Nuclear Theory·nucl-th

Mon·Sep 7, 2026Monday·September 7, 2026

14 papers—9 primary·5 cross-listed

01
Astrophysical $S$ -factors in primordial nucleosynthesis
Carlos A. Salas · Neelima G. Kelkar
The astrophysical $S$ -factor plays an important role in extrapolating the laboratory cross section data to lower energies of relevance in nucleosynthesis calculations. Be it empirical fits or theoretical modeling of the $S$ -factors, experimental information on the cross sections over a range of energies is essential to provide reliable $S$ -factors and thereby the nuclear reaction rates which enter the nucleosynthesis networks. In view of the scattered and sometimes diverse data on the same reaction in literature and the databases, we present a compilation and review of available data from 318 references involving 371 experiments on the leading and sub-leading reactions in big bang nucleosynthesis (BBN). Salient features such as bumps at certain energies and a steep rise in the $S$ -factor at low energies due to screening effects are found to vary in different experiments. The latter depends on the variation of targets and sometimes temperature to extract information on the same nuclear reaction. For instance, 45 cases in which the $S$ -factor at low-energy could present electron screening-effect showed deviations from background values with features which are unique to each experiment, target and temperature. The extensive compilation, discussions of the relevance of each reaction in BBN and the features of the $S$ -factors is followed by a presentation of empirical fits to the $S$ -factors in some selected reactions of interest. This is a preprint of the following work: Carlos A. Salas and Neelima G. Kelkar, Astrophysical S-Factors in Primordial Nucleosynthesis, 2026, SpringerBriefs in Physics. It is the version of the author's manuscript prior to acceptance for publication and has not undergone editorial and/or peer review on behalf of the Publisher (where applicable). The final authenticated version is available online at: https://doi.org/10.1007/978-3-032-30466-7
nucl-th
02
Breakdown of the Plane-Wave Trojan Horse Analysis of the $^{12} C +^{12} C$ Fusion Reaction: Critical Role of Coulomb Distortions
Akram Mukhamedzhanov
Recently, a new Trojan Horse Method (THM) measurement of carbon-carbon fusion was reported by Li \textit{et al.} [Phys. Lett. B (2026) 140675]. The purpose of the present work is to demonstrate the breakdown of the plane-wave approximation used in the analysis of these data and the critical role of Coulomb distortions in the initial and final states. The reaction mechanism underlying the THM analysis of the $^{12} C +^{12} C$ fusion reaction using the $^{16} O +^{12} C \to α_{s} + α +^{20} Ne$ reaction is investigated. Particular attention is paid to the spectator momentum distribution and to the dependence of the THM reaction amplitude on the relative carbon-carbon energy $E$ . It is demonstrated that agreement with the measured spectator momentum distribution does not by itself validate the plane-wave approximation. Although the experimental momentum distribution can be reproduced, inclusion of Coulomb distortions in both the initial and final channels leads to an energy dependence of the THM amplitude that is completely different from the plane-wave result. Consequently, the energy dependence of the $^{12} C +^{12} C$ fusion cross section extracted from the THM data can be strongly distorted by the plane-wave treatment. It is concluded that the astrophysical factor extracted in the plane-wave analysis cannot be regarded as reliable and may lead to misleading conclusions concerning the low-energy $^{12} C +^{12} C$ fusion reaction.
nucl-thastro-ph.SR
03
Percent-Level Prediction of the Deuteron Magnetic Polarizability
Rishi Cherukuri · Jiunn-Wei Chen · Xiangdong Ji
Working through next-to-next-to-leading order (NNLO) accuracy in pionless effective field theory, we compute the isovector magnetic-dipole contribution to the scalar deuteron magnetic polarizability. The polarizability follows from detailed balance and a dispersion integral with the two magnetic current counter-terms fixed by the thermal $n p \to d γ$ rate. The conventional $ρ$ and $Z$ expansion schemes differ by $12.3%$ at next-to-leading order but agree to $0.165%$ at NNLO, resulting an apparent scheme dependence and supplying an independent convergence diagnostic. We obtain $β_{M 0}^{(M 1_{v})} = 0.0789 \pm 0.0010 fm^{3}$ , a $1.3%$ uncertainty, compared with $4.9%$ previously.
