Nuclear Theory·nucl-th

Thursday·January 1, 2026

21 papers—10 primary·11 cross-listed

01
Fluctuations of Temperature in the Polyakov-loop extended Nambu--Jona-Lasinio Model
He Liu🇨🇳 · Peng Wu🇨🇳 · Hong-Ming Liu🇨🇳 · Peng-Cheng Chu🇨🇳
We investigate temperature fluctuations in hot QCD matter using a 3-flavor Polyakov-loop extended Nambu--Jona-Lasinio (PNJL) model. The high-order cumulant ratios $R_{n 2}$ ( $n > 2$ ) exhibit non-monotonic variations across the chiral phase transition, characterized by slight fluctuations in the chiral crossover region and significant oscillations around the critical point. In contrast, distinct peak and dip structures are observed in the cumulant ratios at low baryon chemical potential. These structures gradually weaken and eventually vanish at high chemical potential as they compete with the sharpening of the chiral phase transition, particularly near the critical point and the first-order phase transition. Our results indicate that these non-monotonic peak and dip structures in high-order cumulant ratios are associated with the deconfinement phase transition. This study quantitatively analyzes temperature fluctuation behavior across different phase transition regions, and the findings are expected to be observed and validated in heavy-ion collision experiments through measurements of event-by-event mean transverse momentum fluctuations.
nucl-thUniverse(2026)·3 citations
02
Towards a bottom-up formulation of spin kinetic theory
Zonglin Mo🇨🇳 · Yi Yin🇨🇳
We develop a bottom-up formulation of spin-kinetic theory for hot and/or dense plasmas. We introduce scalar and axial-vector phase-space functions as dynamical variables that parametrize both spin-averaged and spin-dependent distribution functions. Using spin-dependent Poisson brackets, we derive the corresponding kinetic equations and construct the associated Schwinger-Keldysh action. We further demonstrate how physical observables can be expressed in terms of these dynamical variables through constitutive relations. In the linear response regime, we establish a precise matching between the kinetic-theory and field-theory descriptions of vector and axial Wigner functions under electromagnetic and gravitational perturbations. Our framework provides a complementary approach to describing the dynamics of spin effects in a medium.
nucl-thhep-phPRD(2026)·0 citations
03
Initial spin fluctuations as a probe of cluster spin structure in $^{16} O$ and $^{20} Ne$ nuclei
Xiang Fan🇨🇳 · Jun-Qi Tao🇨🇳 · Ze-Fang Jiang🇨🇳 · Ben-Wei Zhang🇨🇳
We investigate the imprint of $α$ clustering on initial spin fluctuations in relativistic $^{16} O +^{16} O$ and $^{20} Ne +^{20} Ne$ collisions at $s_{NN} = 5.36$ ~TeV. Utilizing \textit{ab initio} configurations from Nuclear Lattice Effective Field Theory (NLEFT) and phenomenological $α$ -cluster models within a Monte-Carlo Glauber framework, we compute the event-by-event variance of the initial net spin polarization. We find that the strong short-range spin--isospin correlations characteristic of $α$ clusters lead to a significant suppression of spin fluctuations compared to a spherical Woods--Saxon baseline with uncorrelated spins. By constructing a scaled fluctuation observable that accounts for trivial finite-size effects, we demonstrate that this suppression exhibits a non-monotonic centrality dependence sensitive to the detailed cluster geometry. Furthermore, we propose the ratio of scaled spin fluctuations between $^{20} Ne$ and $^{16} O$ systems as a robust probe. Our results predict distinct percent-level deviations from the baseline for clustered nuclei, suggesting that measurements of final-state $Λ$ -hyperon spin correlations can provide novel constraints on the ground-state spin structure of light nuclei.
