Nuclear Theory·nucl-th

Tuesday·June 30, 2026

21 papers—12 primary·9 cross-listed

01
Investigating forward-backward asymmetry in D-meson production and anisotropic flow in p-Pb collisions at the LHC
Siyu Tang🇨🇳 · Chao Zhang🇨🇳 · Liang Zheng🇨🇳 · Renzhuo Wan🇨🇳 · Zi-Wei Lin🇺🇸 · Guo-Liang Ma🇨🇳
We investigate the forward--backward asymmetry in the production and elliptic flow of prompt D0 mesons in proton--lead (p--Pb) collisions at $s_{NN} = 8.16$ TeV using the heavy-flavor improved string-melting version of the AMPT model. The model calculations provide a simultaneous description of nuclear modification factor $R_{pPb}$ and $v_{2}$ in forward and backward rapidities. We find that the observed asymmetry arises from the interplay of initial-state cold nuclear matter effects and final-state partonic interactions, with the competition between coalescence and fragmentation playing a critical role in shaping the transverse momentum and rapidity dependence of both observables. This work suggests that a partonic medium is formed in high-multiplicity p-Pb collisions at LHC energies.
nucl-thhep-ph0 citations
02
Ab initio $α$ - $α$ scattering with high-fidelity chiral interactions
Avik Sarkar · Serdar Elhatisari · Timo A. Lähde · Ulf-G. Meißner
Low-energy $α$ - $α$ scattering underlies stellar helium burning and sharply tests nuclear forces in the reaction regime. We present its first calculation using the high-fidelity N3LO chiral NLEFT interaction, incorporated through wave function matching, on a fine lattice, using the adiabatic projection method. On the fine lattice, the two-cluster norm matrix becomes severely ill-conditioned, and its direct inversion is unstable. We address this with Tikhonov regularization, extrapolating the regulator to zero, and confirm the result with an independent truncated singular-value decomposition. The S- and D-wave phase shifts agree with empirical analyses, extending the validation of this interaction from bound states and charge radii to scattering and providing a practical route to ab initio nuclear reactions on fine lattices
nucl-thhep-lat2 citations
03
Revisiting identified-particle $p_{T}$ spectra using the Boltzmann-Gibbs blast-wave model in a Bayesian inference framework
Z. Xie🇨🇳 · W.Z. Li🇨🇳 · J.Q. Tao🇨🇳 · H. Zheng🇨🇳 · W.C. Zhang🇨🇳 · W. Dai🇨🇳 · L.L. Zhu🇨🇳 · X.Q. Liu🇨🇳 · D.M. Zhou🇨🇳 · B.H. Sa🇨🇳
We perform a Bayesian analysis of transverse momentum ( $p_{T}$ ) spectra of identified particles, i.e., pions, kaons, and protons, at midrapidity in Au+Au collisions and Pb+Pb collisions using the Boltzmann-Gibbs blast-wave (BGBW) model. We investigate whether it is possible to simultaneously describe the $p_{T}$ spectra of identified particles without imposing the particle species-dependent $p_{T}$ fit ranges -- a practice that was followed in conventional blast-wave model studies to achieve reasonable simultaneous fits. Using Bayesian analysis, our results indicate that a simultaneous description of the $p_{T}$ spectra of pions, kaons, and protons is feasible without imposing the particle species-dependent $p_{T}$ fit ranges, for Au+Au collisions up to the available data ( $\sim$ 2 GeV/c) and for Pb+Pb collisions up to 3 GeV/c. The extracted parameters remain broadly consistent with those obtained from conventional BGBW simultaneous fits, while the extension of the fit range leads to moderate changes in some parameters. Furthermore, Bayesian analysis yields well-constrained posterior distributions for the kinetic freeze-out temperature $T_{k in}$ , the average transverse flow velocity $⟨ β_{T} ⟩$ , and the exponent of the velocity profile $n$ and shows their correlations transparently. We suggest that the BGBW model in a Bayesian inference framework proposed can be applied in future data analyses to simultaneously describe the $p_{T}$ spectra of identified particles and extract the relevant information about the collision system.