nucl-thhep-ph
04
FUSION: a skill-based research agent for publicly obtainable nuclear-physics codes
Jin Lei
Running an unfamiliar nuclear-physics code is rarely difficult because of the physics alone. One must find and build the program, learn its input conventions, and decide whether a plausible output is actually correct. A general-purpose coding agent helps with the first two tasks but may make the last one harder: it can write an input file that runs with the wrong physical convention. FUSION addresses this problem with code-specific skills. A skill obtains the code from its public source, starts from a verified input, runs and parses the calculation, records known failure modes, and must reproduce a stated benchmark to a stated tolerance before reporting a result. The current release covers twenty codes, spanning optical models and reactions, nuclear structure, fission and statistical models, astrophysics and R-matrix analysis, and heavy-ion transport. It also includes an offline, searchable collection of 61 167 pages derived from the nucl-th literature. User notes and credentials remain outside the public repository. FUSION is available under the MIT license at https://github.com/jinleiphys/FUSION; documentation is at https://vibeinscience.com. Here I describe the design, the checks behind the current release, and one complete calculation from input to comparison with measured data.
nucl-thphysics.comp-ph
05
Rotational Feshbach resonances in the deformed halo nucleus $^{31}$ Ne
Shin Watanabe · Shoya Ogawa · Takuma Matsumoto · Kazuyuki Ogata
Background: The deformed halo nucleus $^{31}$ Ne exhibits unique structural properties arising from the interplay between its halo neutron and the deformation of the $^{30}$ Ne core. While previous studies have established the nature of its weakly-bound ground state through reaction cross sections and inclusive breakup measurements, the structure of its excited states in the low-energy continuum, which are expected to appear as resonances, remains largely unexplored. Purpose: We investigate the structure of these resonant states and clarify their rotational nature and formation mechanism. Method: The structure of $^{31}$ Ne is described using the particle rotor model (PRM), which explicitly treats the coupling between core excitation and single-particle motion in both bound and continuum states. Results: The calculations predict the emergence of unbound rotational states in the low-energy continuum of $^{31}$ Ne, which form a rotational sequence built on the weakly-bound Nilsson [321 3/2] configuration. As the total angular momentum increases along the rotational band, the intrinsic Nilsson structure is largely preserved, whereas the dominant core-spin component shifts to higher spins. These resonances are stabilized through the combined effects of coupling to higher-lying closed core-excited channels and reduced effective neutron relative energies, and can therefore be interpreted as rotational Feshbach resonances. Conclusion: The present study elucidates the formation mechanism of rotational Feshbach resonances in $^{31}$ Ne. This mechanism is expected to be a general feature of weakly-bound deformed nuclei. Exclusive breakup measurements with coincident detection of $γ$ rays from the de-exciting core will provide crucial tests of the proposed formation mechanism of rotational Feshbach resonances.
nucl-th
06
Microscopic Investigation of $α$ Clustering for the $α$ Decay Based on the Density-Constrained Frozen Hartree-Fock Calculations
Shu Yamamura · Kazuyuki Sekizawa
The inter-nucleus potential between an $α$ particle and a daughter nucleus ( $^{100}$ Sn) is calculated based on the density-constraint frozen Hartree-Fock (DCFHF) method with a Skyrme-type energy density functional (EDF). It is shown that the potential has a repulsive core at short distances with an attractive pocket close to the nuclear surface. We have confirmed that the potential obtained with the Skyrme DCFHF method agrees well with that obtained with the extended Thomas-Fermi approximation to the Skyrme EDF. Furthermore, it is demonstrated that the height of the repulsive core decreases by taking into account melting of the $α$ cluster inside a nucleus. With the aid of the nucleon localization function, we show that the obtained state in DCFHF clearly manifests localization of spin-up and spin-down neutrons and protons, suggesting the possible emergence of an $α$ -cluster-like structure in the DCFHF wave function. These results opens up a possibility to investigate $α$ clustering in heavy nuclei within mean-field calculations.
nucl-th
07
Thermal boundaries for relativistic fluids without a conserved charge
Lorenzo Gavassino · Soeren Schlichting · Gabriel S. Denicol
We study an ultrarelativistic fluid with no conserved particle number in a planar slab geometry bounded by two parallel, thermally conducting plates held at fixed (possibly different) temperatures. The fluid-wall interaction is described within kinetic theory by modeling the fluid as self-interacting radiation: a gas of bosons emitted and absorbed by the walls according to black-body laws, while mutual collisions enforce local equilibration. From this microscopic setup we derive effective boundary conditions for the hydrodynamic fields, finding that the walls behave as modified absorbing boundaries (and not as thermostats). In particular, the fluid temperature at the boundary does not generally coincide with the wall temperature. We prove that the resulting initial-boundary-value problem is well posed. When the plates are held at different temperatures, the system develops a uniform steady flow from the hotter to the colder wall, with energy density equal to the arithmetic mean of the corresponding black-body energy densities in the limit of a small temperature difference.