nucl-thhep-ph0 citations
04
Halo structure of $^{6}$ He from $ab initio$ two-nucleon spatial correlations
Mengyao Huang · Tobias Frederico · Peng Yin · Robert A. M. Basili · Patrick J. Fasano · James P. Vary
We evaluate pairwise correlations using ground state wave functions for $^{4}$ He and $^{6}$ He obtained by $ab initio$ no-core shell model calculations with the Daejeon16 nucleon-nucleon interaction plus Coulomb interaction, to characterize the structures of these two systems. We demonstrate that two-nucleon spatial correlations, specifically the pair-number operator $r^{0}$ and the square-separation operator $r^{2}$ projected on two-body spin $S$ and isospin $z$ components encode important details of the halo structure of $^{6}$ He. We also analyze the single-particle state occupancies and the two-body state occupancies for the ground state of $^{4}$ He and $^{6}$ He. Our results indicate that the two valence neutrons in the ground state of $^{6}$ He dominantly form a spin-singlet configuration. The rms pair separations between core nucleons and halo neutrons of $^{6}$ He are, on average, about 80% larger than pair separations within the swollen and off-centered " $α$ core". We show that this off-centering effect is primarily responsible for the observed increase in point-proton radius $r_{p}$ in $^{6}$ He relative to $^{4}$ He.
nucl-thPRC(2025)·3 citations
05
3D solution of the full Faddeev equations for the Nd break-up reaction without 3NF effect
Reza Ramazani-Sharifabadi · Iman Ziaeian
A recently developed three-dimensional formalism for the nucleon-deuteron breakup channel initially considered only the leading-order term of the Faddeev equations, using the nucleon-nucleon T-matrix to compute the breakup amplitude. In the present study, we extend that formalism by solving the full three-nucleon Faddeev equation without three-nucleon-force contributions in a three-dimensional approach in which momentum vectors are used directly as variables. This formalism is well suited for projectile energies in scattering processes above the pion-production threshold, where partial-wave expansions become inefficient. To treat the moving singularities of the free three-nucleon propagator, we introduce a new method that treats these singularities in a manner analogous to the simple poles appearing in the Lippmann-Schwinger equation. This approach evaluates the moving singularities directly through the center-of-mass energy of the 23-subsystem and eliminates the need to partition the q-domain into intervals. The resulting formulation opens a pathway toward a systematic investigation of the complex singularities in few-body scattering processes within the Faddeev framework.
nucl-thSci.Rep.(2026)·0 citations
06
Nuclear structure properties of $^{184 - 194}$ Pb isotopes and isomers
S. Shukla · P. C. Srivastava
In the present work, we study nuclear structure properties of the $^{184 - 194}$ Pb isotopes within the framework of the nuclear shell-model. We have performed shell-model calculations using KHH7B and KHHE interactions. We have reported results for energy spectra, electromagnetic properties such as quadrupole moment ( $Q$ ), magnetic moment ( $μ$ ), $B (E 2)$ , and $B (M 1)$ transition strengths, and compared the shell-model results with the available experimental data. The shell-model results for the half-lives and seniority quantum numbers ( $v$ ) are also reported for the isomeric states.
nucl-thnucl-exNPA(2026)·1 citation
07
Dilepton emission as a novel probe of QCD critical point
Gaoqing Cao🇨🇳 · Xiaofeng Luo🇨🇳 · Weijie Fu
In this work, we propose dilepton emission rate (DER) as a sensitive probe of QCD critical point based on the extended Polyakov-quark-meson model. The model could successfully capture two main mechanisms for dilepton production, $π^{\pm}$ and quark-antiquark annihilations on one hand, and self-consistently account for chiral transition and (de-)confinement on the other hand. Along the chemical freezeout lines, all the moments of the DER peak show similar extremal features as those of light quark mass, thus the DER can well reflect the change of chiral symmetry and criticality. More importantly, the DER can be directly measured in heavy ion collisions: Compared to the baryon number fluctuations, the DER fluctuations are found to be more drastic in the critical region and more sensitive to the relative location of the critical point. However, recent statistics of DER in heavy ion collision is not large enough to perform event-by-event measurement, instead we propose to study the baseline subtracted DER: For a given dilepton center of mass, the largest deviation shows up around the point where the light quark mass fluctuation is the strongest.
