Nuclear Theory·nucl-th

Friday·February 13, 2026

17 papers—6 primary·11 cross-listed

07
[Submitted on 30 Jan 2026] (cross-list from physics.comp-ph)
Addressing the ground state of the deuteron by physics-informed neural networks
Lorenzo Brevi · Antonio Mandarino · Carlo Barbieri · Enrico Prati
Machine learning techniques have proven to be effective in addressing the structure of atomic nuclei. Physics $-$ Informed Neural Networks (PINNs) are a promising machine learning technique suitable for solving integro-differential problems such as the many-body Schrödinger problem. So far, there has been no demonstration of extracting nuclear eigenstates using such method. Here, we tackle realistic nucleon-nucleon interaction in momentum space, including models with strong high-momentum correlations, and demonstrate highly accurate results for the deuteron. We further provide additional benchmarks in coordinate space. We introduce an expression for the variational energy that enters the loss function, which can be evaluated efficiently within the PINNs framework. Results are in excellent agreement with proven numerical methods, with a relative error between the value of the predicted binding energy by the PINN and the numerical benchmark of the order of $1 0^{- 6}$ . Our approach paves the way for the exploitation of PINNs to solve more complex atomic nuclei.
Subjects:
Computational Physics (physics.comp-ph); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
2602.11193 [pdf]
1 citation
08
[Submitted on 11 Feb 2026] (cross-list from hep-ph)
Pion $β$ decay and $τ \to π π ν_{τ}$ beyond leading logarithms
Vincenzo Cirigliano🇺🇸 · Martin Hoferichter🇨🇭 · Nicola Valori🇺🇸
The consistent matching of short-distance contributions and hadronic matrix elements is crucial for precise predictions of weak processes involving hadrons. In this Letter, we address this point for charged-current processes involving two pions -- pion $β$ decay $π^{\pm} \to π^{0} e^{\pm} ν_{e}$ and hadronic $τ$ decays $τ^{\pm} \to π^{\pm} π^{0} ν_{τ}$ -- whose decay rates depend on the so-called $γ W$ box correction. Using recent results from lattice QCD, we show how to formulate the matching beyond leading-logarithmic accuracy, in particular, how to cancel the dependence on the scheme choice for evanescent operators. As main results, we obtain a prediction for the decay rate of pion $β$ decay with theory uncertainties improved by a factor of three, which renders theory uncertainties negligible for future determinations of $V_{u d}$ even beyond the reach of the PIONEER experiment, and an evaluation of isospin-breaking corrections to $τ \to π π ν_{τ}$ with negligible uncertainty from the short-distance matching, as necessary for a future $τ$ -based determination of the hadronic-vacuum-polarization contribution to the anomalous magnetic moment of the muon.
Comments:
13 pages, 2 figures; journal version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2602.11253 [pdf]
PRL(2026)·10 citations
09
[Submitted on 11 Feb 2026] (cross-list from hep-lat)
Nucleon Parton Distribution Functions from Boosted Correlations in the Coulomb gauge
Xiang Gao🇺🇸 · Jinchen He🇺🇸 · Joshua Lin🇺🇸 · Swagato Mukherjee🇺🇸 · Peter Petreczky🇺🇸 · Rui Zhang🇺🇸 · Yong Zhao🇺🇸
Recently, a novel approach has been proposed to compute parton distributions through the use of boosted correlators fixed in the Coulomb gauge from lattice QCD, within the framework of Large-Momentum Effective Theory (LaMET). This approach circumvents the need for Wilson lines, potentially enhancing the efficiency and accuracy of lattice calculations. In this work, we present the first exploratory implementation of the Coulomb gauge method for calculating nucleon unpolarized, helicity, and transversity parton distribution functions (PDFs). The calculations are performed on a Highly-Improved-Staggered-Quark ensemble with lattice spacing $a = 0.06$ fm, volume $L_{s}^{3} \times L_{t} = 4 8^{3} \times 64$ , and valence pion mass $m_{π} = 300$ MeV, employing boosted nucleon states with momenta up to 3.04 GeV. Our lattice predictions for the valence-quark PDFs -- extracted from the real part of the correlators -- show good convergence with increasing nucleon momentum and are compatible with the most recent global analyses for all spin structures. On the other hand, the full-quark-channel PDFs obtained from the imaginary part of the correlators exhibit discrepancies between the two large nucleon momenta considered, although the results at the higher momentum are consistent with phenomenology. The discrepancies are likely driven by stronger excited-state contamination in the imaginary matrix elements, which is consistent with the observation in the literature. Overall, this work demonstrates the efficacy of the Coulomb gauge approach for nucleon PDFs and serves as a benchmark for its broader applications.
