Nuclear Theory·nucl-th

Friday·June 26, 2026

9 papers—6 primary·3 cross-listed

01
Studying the QCD Matter produced in Heavy-Ion Collisions using the MUSES Calculation Engine
Johannes Jahan · Kevin P. Pala · Yumu Yang · Isabella Danhoni · Prachi Garella · Jonathan Gonzales · Joaquin Grefa · Mauricio Hippert · Surkhab Kaur Virk · Micheal Kahangirwe · Musa R. Khan · Feyisola Nana and 33 other authors
The equation of state of hot and dense matter is essential for describing heavy-ion collisions at all collision energies. Here, we explore the capabilities of the latest version of the MUSES Calculation Engine, $Calliope$ , focusing on software modules and workflows that compute the equation of state and observable properties of the matter produced in heavy-ion collisions. These include several equations of state, ranging from first-principles lattice QCD to phenomenological approaches, with or without a critical point, and with phase-space dimensionality ranging from two dimensions defined by temperature $T$ and baryon chemical potential $μ_{B}$ , to four dimensions after the addition of strangeness and electric-charge chemical potentials $μ_{S}$ and $μ_{Q}$ . We also discuss modules that provide additional thermodynamic quantities and observables relevant for heavy-ion modeling, including elements of the pressure Hessian matrix and transport coefficients. Workflow examples are constructed that merge two equations of state thermodynamically consistently to extend phase-diagram coverage, and feed the results into an equation of state inverter to produce inputs suitable for hydrodynamic simulations. Finally, we apply this framework to perform a relativistic viscous hydrodynamic simulation with equations of state with an extended $T$ and $μ_{B}$ coverage and a movable critical point, including effects from transport coefficients that phenomenologically encode critical scaling, at collision energies $s_{N N} = 7.7, 19.6$ , and $39$ GeV.
nucl-thhep-ph6 citations
02
Thermal Effects on the Moment of Inertia and Gravitational Redshift of PSR J1012+5307: Implications for Hyperonic Matter under SU(3) and SU(6) Symmetries
Y.Xu🇨🇳 · X.L.Huang🇨🇳 · Y.B.Wang🇨🇳 · Q.Yuan🇨🇳 · W.B.Ding🇨🇳 · N.An🇨🇳 · Y.F.Shen🇨🇳 · Z.Yu🇨🇳
The temperature dependence of neutron star structure significantly alters the equation of state, thereby affecting observable properties such as the moment of inertia and gravitational redshift. Utilizing the relativistic mean-field theory with hyperonic degrees of freedom under SU(3) flavor and SU(6) spin-flavor symmetries, we investigate the thermal effects on the structural properties of protoneutron stars and cold neutron stars. Focusing on PSR J1012+5307, we analyze the drastic structural transformations occurring during the transition from a PNS to a CNS. For a 1.94 Msun hyperonic star under SU(3) flavor symmetry, decreasing the temperature from T =30 MeV to 0 MeV induces a radius contraction of approximately 50 percent, accompanied by a drop in the moment of inertia by nearly 26% and a significant increase in gravitational redshift by approximately 154 percent. Furthermore, we examine the variations in the moment of inertia and gravitational redshift arising from mass uncertainties of PSR J1012+5307.Taking SU(3) flavor symmetry at T =20 MeV as an example, increasing the mass across the range 1.72 Msun to 1.94Msun results in a radius contraction of 2.749 km, an 8 percent increase in the moment of inertia, and a significant 40 percent increase in the gravitational redshift.We find that in the cold regime and at a fixed mass, the radius, moment of inertia,and gravitational redshift of hyperonic matter under SU(3) flavor symmetry differ only marginally from those of purely nucleonic matter, rendering it difficult to observationally confirm the presence of hyperons in the core of PSR J1012+5307. Moreover, future observations capable of precisely constraining pulsar masses,ideally through long-termonitoring from birth,hold the potential to determine more conclusively whether hyperons or other exotic matter reside in individual pulsars.
nucl-th0 citations
03
The $^{229}$ Th Isomer: Nuclear Structure, Clocks, and Tests of Fundamental Physics
Xiao Lu🇨🇳 · Rui Zhao🇨🇳 · Shan-Gui Zhou🇨🇳