nucl-th1 citation
08
$S$ -wave $K N$ scattering in a renormalizable chiral effective field theory
Xiu-Lei Ren🇨🇳
We investigate the $s$ -wave $K N$ scattering up to next-to-leading order within a renormalizable framework of covariant chiral effective field theory. Using time-ordered perturbation theory, the scattering amplitude is obtained by treating the leading-order interaction non-perturbatively and including the higher-order corrections perturbatively via the subtractive renormalization. We demonstrate that the non-perturbative treatment is essential, at least at lowest order, in the SU(3) sector of $K N$ scattering. Our NLO study achieves a good description of the empirical $s$ -wave phase shifts in the isospin $I = 1$ channel. An analysis of the effective range expansion yields a negative effective range, consistent with some partial wave analyses but opposite in sign to earlier phenomenological summaries. For the $I = 0$ counterpart, the $K N$ interaction is found to be rather weak and exhibits large uncertainties. Further low-energy $K N$ scattering experiments and lattice QCD simulations are needed to better constrain both $s$ -wave channels.
nucl-thhep-phPRD(2026)·1 citation
09
Non-Equilibrium Dynamics in QCD and Holography
Matthias Kaminski🇺🇸
The plasma generated in heavy ion collisions goes through different phases in its time evolution. While early times right after the collision are governed by far-from equilibrium dynamics, later times are believed to be well described by near-equilibrium dynamics. While the regimes of non-equilibrium are prohibitively complicated to describe within QCD, effective descriptions such as hydrodynamics provide a viable approach. In addition, holographic descriptions allow access to the full non-equilibrium dynamics at strong coupling. In this presentation, we review three examples of such hydrodynamic approaches and corresponding holographic descriptions: 1) non-equilibrium shear viscosity, 2) propagation of non-equilibrium sound waves, and 3) the non-equilibrium chiral magnetic effect.
nucl-thhep-thnucl-exJ.Subatomic Part.Cosmol.(2026)·3 citations
10
Dissipative corrections to the particle momentum spectrum of a decoupling fluid
Francesco Becattini🇮🇹 · Daniele Roselli🇮🇹 · Xin-Li Sheng🇮🇹
We present an \emph{ab initio} calculation within quantum statistical field theory and linear response theory, of the dissipative correction to the momentum spectrum of scalar particles emitted at decoupling (freeze-out) from a relativistic fluid assuming the initial state to be in local thermodynamic equilibrium. We obtain an expansion of the Wigner function of the interacting quantum field in terms of the gradients of the classical thermo-hydrodynamic fields - four-temperature vector and reduced chemical potential - evaluated on the initial local-equilibrium hypersurface, rather than on the decoupling (freeze-out) hypersurface as usual in kinetic theory. The gradient expansion includes an unexpected zeroth order term depending on the differences between thermo-hydrodynamic fields at the decoupling and the initial hypersurface. This term encodes a memory of the initial state which is related to the long-distance persistence of the correlation function between Wigner operator and stress-energy tensor and charged current that is discussed in detail. We address the phenomenological implications of these corrections for the momentum spectra measured in relativistic nuclear collisions.
nucl-thcond-mat.stat-mechhep-th1 citation
11
Mass and coupling magnetic field dependence in a scalar theory with charged bosons from an environmentally friendly renormalization group analysis
Alejandro Ayala🇲🇽 · Flávia Fialho🇧🇷 · Ana Mizher🇧🇷
We compute the running of the mass of a neutral boson and of its self-coupling in a simple model describing the self-interaction of three scalars, one of them neutral and the other two electrically charged, subject to the effects of a magnetic field, as functions of the field strength, at one-loop order. We resort to the Environmentally Friendly Renormalization Group approach, where the flow variable is taken as that describing the environmental conditions, in this case the strength of the magnetic field. We find the magnetic field dependent mass and coupling beta functions and use them to set up the differential equations satisfied by the neutral scalar mass and coupling. We solve the resulting system of coupled equations both numerically, and also analytically in the small-mass approximation. We find that the neutral scalar mass increases, while the coupling decreases with increasing field strength. The study is intended to set up the ideas to later use them in more sophisticated theories such as QED and QCD.
