Nuclear Theory·nucl-th

Wednesday·July 1, 2026

14 papers—8 primary·6 cross-listed

01
Exact Calculation of Two-neutrino Double Beta Decay Rate
Stefan-Alexandru Ghinescu🇷🇴 · Andrei Neacsu🇷🇴 · Sabin Stoica🇷🇴
The calculation of the two-neutrino double-beta decay (DBD) rates has relied so far on approximations that decouple the nuclear and atomic parts. To provide a more rigorous treatment, we propose an approach which incorporates the full interdependence between nuclear structure and lepton kinematics. Deviations of the decay rates and electron spectra from the traditional methods, such as closure, non-closure and Taylor expansion approximation, are presented and discussed for the isotopes $^{82}$ Se and $^{136}$ Xe. Our approach gives a more realistic description of the DBD process, and opens the avenue of additional, new theoretical and experimental investigations into nuclear and atomic effects in the process. Extensions of this framework to other isotopes and to neutrinoless double-beta decay are currently underway.
nucl-th0 citations
02
Symmetry energy of baryon- and neutron-rich nuclear matter
Zhi-Ying Qin🇨🇳 · Jia Zhou🇨🇳 · Jun Xu🇨🇳
Based on the relativistic mean-field model and assuming $G$ -parity invariance, we have studied the equation of state of baryon- and neutron-rich matter produced in low-energy relativistic heavy-ion collisions. Similar to the traditional isospin symmetry energy, we define the baryon-antibaryon symmetry energy characterizing the energy difference due to the baryon-antibaryon asymmetry. The potential difference between nucleons and antinucleons is correlated with the potential contribution of the baryon-antibaryon symmetry energy mainly from the vector interaction in baryon-rich matter. The isospin symmetry energy is considerably reduced even with a small fraction of antinucleons compared to the traditional case with only nucleons. A more attractive antineutron potential than antiproton potential is observed, and the isospin splitting of the mean-field potential for antinucleons is found to be intrinsically larger than that for nucleons in baryon- and neutron-rich matter.
nucl-thPLB(2026)·0 citations
03
Relativistic magnetohydrodynamics from kinetic theory
Khwahish Kushwah
This thesis develops a kinetic-theory framework for relativistic dissipative magnetohydrodynamics under strong electromagnetic fields, motivated by quark-gluon plasma in heavy-ion collisions. Starting from the relativistic Boltzmann-Vlasov equation and using the method of moments within the 14-moment approximation, it derives causal second-order hydrodynamic equations for relativistic plasmas with increasing generality. The work first review relativistic dissipative hydrodynamics and its kinetic foundations, emphasizing the need for Israel-Stewart-type transient theories to preserve causality and stability. Electromagnetic fields are then introduced at the microscopic level, where the Lorentz force modifies the moment hierarchy and produces anisotropic transport effects absent in field-free fluids. Next, it develops relativistic dissipative magnetohydrodynamics for a non-resistive two-component plasma of oppositely charged particles. Here, the magnetic field couples the dissipative sectors of the two species, generating relative dissipative currents and coupled shear dynamics. For Bjorken expansion, the theory predicts damped oscillations in the transverse shear sector associated with cyclotron motion. Finally, the thesis treats the resistive two-component case, where the electric field evolves dynamically and couples to charge diffusion and shear stress. The resulting theory reveals current-shear feedback, transient electromagnetic generation of momentum anisotropy, and underdamped dissipative oscillations. Applications to homogeneous and Bjorken-expanding plasmas show how resistive and electromagnetic effects modify evolution beyond standard hydrodynamics. Overall, the thesis extends relativistic dissipative hydrodynamics to magnetized and resistive plasmas, providing a microscopic foundation for future studies of strongly magnetized quark-gluon plasma and astrophysical systems.
nucl-thastro-ph.HEhep-thphysics.plasm-ph0 citations
04
Charged pseudoscalar mesons in a strong magnetic field under the Weinberg model
Gaoqing Cao🇨🇳
Recent lattice QCD simulations have further validated their earlier unusual findings: The lowest energies of charged pseudoscalar mesons $π^{\pm}$ and $K^{\pm}$ decrease at stronger magnetic field, though quasiparticle approximation assumes an increasing feature. We address this long-standing puzzle by employing the chiral effective Weinberg model, in which pseudoscalar and vector mesons exhibit intrinsic mutual couplings. Under this framework, charged pseudoscalar mesons deviate from pure quasiparticle behavior due to their interactions with neutral pseudoscalar and charged vector mesons. By incorporating the modifications induced by neutral pseudoscalar-charged vector loops, we demonstrate that the lowest energies of $π^{\pm}$ and $K^{\pm}$ indeed decrease at stronger magnetic field in both the lowest- and full-Landau-level calculations. However, instabilities emerge under a fixed mesonic coupling constant, and appear unavoidable when attempting to reproduce the observed peak structures. In contrast to the quark-antiquark meson description in models such as the NJL model, our results support the conjecture that a charged pseudoscalar meson could effectively form a molecular bound state of a neutral pseudoscalar meson and a charged vector meson in the strong magnetic field regime.