Comments:
36 pages, 19 figures
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2602.11283 [pdf]
8 citations
10
[Submitted on 12 Feb 2026] (cross-list from hep-ph)
A study of charged-particle multiplicity distribution in high energy p-O collisions
Yuri N. Lima🇧🇷 · Lucas J. F. Silva🇧🇷 · Andre V. Giannini🇵🇹 · Marcelo G. Munhoz🇧🇷
This study investigates the multiplicity distribution of charged particles generated in $p$ -O collisions, employing Pythia (Angantyr) and $k_{T}$ -factorization approach. Oxygen nucleus configurations are sampled using a $α$ -cluster model to evaluate both formalisms and assess how initial nucleus configuration influences the properties of the produced final states. Results obtained through clustering are systematically compared to those derived from the Woods-Saxon nuclear distribution. The analysis encompasses various pseudorapidity intervals ( $∣ η ∣ <$ 0.5, 1.0, 2.0, 3.0) and center-of-mass energies ( $s =$ 2.36, 5.02, 7.0, 13.0 TeV). Based on the resulting distributions, we examine the KNO scaling effect and fit the distributions with the double NBD model for parameterization, aiming to accurately characterize the observed results and elucidate contributions from both soft and semi-hard processes. Our results indicate that different geometric descriptions of the oxygen nucleus project significantly different multiplicities of charged particles, especially for large multiplicities and higher pseudorapidity. We also observed that multiplicity of charged particles calculated with Pythia reveals significantly different behavior from that calculated with $k_{T}$ -factorization.
Comments:
v1: 12 pages, 7 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2602.11452 [pdf]
0 citations
11
[Submitted on 12 Feb 2026] (cross-list from hep-ph)
QCD matter at a finite magnetic field and nonzero chemical potential
Zhi-Ying Qin🇨🇳 · Bo Feng🇨🇳 · Ya-Hui Hou🇨🇳 · Hong-Yue Song🇨🇳 · Wen-Chao Zhang🇨🇳 · Hua Zheng🇨🇳 · Shi-Jun Mao🇨🇳
We construct a hybrid equation of state (EoS) by smoothly interpolating the EoS in the hadron resonance gas at low temperatures to that in the ideal parton gas at high temperatures, and employ it to study the properties of the quantum chromodynamics (QCD) matter under finite magnetic field and nonzero chemical potential. In this work, we neglect the anomalous magnetic moment effects of both charged and neutral particles. Our results show that the thermodynamic observables such as the entropy density, the pressure, the energy density, the trace anomaly, and the specific heat at constant volume are sensitive to both finite magnetic field and chemical potential. As the chemical potential increases from zero, these quantities rise in both the hadronic and quark-gluon plasma phases. In contrast, introducing a magnetic field suppresses them at low temperatures but enhances them at high temperatures. Furthermore, nonzero chemical potential and magnetic field introduce nontrivial modifications to the squared speed of sound. Both effects increase its value near the critical temperature while reducing it at lower temperatures. When both the chemical potential and the magnetic field are present, their influences superimpose, leading to more intricate changes in the thermodynamic behavior. Finally, we compare our results with the lattice QCD data for the quadratic fluctuations of conserved charges and their correlations. The model successfully reproduces the temperature dependence of these observables at $e B = 0$ and 0.04 GeV $^{2}$ . However, at the stronger field strength $e B = 0.14$ GeV $^{2}$ , the model underestimates the magnitudes while still capturing the overall temperature trend.