↳ hep-thhep-phnucl-thPRD(2026)·3 citations
12
Origin of hadron mass from gravitational D-form factor and neutron star measurements
Mamiya Kawaguchi🇨🇳 · Masayasu Harada🇯🇵 · Yong-Liang Ma🇨🇳
Clarifying the origin of hadron mass is one of the fundamental problems in particle physics, relevant from hadronic scales to astrophysical observations. At low energies, this issue is reflected in the decomposition of the hadron mass into chiral-variant and -invariant components. In this letter, we propose a method to extract the chiral invariant mass from the gravitational $D$ -form factor under the assumption of the lightest-sigma meson dominance. Focusing on the nucleon, we show that a sizable chiral invariant mass is required to reproduce lattice QCD data, consistent with neutron star constraints.
↳ hep-phhep-latnucl-thPLB(2026)·4 citations
13
Landau-Zener-Stückelberg-Majorana dynamics of magnetized quarkonia
Ahmad Jafar Arifi🇯🇵 · Kei Suzuki🇯🇵
The mass spectrum of hadrons in magnetic fields features avoided level-crossing structures arising from the mixing of spin eigenstates. In this work, we investigate the impact of level-crossing dynamics of charmonia subjected to time-dependent magnetic fields, where we particularly focus on the occupation probabilities of two or more states as they undergo transitions at avoided crossings. Using a static spectrum of charmonia in magnetic fields, we construct a multi-channel Landau-Zener Hamiltonian. Within this framework, we analyze the time evolution under several representative magnetic-field profiles, including linear ramps and Gaussian decays corresponding to single-passage dynamics, as well as Gaussian pulses realizing double-passage dynamics, and compute the occupation probabilities over a wide range of sweep rates and initial conditions. Our results show that nonadiabatic dynamics, including Landau-Zener transitions and Stückelberg interference, strongly influences the occupation probabilities of charmonia. These findings provide new insights into the real-time dynamics of magnetized hadrons and offer useful guidance for future lattice simulation studies.
↳ hep-phnucl-thPRD(2026)·2 citations
14
Total Gluon Helicity Contribution to the Proton Spin from Lattice QCD
Dian-Jun Zhao🇨🇳 · Long Chen🇨🇳 · Hongxin Dong🇨🇳 · Xiangdong Ji🇺🇸 · Liuming Liu🇨🇳 · Zhuoyi Pang🇵🇱 · Andreas Schäfer🇩🇪 · Peng Sun🇨🇳 · Yi-Bo Yang🇨🇳 · Jian-Hui Zhang🇨🇳 · Shiyi Zhong🇨🇳
We report a state-of-the-art lattice QCD calculation of the total gluon helicity contribution to the proton spin, $Δ G$ . The calculation is done on ensembles with three different lattice spacings $a = {0.08, 0.09, 0.11}$ fm. By employing distillation and momentum smearing for proton external states, we extract the bare matrix elements of the topological current $K^{μ}$ using 5-HYP smeared Coulomb gauge fixing configurations. Furthermore, we apply a non-perturbative $RI/MOM$ renormalization scheme augmented by the Cluster Decomposition Error Reduction (CDER) technique to determine the renormalization constants of $K^{μ}$ . The results obtained from different components $K^{t, i}$ (with $i$ being the direction of proton momentum or polarization) are consistent with Lorentz covariance within uncertainties. After extrapolating to the continuum limit, $Δ G$ is found to be $Δ G = 0.231 (17)^{sta.} (44)^{sym.}$ at the $MS$ scale $μ^{2} = 10 GeV^{2}$ , which constitutes approximately $46 (9) %$ of the proton spin.