nucl-thhep-thphysics.flu-dyn
08
Signals for Nuclear Solid-Liquid Phase Transition in Clustering Nuclei
Xi-Guang Cao · Yong-Hao Jin · Chun-Wang Ma · Wen-Bo Liu · Yu-Gang Ma
The nuclear phase diagram remains a fundamental challenge, where uncovering how the cluster degree of freedom evolves with temperature and energy is essential to understand the intriguing crossover between cluster, nucleon, and nuclear astrophysics. A new first-order phase transition, the nuclear solid-liquid phase transition (SLPT), emerges spontaneously from nucleonic degrees of freedom in low-energy heavy-ion collisions. Clear signals of the SLPT are identified as a region of negative heat capacity in smaller systems (e.g., $^{12} C +^{12} C$ and $^{16} O +^{12} C$ ) and a caloric plateau in larger systems (e.g., $^{28} Si +^{12} C$ and $^{40} Ca +^{12} C$ ), along with prominent behaviors in the number of fragment species and information entropy. Moreover, the pairwise distance probability density function provides a direct spatial fingerprint of the melting, where long-range crystalline $α$ -cluster peaks vanish above the transition temperature, giving way to a liquid-like distribution. This new phase transition unifies the many-body dynamics of finite constituents, extending from nanoscale clusters to nuclear systems. Beyond advancing nuclear structure and phase diagrams, these insights offer profound implications for astrophysics, notably linking structural evolution to astrophysical phase transitions via nuclear cluster dissolution in supernovae.
nucl-th
09
Spectator shadowing as the source of the breaking of NCQ scaling at RHIC-FXT and FAIR energies
Tom Reichert · Iurii Karpenko
The apparent scaling of the elliptic flow of identified hadrons with the number of constituent quarks indicates the presence of quark coalescence, and in turn suggests the presence of a deconfined state in heavy-ion collisions. Recent measurements at RHIC found a breaking of NCQ scaling at low energies and suggested that this marks the onset of partonic collectivity at higher energies. Here, we present a new framework embedding the effect of spectator shadowing into the flow scaling relations. Using a toy model with an idealized quark coalescence source and a ballistic Glauber model for the bypassing spectator, we demonstrate that the observed breaking is an effect of spectator shadowing.
nucl-thnucl-ex
10
Hadronization effects and electroweak contributions in DIS one-jettiness
Radja Boughezal · Haotian Cao · Zhong-Bo Kang · Xiaohui Liu · Sonny Mantry · Frank Petriello
We study the structure of leading hadronization effects and the contributions of massive electroweak gauge boson exchange in the $τ_{1}$ and $τ_{1 a}$ 1-Jettiness global event shapes for deep inelastic scattering (DIS). The leading hadronization effects in $τ_{1}$ acquire a non-trivial dependence on the hard scattering kinematics. This kinematic dependence is explicitly calculable, so that the leading hadronization effects in $τ_{1}$ , $τ_{1 a}$ , and DIS thrust are universal and described by the same underlying shape function. The additional calculable kinematic dependence in $τ_{1}$ provides an independent lever arm for simultaneously constraining hadronization effects in these observables. We present corresponding results at the N $^{3}$ LL+ $O (α_{s}^{2})$ level of accuracy. We extend previous results by including the contributions mediated by the exchange of the massive $Z$ and $W$ electroweak gauge bosons for neutral current (NC) and charged current (CC) DIS, respectively, including $O (α_{s})$ QCD corrections to obtain N $^{2}$ LL+ $O (α_{s})$ results. We compare theoretical predictions to Pythia simulation and demonstrate the universality of leading hadronization effects across NC and CC DIS processes and a wide range of kinematics relevant to HERA and the EIC.