The $^{229}$ Th nucleus possesses an isomeric state at an excitation energy of $\sim 8$ eV, the lowest known nuclear transition energy, placing its frequency in the vacuum-ultraviolet range and making it directly accessible to laser spectroscopy. In this review, we discuss the $^{229}$ Th isomer from three connected perspectives: experimental spectroscopy and clock development, nuclear structure theory, and applications to precision tests of fundamental physics. We first trace the experimental progress from indirect $γ$ -ray energy inference to resonant laser excitation, absolute frequency comparison with an atomic clock, and feedback-loop operation of a solid-state nuclear clock, and discuss trapped-ion, highly charged ion, and solid-state platforms together with mechanisms for nuclear-state manipulation and readout. We then review, from the nuclear-structure perspective, how the near-degeneracy of the $5/ 2^{+} [633]$ and $3/ 2^{+} [631]$ neutron Nilsson configurations, together with Coriolis mixing and octupole correlations, underlies the anomalously low transition energy and its electromagnetic properties. Comparisons among different phenomenological and microscopic models show that octupole correlations are a common structural ingredient, while magnetic moments and transition strengths remain sensitive tests of the calculated wave functions. Finally, we discuss how the near-cancellation of MeV-scale nuclear contributions into an eV-scale transition can enhance sensitivity to variations of fundamental constants, signatures of ultralight dark matter, CP-violating interactions, Lorentz-invariance violation, and possible nuclear quantum technologies.
nucl-thChin.Phys.B(2026)·1 citation
04
Applicability of kinetic theory in strongly coupled thermal quantum systems
Shile Chen · Shuzhe Shi · Pengfei Zhuang
In this work, we construct one-dimensional interacting lattice spinor theories with discretization in momentum space. We focus on strongly interacting Schwinger and Nambu--Jona-Lasinio models and perform ab-initio calculation of their single-particle and two-particle momentum distribution functions at finite temperature. We observe, at low temperature, high-momentum tail in single-particle and two particle distribution which reveals relative momentum in fermion-antifermion boundstates, as well as quasi-free spinor gases behavior at high temperature. The non-vanishing connected four-momentum function reveals the quantum coherence in momentum space under thermal equilibrium of the system and indicate the single particle correlation would remember more microscopic details within a thermal system. Overall, for a high-enough temperature at which the thermal kinetic energy comparable with the interaction, we observe that the two-particle correlation is subdominant compared to the single particle distributions, which indicates the applicability of kinetic theory.
nucl-thhep-ph0 citations
05
Challenging chiral EFT with tritium beta decay
D.F. Ramirez Jimenez🇵🇱 · S. Heihoff🇩🇪 · J. Golak🇵🇱 · E. Epelbaum🇩🇪 · H. Krebs🇩🇪 · P. Reinert🇩🇪 · R. Skibinski🇵🇱 · K. Topolnicki🇵🇱 · H. Witala
We present a detailed investigation of tritium beta decay up to third order (N2LO) in chiral effective field theory (EFT) using the LENPIC interactions. Unlike existing studies, we use nucleon-deuteron scattering observables to fix the low-energy constant D that governs the strength of the short-range contributions to the exchange axial current operator and three-nucleon forces. Surprisingly, the resulting parameter-free predictions for the tritium Gamow-Teller reduced matrix element are found to considerably overestimate its empirical value. This result remains robust against reasonable variations of the pion-nucleon coupling constants and regularization scheme. A closer look at the size of the parameter-free long-range two-body contributions to the Gamow-Teller matrix element reveals the fine-tuned nature this observable in chiral EFT, which may partially explain the observed deviation. Our results indicate a considerable N2LO truncation uncertainty for tritium beta decay and point towards large higher-order two-body corrections. More definite conclusions await a complete fourth-order analysis of nucleon-deuteron scattering observables and tritium half-life.
nucl-th2 citations
06
Rapidity-even directed flow splitting of protons and antiprotons as a probe of baryon stopping in relativistic heavy-ion collisions
Tribhuban Parida🇮🇳 · Sandeep Chatterjee🇮🇳
We compare the rapidity-even directed flow $v_{1}^{even}$ in Au+Au collisions at Beam Energy Scan (BES) energies for baryons and anti-baryons within a (3+1)-dimensional viscous relativistic hydrodynamics coupled to hadronic transport framework. The double-junction baryon stopping picture motivates a rapidity-even component in the baryon deposition in the initial state. We demonstrate that the split in the $v_{1}^{even}$ of protons and anti-protons is sensitive to the rapidity extension of the baryon deposition that we associate with the double junction baryon stopping. Particularly, we find that the mid-rapidity curvature $\frac{d ^{2} Δ v _{1}^{even} ( p - p ˉ )}{d y ^{2}} ∣_{y = 0}$ is a robust discriminator of the initial state baryon rapidity profiles. A simultaneous measurement of $Δ v_{1}^{even}$ and its curvature at mid-rapidity could constrain both the baryon diffusion strength and the baryon stopping profile, providing access to the physics of baryon stopping in relativistic heavy ion collisions.