nucl-thhep-ph0 citations
05
Cooling of Hybrid Stars with a 2SC+ $< dd >$ Phase
Tsuneo Noda🇯🇵 · Akira Dohi🇯🇵 · Nobutoshi Yasutake🇯🇵 · Huan Chen🇨🇳 · Toshiki Maruyama🇯🇵 · Toshitaka Tatsumi🇯🇵
Recently, Fujimoto, Fukushima & Weise (2019) have proposed a new colour-superconductive state, 2SC+ $< dd >$ phase, which can be smoothly connected to the low-density baryon superfluidity in contrast to the 2SC phase. In this scenario, the neutron $^{3} P_{2}$ superfluidity on the low-density side of the phase transition is inherited by unpaired $d$ -quarks in the 2SC phase on the high-density side. Since this could be realized in hybrid stars (neutron stars containing hadronic and quark matter), the 2SC+ $< dd >$ phase may change the properties of neutron stars compared to the traditional 2SC phase. In this work, we study the thermal evolution of hybrid stars with the 2SC+ $< dd >$ phase for the first time. We find that NSs with the 2SC+ $< dd >$ phase become hotter than those with the 2SC phase, and are close to the CFL phase. The $^{3} P_{2}$ superfluidity plays an important role in cooling curves with not the 2SC but 2SC+ $< dd >$ phases due to the suppression of quark $β$ decay. We therefore point out that, if the scenario of 2SC+ $< dd >$ phase is true, it could be specified through low-temperature observations such as Vela, 3C58, Vela Jr., and Vela-like pulsar.
nucl-thastro-ph.HEPTEP(2026)·0 citations
06
Strong Evidence for Three- $α$ Clustering in the Ground State of $^{12} C$
Kazuki Yoshida · Masaaki Kimura
The ground state of $^{12} C$ has often been approximated by a mean-field picture. This conventional view has been challenged by recent nuclear theories suggesting non-negligible $α$ -cluster formation, but experimental evidence remains inconclusive. Here, we show that existing $^{12} C (p, p α)^{8} Be$ data provide direct evidence for a pronounced $α$ cluster formation in the ground state of $^{12} C$ . We analyze the data with distorted-wave impulse approximation using $α$ preformation amplitudes from an unrestricted $3 α$ cluster model and harmonic-oscillator-based models. The results show that the former reproduces the measured cross sections, whereas the latter underestimate them by more than an order of magnitude. Thus, contrary to conventional expectations, the data support a nearly fully developed three- $α$ cluster structure in the ground state of $^{12} C$ .
nucl-th0 citations
07
Nuclear excitation via inelastic scattering of low-energy vortex electrons
Jia-Lin Zhang · Zhi-Wei Lu · Mamutjan Ababekri · Yuanbin Wu · Jian-Xing Li
Vortex particles carrying orbital angular momenta (OAMs) have found important applications in broad fields. However, the experimental verification of OAM transfer at the nuclear scale remains a great challenge. Here, we put forward a novel method to probe such OAM transfer through nuclear excitation via inelastic scattering of low-energy vortex electrons. We develop a Dirac distorted-wave Born approximation framework that incorporates the incident-electron OAM and a nonperturbative treatment of the Coulomb field, and apply it to $^{229} Th$ . We find that the vortex and non-vortex electrons yield opposite angular distributions, attributed to the OAM-modified selection rule and the Coulomb-induced redistribution of partial-wave strengths, providing an angle-resolved signature. Moreover, the vortex electron exhibits topological protection in the nuclear Coulomb field. Our method offers a route to probing nuclear-scale OAM transfer and deepens our understanding of the topological properties of vortex particles.
nucl-th0 citations
08
Finite-range EFT for the $E 1$ strength distribution of $^{6}$ He
Matthias Göbel · Hans-Werner Hammer · Daniel R. Phillips
Halo effective field theory (Halo EFT) is a powerful tool to describe halo nuclei and predict low-energy observables with quantified uncertainties. However, in the case that there is a leading-order interaction determined by two or more effective-range parameters, such as the $^{2} P_{3/2}$ $n α$ interaction in $^{6}$ He, the standard implementation in the dimer formalism leads to an energy-dependent interaction. This complicates the construction of a Hilbert space of states, especially beyond the two-body problem. As an alternative, we propose the use of a finite-range formulation of Halo EFT, which avoids these complications. For definiteness, we use separable interactions with Yamaguchi-like form factors, but other choices are possible. We solve for the $^{6}$ He bound state in this finite-range EFT up to next-to-leading order (NLO) in the Halo EFT power counting and calculate the ground-state $E 1$ strength distribution of $^{6}$ He at this order. The shape of the resulting distribution agrees with that obtained in the dimer formalism of the EFT, but finite-range EFT does not require the use of a non-standard wave function normalization condition. We also calculate the root-mean-square charge radius of $^{6}$ He and find $2.06 \pm 0.35$ ~fm at LO and $2.00 \pm 0.09$ ~fm at NLO, in agreement with experimental data. To calculate the full $E 1$ strength distribution final-state interactions must be incorporated. We approximate the full-three-body scattering operator first by single Møller operators and then by products of up to three Møller operators. The resulting NLO $E 1$ strength distribution agrees with the experimental data within theory uncertainties.
nucl-th0 citations

Affiliations

first authorsco-authorsvia INSPIRE