Nuclear Theory·nucl-th

Wednesday·April 1, 2026

14 papers—7 primary·7 cross-listed

01
Dimer Effective Field Theory
Cullen Gantenberg🇺🇸 · David B. Kaplan🇺🇸
While chiral perturbation theory for mesons is characterized by a momentum expansion in $Q / Λ_{χ}$ with $Λ_{χ} \sim 1$ GeV, existing formulations of effective theory for nucleon-nucleon scattering deviate from data at $Q \sim 300$ MeV or lower. We offer heuristic evidence that unsuspected nonanalytic structure exists in the complex momentum plane obstructing the effective field theory expansion in the spin-triplet channels, associated with the peak of the angular momentum barrier whose energy in low partial waves satisfies $k = M E \sim 300$ MeV. With this motivation, we construct a meromorphic function of $k^{2}$ we call the $C$ -matrix, for which the radius of convergence of its Taylor expansion in $k^{2}$ is equivalent to that of the momentum expansion of the effective field theory. Thus the range of validity of the effective theory is directly related to the pole structure of the $C$ -matrix. We uncover that pole structure and confirm that it is the source of the obstruction. The systematic inclusion of dimer fields as propagating degrees of freedom in the effective theory to account for those poles results in cut-off insensitive fits at order $Q^{0}$ to most of the lower partial wave phase shifts up to the pion production threshold, using only the one pion exchange part of the long-range nucleon-nucleon interaction. Our theory should be applicable to the singular potentials regularly found in atomic physics as well.
nucl-thphysics.atom-ph2 citations
02
Ab initio optical potentials for magnesium isotopes at intermediate energies: from stability to the island of inversion
G.H. Sargsyan · J. I. Fuentealba Bustamente · K. Beyer · Ch. Elster
We present the first calculations of ab initio nonlocal optical potentials for $^{24, 26, 28}$ Mg and $^{32}$ Mg isotopes using the leading-order term of the spectator expansion of multiple-scattering theory. We use the structure input from the ab initio symmetry-adapted no-core shell model (SA-NCSM), which provides translationally invariant, off-shell scalar and spin-projected densities so that structure and reaction inputs are treated on equal footing with no adjustable parameters. This leading-order potential reproduces $^{24}$ Mg neutron total, reaction, and elastic-scattering data at energies between 65 and 250 MeV and provides predictions for $^{26, 28}$ Mg and $^{32}$ Mg. We compare our prediction with those from uncertainty-quantified Koning-Delaroche (KDUQ) and Weppner-Penney global optical potentials, and with the ENDF nuclear data evaluations. These comparisons highlight some of the limitations of the global models, while also validating their use in reaction modeling near the N=20 island of inversion.
nucl-thnucl-exJ.Phys.G(2026)·0 citations
03
Multi-task deep neural network for predicting both nuclear fission yields and their experimental errors in peak-shaped data
Maomi Ueno · Enbo Zhang · Kazuma Fuchimoto · Satoshi Chiba · Jingde Chen · Chikako Ishizuka
The fission product yield (FPY) is crucially important information for numerous nuclear applications. However, the peak-shaped characteristics of FPY data present important challenges for predicting unobservable FPY data. To address these challenges, after applying Multi-task learning models to fission product yield data and their experimental error estimates, we introduce a novel loss function along with incorporation of the odd even effect. Our approach is intended to predict unknown fission yields and the associated experimental error. To demonstrate the effectiveness of our proposed method, we compared our proposed method with conventional methods that learn each dataset independently. Our findings demonstrate that the proposed methods can predict peak shaped data with experimental error estimates more effectively than earlier methods can.
nucl-th0 citations
04
Time evolution formalism in the complex scaling method: Application to the E1 response of $^{6}$ He
Yuma Kikuchi · Kiyoshi Katō · Takayuki Myo
Background: The complex scaling method (CSM) has been successfully used to describe many-body resonances as eigenvalues of the complex-scaled Hamiltonian in an appropriate $L^{2}$ basis representation. Its scope has subsequently been extended to many-body continuum states, strength functions, and scattering observables. However, a general framework that incorporates time evolution within the same CSM framework has not yet been established. Purpose: We formulate a time-evolution formalism as a natural extension of the CSM based on the extended completeness relation (ECR), and apply it to the electric dipole (E1) excitation of $^{6}$ He in order to clarify how an initially correlated three-body configuration evolves into continuum states. Methods: Time evolution is described by a complex-scaled time-evolution operator represented with the ECR. The formalism is first tested in a simple two-body model through comparison with a direct numerical solution of the time-dependent Schrödinger equation. It is then applied to the E1 excitation of $^{6}$ He in an $α + n + n$ three-body model, and the density distributions are analyzed in different Jacobi coordinate systems. Results: The present formalism reproduces the wave-packet evolution obtained in the direct time-dependent calculation. In the application to $^{6}$ He, the initial E1-excited state exhibits a correlated configuration and evolves into spatially extended continuum states. The time evolution of the density distributions indicates the coexistence of sequential decay through a core-neutron subsystem and direct breakup. Conclusions: The present formalism extends the scope of the CSM from spectral and scattering observables to real-time continuum dynamics, and provides a unified framework that connects initial-state correlations, continuum structure, and decay dynamics in weakly bound nuclei.