↳ hep-lathep-phhep-thnucl-ex+12 citations
15
Big Bang Nucleosynthesis results refined via the Trojan Horse Method
Roberta Spartà🇮🇹 · Rosario Gianluca Pizzone🇮🇹 · Livio Lamia🇮🇹 · Alessandro Alberto Oliva🇮🇹 · Marco La Cognata🇮🇹 · Alessia Di Pietro🇮🇹 · Pierpaolo Figuera🇮🇹 · Giovanni Luca Guardo🇮🇹 · Marco La Commara🇮🇹 · Dario Lattuada🇮🇹 · Marco Mazzocco🇮🇹 · Sara Palmerini🇮🇹 and 4 other authors
This work presents the Trojan Horse Method (THM) as a powerful technique for measuring nuclear reaction cross sections at astrophysical energies. We then explore the impact of THM-derived reaction rates on the predictions of Standard Big Bang Nucleosynthesis (SBBN) using the PRIMAT code. Primordial abundances are shown for the single rate impact and, for the first time, also for all the THM rates together. The result shows significant differences with the use of THM rates, which in some cases goes in the direction of improving the agreement with the observations with respect to the use of only reaction rates from direct data, especially for the $^{7}$ Li and deuterium abundances, which are still open issues for SBBN.
↳ nucl-exastro-ph.COnucl-th0 citations
16
$D^{*} π$ interaction from the lineshape of $D_{1} (2420)$ in $B$ -decays
Pedro Brandão🇧🇷 · Breno Agatão🇧🇷 · Luciano M. Abreu🇧🇷 · K. P. Khemchandani🇧🇷 · A. Martínez Torres🇧🇷
We present a model calculation to reproduce the differential mass distribution for the $D^{*} π$ system in the reactions $B^{-} \to D^{*+} π^{-} π^{-}$ and $B^{+} \to D_{s}^{+} D^{*-} π^{+}$ analyzed by the LHCb Collaboration, which shows a dominant signal for $D_{1} (2420)$ . %\textbf{We} (The idea is to) We consider a model based on coupled channel meson-meson interactions that can describe the properties of $D_{1} (2420)$ in terms of the underlying dynamics, use it to determine the invariant mass distribution of the $D^{*} π$ system, and compare the results with the experimental data. We also determine the $D^{*} π$ scattering length, for which different values are available from different sources, leading to a controversy. To our knowledge, this is the first attempt to reproduce the mentioned data using model calculations. Our formalism relies on the hadronization of different mesons through a weak decay, allowing for the final-state (strong) interactions among the relevant constituents. We benefit from our previous work when obtaining the amplitudes corresponding to the strong interactions. We hope that our findings can be useful in further investigations of the properties of $D_{1} (2420)$ .
↳ hep-phnucl-thPLB(2026)·3 citations
17
Geometric phase from encircling an exceptional point of a quantum resonance in the complex-scaling method
Okuto Morikawa🇯🇵 · Shoya Ogawa🇯🇵 · Soma Onoda🇯🇵
Non-Hermitian operators are now routinely used to describe few-mode systems such as optical resonators and superconducting qubits, and exceptional points (EPs) are defective spectral singularities of such non-Hermitian operators. In contrast, the scattering-theoretic formulation of EP physics for unbounded Hamiltonians remains less settled. In this work, we formulate the geometric phase associated with encircling an EP when the underlying eigenstates are quantum resonances within a one-dimensional scattering model. To do this, we employ the complex-scaling method, where resonance poles of the S matrix are realized as discrete eigenvalues of the non-Hermitian dilated Hamiltonian, to construct situations in which resonant and scattering states coalesce into an EP in the complex energy plane, that is, the resonance pole is embedded into the continuum spectrum. We analyze the self-orthogonality in the vicinity of an EP, the Berry phase, and the Chern characteristic. Our results clarify how EP branch structure and geometric holonomy arise directly from resonance poles in scattering theory, thereby connecting non-Hermitian spectral topology with the traditional theory of quantum resonances.