↳ hep-phnucl-th
11
Systematic study of baryon-baryon interactions in singly bottomed systems
Yuxuan Du · Yanyue Pan · Xinmei Zhu · Zhiyun Tan · Hongxia Huang · Jialun Ping
In this work, we systematically investigate the baryon-baryon interactions in singly bottomed dibaryon systems within the chiral quark model and search for possible bound states. By exploring the baryon-baryon interaction, we find that low-isospin channels tend to generate deeper attractive interactions and are prone to form bound states. We also find that decuplet-decuplet systems tend to show stronger attraction and support a larger number of bound states, whereas octet-octet systems generally exhibit weaker attraction and fewer bound solutions. The binding behavior of octet-decuplet systems generall lies between these two cases. Several bound states are obtained, which are $Δ Σ_{b}^{*}$ with $I J = \frac{1}{2} 0$ , $\frac{1}{2} 1$ , $\frac{1}{2} 2$ , $\frac{1}{2} 3$ , and $\frac{3}{2} 3$ , the $Δ Σ_{b}$ with $I J = \frac{1}{2} 1$ , $\frac{1}{2} 2$ , $\frac{3}{2} 1$ , and $\frac{3}{2} 2$ , the $N Σ_{b}^{*}$ with $I J = \frac{1}{2} 2$ , the $Σ Σ_{b}$ with $I J = 00$ , $01$ , and $11$ , the $Σ Σ_{b}^{*}$ with $I J = 01$ and $02$ , the $Σ^{*} Σ_{b}$ with $I J = 01$ and $02$ , and the $Σ^{*} Σ_{b}^{*}$ with $I J = 00$ , $01$ , $02$ , $03$ , and $13$ . Further investigations of the corresponding scattering processes are still required to determine whether these bound-state candidates can be identified. These states deserve further experimental investigation.
↳ hep-phhep-exhep-latnucl-th
12
Accessing the Wess-Zumino-Witten term using Lattice QCD
Fernando Romero-López · Stephen R. Sharpe
The Wess-Zumino-Witten interaction in chiral perturbation theory is a manifestation of chiral anomalies. One of its consequences is the presence of a nonvanishing $K K \to π^{+} π^{0} π^{-}$ amplitude. We derive the finite-volume formalism that allows one to access this, and related, amplitudes, using the spectra of two and three particles in finite volumes, spectra that can be calculated using lattice QCD. Specifically, we present the formalism for the systems $K K + 3 π$ with $I = 0$ and $π K + π π K$ with $I = 1/2$ and $3/2$ . In addition, we determine the threshold expansions for the $2 \leftrightarrow 3$ and $3 \leftrightarrow 3$ K matrices that enter the formalism, and calculate the leading order predictions from chiral perturbation theory for the coefficients that enter these expansions.
↳ hep-lathep-phnucl-th
13
Probing Neutron Star Equation of State Universality with Gravitational Waves
Praveer Tiwari · Ajit Kumar Mehta · K. G. Arun
Current neutron star equation-of-state inferences assume that a common equation of state describes all neutron stars. However, {poorly understood dense-matter physics may give rise to distinct long-lived stellar subpopulations following different mass--tidal-deformability relations, invalidating this assumption. In this Letter, we demonstrate that next-generation gravitational-wave observatories enable neutron star equation-of-state universality to be transformed from an assumption into a testable hypothesis. By combining hierarchical Bayesian inference with a piecewise-polytropic parametrization of the neutron star equation of state, we establish a framework for testing equation-of-state universality with next-generation gravitational-wave observatories. We find that about 30 (50) loud binary neutron star mergers with network SNRs above 100 are sufficient to provide compelling evidence for departures from equation-of-state universality, even if only 20% (10%) of the population exhibits one of the representative non-universality parametrizations considered here.
↳ gr-qcastro-ph.HEnucl-th
14
Chaos is Target-Blind in High-Energy QCD Evolution
Raktim Abir
Chaotic evolution measures how rapidly nearby configurations separate, but the existence of such rapid evolution does not by itself determine what physical information the evolution actually carries. For fixed-coupling JIMWLK evolution with fresh transverse-local, color-isotropic noise, we show that this distinction becomes exact - leading to a no go theorem. At finite rapidity step and finite transverse regulator, the exact linearized update depends on the Wilson-line background only through local adjoint rotations of fresh color-isotropic noise. Once the past is conditioned upon, these rotations leave the complete local noise measure invariant, so the tangent process has the same probability law for any target ensemble evolved with the same regulated fixed-coupling dynamics, including dilute and saturated ensembles. After the exact global color-rotation mode is removed, the reduced tangent process found to have a positive leading Lyapunov exponent which indicate chaotic evolution. Fixed-coupling JIMWLK therefor can be dynamically chaotic while its tangent-only statistics carry no information about the target ensemble. Spatially nonlocal noise however evades the argument because correlations between distinct sites leave relative Wilson lines in the conditional covariance.
↳ hep-phhep-thmath-phmath.MP+2