nucl-thhep-ph0 citations
04
Embedded Random Matrix Ensembles to Statistical Shell Model: Operation of $q$ -normal forms
V.K.B. Kota · N.D. Chavda · Manan Vyas
Embedded random matrix ensembles operating in nuclear shell model spaces, with nucleons occupying a finite set of single particle orbits and interacting via a two-body interaction, form the basis for statistical shell model. With sufficiently strong interaction, the level densities in shell model spaces take close to a Gaussian form and transition strength distributions close to a bivariate Gaussian form. In practice, partitioning via spherical configurations ( $m ~$ ) and angular momentum $J$ (also isospin where appropriate) are essential. The resulting statistical spectroscopy or statistical shell model was applied successfully in the past in some studies of nuclear level densities, orbit occupancies, $β$ -decay matrix elements and so on. Going beyond these, recently it is recognized that embedded ensembles, in a better approximation, generate in-fact $q$ -normal form ( $q = 1$ gives Gaussian and $q = 0$ Wigner's semi-circle) for density of eigenvalues, bivariate $q$ -normal form for transition strengths and conditional $q$ -normal form for strength functions. These then allow us to develop statistical shell model with $q$ -normal forms. These new developments in embedded ensembles and statistical shell model are briefly reviewed in this paper. Also described, using some examples, is the role of the $q$ parameter in generating statistical properties of general quantum many-particle systems.
nucl-thquant-ph0 citations
05
Quartet Structure Above $^{100}$Sn and $^{132}$Sn Doubly Magic Isotopes
S.A. Pencu · D.S. Delion
We calculate energy levels and B(E2) values for the $\alpha$-like nuclei $^{104}$Te and $^{136}$Te. Their energy structure is described within a Multi Step Shell Model (MSM) type approach by coupling proton-proton (pp), neutron-neutron (nn) and proton-neutron(pn) phonon states over the doubly magic nuclei $^{100}$Sn and $^{132}$Sn, respectively. We also compute the electric transitions for A = 102 and A = 134 Sn, Sb and Te nuclei, described within the Tamm-Dankoff Approach (TDA) with multipole-multipole residual interaction. The encountered similarities concerning the B(E2) values and wavefunctions of the coupled states corresponding to $^{104}$Te and $^{136}$Te are analyzed.
nucl-th0 citations
06
Quark and hybrid stars with renormalization group improvement of NNLO perturbative QCD
Loïc Fernandez🇫🇮 · Jean-Loïc Kneur🇫🇷 · Marcus Benghi Pinto🇧🇷 · Constança Providência🇵🇹 · Claudia Ratti🇺🇸 · Tulio E. Restrepo🇺🇸
Recently, the NNLO perturbative QCD pressure of cold and dense symmetric matter, with arbitrary quark masses, has been resummed within the renormalization-group-optimized perturbation theory (RGOPT) framework. By being imbued with renormalization group properties, the resulting pressure is less sensitive to renormalization scale ( $Λ \equiv X μ_{B} /3$ ) variations than the NNLO perturbative QCD pressure. Here, we extend this by considering $β$ -equilibrium and charge neutrality to evaluate the corresponding equation of state (EoS). We provide a compact ``pocket" fitting formula for the EoS for $N_{f} = 2 + 1$ massive quarks at different renormalization scale parameter ( $X$ ) values. We describe pure quark stars as well as hybrid stars with quark-cores. Pure quark stars compatible with astrophysical observations were obtained with $X = 3.08 - 3.58$ , whereas a larger value (4.10) is needed if the low mass object of the observation GW190814 represents a neutron star. Hybrid stars were built considering three representative hadron models based on a relativistic mean-field description, and chosen to produce soft and stiff EoSs. Stable hybrid stars with masses compatible with the massive pulsar PSR J0740+6620 were obtained considering $X$ of the order of 2 to 2.60-2.98, the largest scale giving rise to hybrid stars with a large quark core with a radius of 5 to 8 km, and the smallest to a small quark core at the center of the star.