nucl-thhep-phnucl-ex1 citation
07
The odd fermion at the edge: odd-even staggering in the trapped, unitary Fermi gas
Silas R. Beane · Domenico Orlando · Susanne Reffert
We investigate the odd-even staggering in the harmonically-trapped unitary Fermi gas at large particle-number charge $Q$ . Using both a large- $N$ BdG description and a complementary large-charge EFT method, we show that for odd particle number the extra fermion forms an edge-localized quasiparticle near the Thomas-Fermi surface rather than a bulk excitation. In the edge limit, the microscopic BdG problem reduces to a universal coupled Airy system whose lowest positive eigenvalue fixes the leading odd-even splitting energy, $χ ξ^{1/6} (24 Q)^{1/9} ℏ ω + \dots$ where $ξ$ is the Bertsch parameter, and $χ$ is a universal edge coefficient. The associated EFT describes a fermionic mode confined to the boundary and coupled to the superfluid Goldstone field, reproducing the same $Q$ scaling while introducing a dependence on two low-energy constants. Finally, we numerically compute the spectrum and confirm the predicted scaling and localization properties.
↳ cond-mat.quant-gashep-thnucl-th2 citations
08
Axial-Vector Lattice Benchmarks Reveal a Common Medium Response of Meson Screening in Hot QCD
Jie Ren🇨🇳 · Chen Chen🇨🇳 · Fei Gao🇨🇳 · Si-xue Qin🇨🇳
Meson screening masses trace the evolution of hadronic correlations toward quasi-free quark--antiquark screening in hot QCD. Combining lattice QCD (LQCD) benchmarks with a symmetry-preserving Dyson--Schwinger baseline, we identify a flavor-dependent axial-vector quasi-free onset, $x_{f g}^{*} = T_{f g}^{*} / T_{c}$ : an operational high-temperature matching scale at which the axial-vector screening mass has approached the corresponding free-field value after ordinary chiral restoration or parity-partner convergence has set in. On the finite interval $1 \leq x ≲ x_{f g}^{*}$ , independent light/strange and charm-containing lattice benchmarks are organized by a common medium-response function with one flavor-sector parameter. One axial-vector point fixes this parameter; the remaining axial-vector data test its temperature dependence, and vector screening masses validate it without vector input. A reduced-mass interpolation then yields lattice-testable quasi-free onsets and screening spectra for light-charm and bottom-containing sectors. The resulting onset scales provide common reference points for future lattice and continuum studies of meson dissolution across flavor.
↳ hep-phhep-exhep-latnucl-ex+10 citations
09
Kinetic freeze-out and diffusion dynamics in small-system asymmetric collisions at sqrt(sNN)=200 GeV in light of a generalized Fokker-Planck distribution
M. Waqas🇨🇳 · Wolfgang Bietenholz🇲🇽 · Khusniddin K. Olimov🇺🇿 · Muhammad Ajaz🇸🇦 · Jihane Ben Slimane🇸🇦 · Laila A. Al-Essa🇸🇦 · A. Haj Ismail🇦🇪
A generalized Fokker-Planck solution is used to examine the transverse momentum ( $p_{T}$ ) spectra of neutral pions generated in small-system asymmetric collisions, $p$ -Al, $p$ -Au, $d$ -Au, and $^{3}$ He-Au, at $s_{N N} = 200$ GeV. This framework provides a cohesive explanation of particle production over a broad range of transverse momenta. We extract the energy scale governing the transition between a thermal and a hard regime, the effective temperature ( $T$ ), and the exponents determining the high-momentum falloff from fits to PHENIX data. $T$ increases systematically with the collision centrality and colliding system size, ranging from about 0.33 GeV in peripheral $p$ -Al collisions to 0.45 GeV in central $^{3}$ He-Au collisions. This increase is correlated with the average number of participant nucleons, $< N_{p a r t} >$ , and the charged-particle pseudorapidity density, $< d N_{c h} / d η >$ , indicating that larger and more central collisions create a denser, more strongly interacting medium that freezes out at a higher temperature. The acquired transition scale and power-law exponents follow consistent patterns across systems and centralities, revealing details about the sharpness of the transition from thermal to hard processes, and the relative strength of momentum-space diffusion versus drag. Interestingly, when the gold target dominates the collision geometry in the largest system ( $^{3}$ He-Au), the transition scale becomes nearly independent of centrality, signifying saturation of the diffusion process. Our findings demonstrate that the generalized Fokker-Planck solution is a sensitive probe of transport properties and non-extensive dynamics in the quark-gluon plasma produced even in small-system relativistic collisions, and it consistently describes pion spectra in this set of collisions.
↳ hep-phnucl-th0 citations

Affiliations

first authorsco-authorsvia INSPIRE