↳ quant-phhep-thnucl-thPRA(2026)·2 citations
18
Causality constraints and anisotropic states
Raphael E. Hoult🇨🇦
We investigate the effects of anisotropy on dispersion relations and convergence in relativistic hydrodynamics. In particular, we show that for dispersion relations with a branch point at the origin (such as sound modes), there exists a continuum of collisions between hydrodynamic modes at complex wavevector. These collisions are then explicitly demonstrated to be present in a holographic plasma. We lay out a criterion for when the continuum of collisions affects the convergence of the hydrodynamic derivative expansion. Finally, the radius of convergence of hydrodynamic dispersion relations in anisotropic systems is bounded from above on the basis of compatibility with microscopic causality.
↳ hep-thnucl-th3 citations
19
QCD Wehrl and entanglement entropies in a gluon spectator model at small- $x$
Gabriel Rabelo-Soares🇧🇷 · Reinaldo Francener🇧🇷 · Gabriel S. Ramos🇧🇷 · Giorgio Torrieri🇧🇷
Recent studies have shown that hadronic multiplicity in deep inelastic scattering can be associated with entanglement entropy. However, such definitions are intrinsically longitudinal and do not capture the full phase-space structure of the proton. In this work, we investigate the proton Wehrl entropy constructed from the gluon Husimi distribution, which provides a positive phase-space description within the present definitions and model calculations. Within this framework, we employ a gluon light-front spectator model based on soft-wall AdS/QCD-inspired wave functions, with free parameters constrained by global NNPDF fits, allowing us to compute both parton distribution functions and Wigner distributions. The Husimi distribution is obtained via Gaussian smearing of the Wigner distribution with width given by the saturation scale in the GBW model. We show that from a normalized Husimi distribution one can decompose the Wehrl entropy into an entanglement entropy term and a residual term associated with transverse degrees of freedom. Numerical results for the proton entanglement entropy are shown and compared with CMS data, while the Wehrl entropy is presented for different values of the virtuality.
↳ hep-phnucl-thPRD(2026)·2 citations
20
Description of the baryon mass spectrum by open strings and diquarks
Yuki Fujimoto🇯🇵
We analyze the mass spectra of hadrons and demonstrate that the physical spectra of mesons and baryons are well described by the exponential spectrum of open strings. The open-string spectrum, derived from string theory, is characterized by a unique Hagedorn temperature $T_{H}$ and free from any other parameters. Notably, our fitting to the physical spectra yields consistent values for both mesons and baryons, $T_{H} ≃ 0.34 GeV$ , which contrasts with previous phenomenological analyses that suggested different values. This obtained value aligns well with typical string tension derived from lattice-QCD calculations and the Regge slope. In the baryonic sector, our results indicate that diquarks play a crucial role in describing the mass spectrum, implying that baryons can be understood as a quark-diquark system, as anticipated by Regge phenomenology. These findings have significant implications for our understanding of quark deconfinement, especially in the possibly existing regime at high temperature and small baryon chemical potential within the QCD phase diagram.
↳ hep-phnucl-thPRD(2026)·2 citations
21
Valence quark distribution of the pion inside a medium with finite baryon density: A Nambu--Jona-Lasinio model approach
Ashutosh Dwibedi🇮🇳 · Satyajit Puhan🇮🇳 · Sabyasachi Ghosh🇮🇳 · Harleen Dahiya🇮🇳
We calculate the in-medium valence quark distribution of the pion immersed in a finite baryon density using the light-cone quark model. The medium-modified pion properties are obtained by using the constituent quark mass-dependent light cone wave functions. To obtain the constituent quark masses at finite baryon density, we employ the two-flavor Nambu--Jona-Lasinio model. We primarily focus on the in-medium electromagnetic form factor, distribution amplitude, and the parton distribution function of the pion. The parton distribution functions are also evolved from the model scale to a perturbative scale using next to leading order Dokshitzer-Gribov-Lipatov-Altarelli-Parisi evolution equations. Furthermore, our calculated form factors are compared with available experimental measurements and lattice quantum chromodynamics studies. We also examine the Mellin moments derived from our parton distribution functions in comparison with existing extractions and theoretical model predictions.
↳ hep-phnucl-thPTEP(2026)·3 citations

Affiliations

first authorsco-authorsvia INSPIRE