nucl-thastro-ph.HEhep-phhep-th0 citations
07
Nuclear equation-of-state at high density and multi-messenger astronomy: contribution of heavy-ion collisions
A. Le Fèvre🇩🇪
In the past decades, heavy-ion collisions (HIC) at intermediate energies have allowed to probe the nuclear equation-of-state (EoS) of both symmetric and asymmetric nuclear matter over a broad range of densities. In particular, flow has proven to be a powerful observable. Combining the symmetry energy and the symmetric nuclear matter constraints of the EoS from HIC allowed to predict a density dependence of the pressure in a neutron star, up to about 2.5 times saturation density ( $n_{s a t}$ ), which agrees with recent astronomical measurements deduced from gravitational waves and pulsar observations. So far, the accuracy from HIC expectations is comparable to the latter up to 1.5 $n_{s a t}$ . In these studies, a fundamental aspect is the determination of the profile of densities that are probed by experimental observables used to constrain the EoS. In the near future, new experiments like ASY-EOS performed at higher incident energy and with better accuracy will push further the frontier of the knowledge of the symmetry energy at higher density. These efforts cannot be conclusive without a reliable uncertainty determination, which is related to the reliability of transport model dependencies. Improvements and breakthroughs in transport model simulations and nuclear theory are therefore expected in a joint effort towards HIC contributions to the field of neutron-star physics, including the contribution of strangeness and of the QCD phase transition.
nucl-thastro-ph.HEnucl-ex1 citation
08
Anisotropic hadronic rescattering and its impact on $K^{* 0}$ yield, and polarization observable
Kadambini Menduli🇮🇳 · Md. Nasim🇮🇳
In this work, we investigate the anisotropic suppression of reconstructed $K^{* 0}$ resonances arising from hadronic rescattering using the A Multi-Phase Transport (AMPT) model for Au+Au collisions at $s_{N N} = 200$ GeV. We demonstrate that the rescattering probability of the decay daughters depends strongly on the decay angle $θ^{*}$ due to Lorentz boost effects, which lead to smaller laboratory-frame momenta for daughters emitted opposite to the parent particle motion. This anisotropic suppression influences several experimentally measured observables. We show that the reconstructed $K^{* 0}$ yield exhibits a strong $θ^{*}$ dependence. Furthermore, the anisotropic loss of resonances modifies the angular distributions used to extract the spin alignment parameter $ρ_{00}$ in the production-plane and helicity frames. Even in the absence of intrinsic polarization in the model, the reconstructed $K^{* 0}$ sample shows deviations of $ρ_{00}$ from the unpolarized value of $1/3$ , with opposite trends in the two reference frames. These results demonstrate that hadronic rescattering can generate apparent polarization signals and must be carefully considered in experimental measurements of vector-meson spin alignment using production plane and helicity frame.
nucl-thhep-phPRC(2026)·0 citations
09
Interplay of quadrupole and octupole degrees of freedom in the Gd isotopes
R. Budaca · S. Pascu
A systematic theoretical investigation of the quadrupole and octupole collective properties across the Gd isotopic chain is performed employing a quadrupole-octupole axially symmetric model. These nuclei have recently attracted significant attention following the revelation that the maximum octupole collectivity in this region is located at $^{150}$ Gd. The model parameters are optimized by fitting to the low-lying positive and negative-parity energy levels, as well as to known $E 0$ , $E 1$ , $E 2$ , and $E 3$ transition strengths. Our primary objective is a simultaneous and unified description of quadrupole and octupole collectivity across the even-even Gd nuclei in the $84 ⩽ N ⩽ 96$ range, a region that includes the transition from spherical to rotational nuclear shapes. The results show a smooth evolution of the quadrupole deformation, highlighted by a distinct jump at the well-known $N = 90$ critical point. The enhancement of quadrupole deformation is also correlated with the loss of non-zero octupole deformation, which is reported only for the lightest $^{148, 150}$ Gd nuclei. This translates into a fair agreement with the measured $E 3$ strength, predicting a maximum $B (E 3)$ value for the $^{152}$ Gd isotope.