Comments:
18 pages, 3 figures. Revised according to the referee's comments
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2602.11713 [pdf]
PRD(2026)·2 citations
12
[Submitted on 12 Feb 2026] (cross-list from hep-ph)
QCD phase diagram in a magnetic field with baryon and isospin chemical potentials
Yu Hamada🇩🇪 · Muneto Nitta🇯🇵 · Zebin Qiu🇯🇵
Based on the chiral perturbation theory at the leading order, we present the phase diagram of low-energy QCD in a magnetic field at finite baryon and isospin chemical potentials. The phase diagram consists of the QCD vacuum, the chiral soliton lattice, the uniform charged pion condensation, an Abrikosov vortex lattice of the charged pions, a baryonic vortex lattice composed of neutral and charged pion vortices with their topological linking number being the baryon number, and a hybrid phase of chiral soliton and vortex lattices, with their intersections carrying the baryon number. While the chiral soliton lattice demands ultra-strong magnetic field $\sim 1 0^{19}$ G,the intersection phase appears at $\sim 1 0^{17}$ G, which is more realistic in neutron stars.
Comments:
9 pages, 4 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Superconductivity (cond-mat.supr-con); Nuclear Theory (nucl-th)
arXiv:
2602.11762 [pdf]
6 citations
13
[Submitted on 12 Feb 2026] (cross-list from nucl-ex)
Elliptic flow of strange and multi-strange hadrons in isobar collisions at $s_{NN} = 200 GeV$ at RHIC
The STAR Collaboration
We report a systematic measurement of elliptic flow ( $v_{2}$ ) of $K_{s}^{0}$ , $Λ$ , $Λ$ , $ϕ$ , $Ξ^{-}$ , $Ξ^{+}$ , and $Ω^{-}$ + $Ω^{+}$ at mid-rapidity ( $∣ y ∣ < 1.0$ ) for isobar, $_{44}^{96}$ Ru+ $_{44}^{96}$ Ru and $_{40}^{96}$ Zr+ $_{40}^{96}$ Zr, collisions at $s_{NN}$ = 200 GeV. The transverse momentum ( $p_{T}$ ) dependence of $v_{2}$ is studied for various centrality classes. The number of constituent quark scaling of (multi-)strange hadrons is found to hold approximately within 20%, suggesting the development of partonic collectivity in isobar collisions similar to that observed in Au+Au collisions at $s_{NN}$ = 200 GeV. The average $v_{2}$ ratio shows $\sim$ 2% deviation from unity in central and mid-central collisions for strange hadrons, indicating a difference in nuclear structure and deformation between the isobars. The $v_{2}$ in isobaric collisions is compared to Cu+Cu, Au+Au, and U+U collisions at similar collision energies. We observe an increase in $v_{2} (p_{T})$ with increasing system size. The difference in $v_{2}$ between the isobar and other collision systems increases with $p_{T}$ . The results are compared with a multi-phase transport model calculations with a deformed density profile to provide further insight into the nuclear structure of these isobars.
Comments:
13 pages, 14 figures
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2602.12094 [pdf]
1 citation
14
[Submitted on 12 Feb 2026] (cross-list from hep-ph)
Studies of low energy $l + p \to l + p + γ$ process in covariant chiral perturbation theory
Xu Wang🇨🇳 · Kai-Ge Kang🇨🇳 · Zhiguang Xiao🇨🇳 · Han-Qing Zheng🇨🇳
This study presents a tree-level calculation of the scattering amplitude for the $l p \to l p γ$ (with a hard photon) process within the framework of Chiral Perturbation Theory. Our calculations, based on the $O (p^{2})$ and $O (p^{3})$ nucleon-pion Lagrangians, aim to provide a theoretical prediction for the differential cross-section. The result shows that explicit inclusion of the nonzero lepton mass significantly influences the low energy differential cross section for $μ p \to μ p γ$ process. The kinematic region of the present experimental data is beyond the validity domain of the $χ$ PT and is therefore not suitable for determining the low-energy constants (LECs). By comparing our results with future experimental data, we expect to determine the values of the LECs as a further test of $χ$ PT as an effective low-energy theory of QCD. The process is of significant interest as it can help to determine the generalized polarizabilities of the nucleon.
