions for the modeling of the nuclear photon flux, photon - nucleus cross - section, overlap function and dipole - proton scattering amplitude. The comparison of these predictions with the ALICE data is also performed. Our results indicate that a detailed analysis of the production of both mesons will be very useful to improve the description of photon - induced processes in peripheral collisions.
↳ nucl-exhep-exhep-phnucl-thPRD(2025)·2 citations
10
Magnetic properties of the hadron resonance gas with physical magnetic moments
Rupam Samanta🇵🇱 · Wojciech Broniowski🇵🇱
We study magnetic properties of the Hadron Resonance Gas in the presence of a strong ( $0 \leq B \leq 0.15 GeV^{2}$ ) uniform magnetic field, using physical values of the magnetic moments of hadrons, i.e., including their anomalous parts. The values of these moments are taken from experiment, or when unavailable, from theoretical estimates. We evaluate the conserved charge susceptibilities, finding the expected sizable effects of the anomalous magnetic moments, in particular of the octet baryons, such as the proton and neutron, where they are exceptionally large. We also study in detail the large effects of the magnetic moments of the $Δ (1232)$ states, for which various theoretical estimates and experimental values differ significantly. We compare our model results with the lattice QCD data and find reasonable agreement within the model uncertainty.
↳ hep-phhep-latnucl-thPRC(2025)·5 citations
11
Statistical analysis of pQCD energy loss across system size, flavor, $s_{N N}$ , and $p_{T}$
Coleridge Faraday🇿🇦 · W. A. Horowitz🇿🇦
We present suppression predictions from our pQCD-based energy loss model, which receives small system size corrections, for high- $p_{T}$ $π$ , $D$ and $B$ meson $R_{A B}$ as a function of centrality, flavor, $s_{N N}$ , and $p_{T}$ from large to small collision systems at RHIC and LHC. A statistical analysis is used to constrain the effective strong coupling in our model to available high- $p_{T}$ suppression data from central heavy-ion collisions at RHIC and LHC, yielding good agreement with all available data. We estimate two important theoretical uncertainties in our model, stemming from: the transition between vacuum and hard thermal loop propagators in the collisional energy loss, and from the angular cutoff on the radiated gluon momentum. We find, consistently, that the extracted $α_{s}$ remains relatively unchanged across heavy- and light-flavor final states and across central, semi-central, and peripheral collisions. We make predictions from our large-system-constrained model for small systems and find good agreement with photon-normalized $R_{d Au}^{π^{0}} ≃ 0.75$ in $0 - 5%$ centrality $d$ + Au collisions by PHENIX. However, we find strong disagreement with the measured $R_{p Pb}^{h^{\pm}} ≳ 1$ in $0 - 5%$ centrality $p$ + Pb collisions by ALICE and ATLAS; we argue that this disagreement is due, in large part, to centrality bias. We make predictions for the ratio of suppression in $^{3}$ He + Au and $p$ + Au collisions, which may in the future be used to disentangle final- from initial-state suppression in small systems. We then compare our results to various subsets of data, which allows us to estimate the preferred: low- $p_{T}$ scale at which non-perturbative processes become important, scales at which the strong coupling runs, and scale at which vacuum propagators transition to thermally modified propagators in collisional energy loss.
↳ hep-phnucl-thJHEP(2025)·15 citations
12
Large-Momentum Effective Theory's Asymptotic Extrapolation vs the Inverse Problem
Jiunn-Wei Chen🇹🇼 · Xiang Gao🇺🇸 · Jinchen He🇺🇸 · Jun Hua🇨🇳 · Xiangdong Ji🇺🇸 · Andreas Schäfer🇹🇼 · Yushan Su🇺🇸 · Wei Wang🇨🇳 · Yi-Bo Yang🇨🇳 · Jian-Hui Zhang🇨🇳 · Qi-An Zhang🇨🇳 · Rui Zhang🇺🇸 · Yong Zhao🇺🇸
Large-Momentum Effective Theory (LaMET) is a physics-guided systematic expansion to calculate light-cone parton distributions, including collinear (PDFs) and transverse-momentum-dependent ones, at any fixed momentum fraction $x$ within a range of $[x_{min}, x_{max}]$ . It theoretically solves the ill-posed inverse problem that afflicts other theoretical approaches to collinear PDFs, such as short-distance factorizations. Recently, arXiv:2504.17706 [1] raised practical concerns about whether current or even future lattice data will have sufficient precision in the sub-asymptotic correlation region to support an error-controlled extrapolation -- and if not, whether it becomes an inverse problem where the relevant uncertainties cannot be properly quantified. While we agree that not all current lattice data have the desired precision to qualify for an asymptotic extrapolation, some calculations do, and more are expected in the future. We comment on the analysis and results in Ref. [1] and argue that a physics-based systematic extrapolation still provides the most reliable error estimates, even when the data quality is not ideal. In contrast, re-framing the long-distance asymptotic extrapolation as a data-driven-only inverse problem with ad hoc mathematical conditioning could lead to unnecessarily conservative errors.
↳ hep-lathep-phnucl-thPRD(2026)·20 citations

Affiliations

first authorsco-authorsvia INSPIRE