nucl-thPRC(2026)·2 citations
10
Construction of Nuclear Covariant Energy Density Functional from A Physics-Guaranteed Neural Network Approach
W. F. Li · Z. M. Niu · H. Z. Liang · Y. F. Niu · B. H. Sun
Density functional theory is a practical approach for solving quantum many-body problems with available computational resources. The complexity of the nuclear force makes constructing an accurate nuclear energy density functional much more challenging. The feasibility of constructing a nuclear covariant energy density functional with deep neural networks is demonstrated. This physics-guaranteed neural network approach achieves high accuracy in predicting nuclear energy density and exhibits significantly better extrapolation abilities than traditional machine learning methods for binding energies. When combined with the existing covariant density functional, the neural network approach improves the binding energy accuracy from $644$ keV to $86$ keV in the known region and also effectively captures the microscopic shell effect. Furthermore, its extrapolation performance is also significantly enhanced, achieving an accuracy of approximately $5$ MeV even when extrapolating up to $30$ steps. This work paves the way for the construction of accurate nuclear energy density functionals through machine learning.
nucl-thPLB(2026)·0 citations
11
Bayesian Analysis with Markov Chain Monte Carlo for Global Optimization and Degeneracy Diagnosis in Nuclear Mass Models
Xiangnan Lee · Yi Hua Lam · Zi-Ao Zhang · Jayke Ren
We employ a full Bayesian analysis with adaptive Metropolis-Hastings Markov chain Monte Carlo (BA-MCMC) sampling to systematically study the posterior probability distributions of the strengths of energy terms in optimized nuclear mass models of Bethe-Weizsäcker variants. Strong correlations of some energy terms for some mass models are revealed through the parameter degeneracy diagnosis. We analyze selected refined models to determine parameter degeneracies while proposing a new macroscopic-microscopic mass model, BWL, which considers quadrupole and high-multipole deformation and shell corrections. All mass models in this work are analyzed and optimized through the BA-MCMC method. Compared with 2242 precise experimental binding energies of AME2020, BWL produces a root-mean-square deviation of 759 keV, particularly improving the description of masses in the light-nuclei and actinide regions. BA-MCMC offers robust inference on parameter degeneracy while providing an optimization method for future nuclear mass models.
nucl-thnucl-ex0 citations
12
Nonequilibrium Andreev transport at the QGP-2SC interface
Tingyu Zhang🇨🇳 · Honoka Hoshino🇯🇵 · Hiroyuki Tajima🇯🇵 · Motoi Tachibana🇯🇵 · Mariusz Sadzikowski🇵🇱
We discuss a nonequilibrium Andreev reflection at an interface between quark-gluon plasma (QGP) and two-flavor color superconducting (2SC) quark matter. Based on the Schwinger-Keldysh framework and a relativistic tunneling model, we evaluate the momentum-resolved tunneling current generated by a chemical-potential bias between the QGP and 2SC phases. We find that the Andreev reflection appears as at the fourth order of the tunneling strength, in which an incident quark in QGP is converted into a reflected hole, while a Cooper pair is injected into the 2SC condensate. We show that the Andreev reflection is enhanced when the bias becomes comparable to the gap and is suppressed in the supergap region, which is similar to that in superconducting materials. The present formulation provides a field-theoretical pathway to strongly-correlated transport across dense-matter interfaces relevant to nonequilibrium dynamics in compact stars.
nucl-thastro-ph.HEcond-mat.supr-con0 citations

Affiliations

first authorsco-authorsvia INSPIRE