Comments:
15 pages, 9 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2602.12119 [pdf]
0 citations
15
[Submitted on 12 Feb 2026] (cross-list from hep-ph)
Resonating group method for baryon-baryon interactions with unequal oscillator frequencies and its application to the $N Δ$ system in a chiral quark model
Ke-Rang Song🇨🇳 · Fei Huang🇨🇳
The resonating group method (RGM) is widely used to investigate baryon-baryon interactions at the quark level, typically under the assumption that the two baryons involved share an identical harmonic-oscillator frequency. In reality, however, when a specific interaction Hamiltonian is given, different baryons should have unequal oscillator frequencies due to distinct interaction potentials induced by their different quantum numbers. In this work, we develop a new quark-level RGM formalism for baryon-baryon systems with unequal oscillator frequencies, with the aim of providing a unified and consistent framework for describing both single-baryon properties and baryon-baryon interactions. We present the formalism for solving bound-state and scattering problems, with particular emphasis on constructing the wave functions of two-baryon systems with unequal oscillator frequencies. The proposed formalism is then applied to the $N Δ$ system within a chiral SU(3) quark model, where the quark-quark interaction includes, in addition to the one-gluon exchange (OGE) and a phenomenological confinement potential, the nonet scalar and pseudoscalar meson exchanges arising from the spontaneous breaking of chiral SU(3) symmetry. The distinctive features of the newly developed formalism are demonstrated by comparing the results from the new formulation with those from traditional calculations.
Comments:
17 pages, 12 figures. Updated version accepted for publication in Phys. Rev. D
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2602.12148 [pdf]
0 citations
16
[Submitted on 12 Feb 2026] (cross-list from cond-mat.quant-gas)
Second excited state of $^{4} He$ tetramer
A. Deltuva🇱🇹
The four-boson universality suggests the existence of the second excited tetramer state in a system of cold $^{4} He$ atoms. It is not bound but could be seen as a resonance in the atom-trimer scattering. This process is rigorously calculated using the momentum-space transition operator framework with two realistic interatomic potentials. The $S$ -wave phase shift and cross section show a resonant behavior below the excited trimer threshold, but there are sizable nonresonant contributions from $P$ and $D$ waves as well. The position and width of the resonant state is determined, and for the latter significant finite-range effects are found.
Comments:
3 figs
Subjects:
Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th); Atomic Physics (physics.atom-ph)
arXiv:
2602.12225 [pdf]
PRA(2026)·0 citations
17
[Submitted on 12 Feb 2026] (cross-list from hep-ph)
Systematic Operator Construction for Non-relativistic Effective Field Theories: Hilbert Series versus Young Tensor
Yong-Kang Li🇨🇳 · Yi-Ning Wang🇨🇳 · Jiang-Hao Yu🇨🇳
This work establishes a systematic framework for operator construction in the non-relativistic effective field theory, incorporating both the three dimensional Euclidean symmetry and the internal symmetries. By employing double cover of the rotation group, we extend the Hilbert series to the non-relativistic systems, and eliminates redundancies introduced by the spin operator. We also generalize the Young tensor method to the non-relativistic cases through the $S U (2)$ semi-standard Young tableaux, which allows for the construction of operator bases with repeated fields at any given mass dimension. Utilizing the Young tensor technique and Hibert series as cross-check, we obtain the complete operator bases for the following cases: heavy particle (and also heavy quark) effective theory operators up to mass dimension 9; pion-less effective theory operators, including nucleon-nucleon contact interactions up to $O (Q^{4})$ and three-nucleon interactions at $O (Q^{2})$ ; and finally the spin-1/2 dark matter-nucleon operators up to $O (v^{4})$ .
Comments:
96 pages, 24 tables, 4 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2602.12263 [pdf]
1 citation

Affiliations

first authorsco-authorsvia INSPIRE