nucl-thPRC(2026)·0 citations
05
Nuclear shapes of Nb isotopes
Esperanza Maya-Barbecho · José-Enrique García-Ramos
The study of the structure of odd-mass nuclei in regions characterized by the interplay of multiple particle-hole configurations represents a major challenge in nuclear structure physics. The odd-mass niobium isotopes ( $Z = 41$ ), located near the $N = 60$ region, are of particular interest due to shape coexistence and quantum phase transitions. This work investigates the structure of the $^{93 - 103}$ Nb isotopes using the intrinsic-frame formalism of the interacting boson-fermion model with configuration mixing (IBFM-CM), aiming to determine nuclear shapes and explore shape coexistence, configuration crossing, and quantum phase transitions. We employ the intrinsic formalism of the IBFM-CM, including both 0p-0h (regular) and 2p-2h (intruder) configurations interacting with the unpaired nucleon, providing a self-consistent framework to study energy surfaces, shape coexistence, and intruder bands for both positive- and negative-parity states. A realistic Hamiltonian for niobium, determined in previous studies, is adopted. The formalism is applied to the $^{93 - 103}$ Nb isotopes for both positive- and negative-parity bands. A detailed analysis of the mean-field energy surfaces has been performed, including axial energy curves, triaxial energy surfaces in the $β - γ$ plane, and the corresponding equilibrium deformation parameters. The results reveal clear evidence of configuration coexistence and crossing along the isotopic chain. The existence of crossing configurations is demonstrated around $N = 60$ , corresponding to a quantum phase transition previously identified in the Sr and Zr isotopic chains. Furthermore, the presence of an unpaired nucleon in Nb influences the abruptness of the quantum phase transition, underscoring the sensitivity of the structural evolution to single-particle degrees of freedom.
nucl-thPRC(2026)·0 citations
06
Optimizing the description of the Delta region in the Ghent Hybrid model for single-pion production
M. Hooft🇧🇪 · A. Nikolakopoulos🇧🇪 · J. García-Marcos🇧🇪 · Y. De Backer🇧🇪 · T. Franco-Munoz🇧🇪 · K. Niewczas🇧🇪 · R. González-Jiménez🇪🇸 · N. Jachowicz🇧🇪
Single-pion production is an important contribution to the total neutrino-nucleus interaction cross section in accelerator-based neutrino oscillation experiments. The goal of this paper is to improve the Ghent model in the Delta resonance region by incorporating as many physical constraints as possible while keeping the number of fitted parameters as low as possible. A multipole decomposition of the model is performed allowing the use of $K$ -matrix theory to unitarize the background contributions. Watson's theorem is enforced by consistently modifying both the Delta and background contributions across all multipoles. Furthermore, the decay width and form factors of the Delta contribution are modified to ensure compliance with Watson's theorem, while the model is extended to include $ρ$ - and $ω$ -exchange diagrams. These adjustments are compared with other pion production models, as well as with CLAS pion electroproduction data on the nucleon. The results show considerable improvement in the description of the Delta peak region.
nucl-th1 citation
07
A systematic approach to Covariance matrix formulation in charged particle activation experiments
Tanmoy Bar
This work presents a detailed covariance and correlation matrix analysis for experimentally measured cross sections obtained using the activation technique. Both statistical and systematic contributions to the covariance matrix were explicitly calculated using sensitivity coefficients. The detector efficiency was determined by refitting standard source data with an exponential function, and the associated covariance matrix of the fitted parameters was propagated to estimate the uncertainty in efficiency at the relevant $γ$ -ray energy. The cross sections and the corresponding experimental parameters, such as beam flux, target thickness, $γ$ -ray intensity, and decay corrections, were taken from previously published measurements and are used here for the purpose of illustrating the covariance formalism. The resulting covariance and correlation matrices provide a comprehensive representation of uncertainties and their interdependencies. This formalism demonstrates the importance of including correlated uncertainties for reliable interpretation and comparison of experimental cross section data.
nucl-thnucl-exphysics.data-an0 citations
08
Quark-Mass Dependence of Light-Nuclei Masses from Lattice QCD and Trace-Anomaly Contributions to Nuclear Bindings
Debsubhra Chakraborty🇮🇳 · Noah Chavez🇺🇸 · Xiang Gao🇺🇸 · Nilmani Mathur🇮🇳 · Swagato Mukherjee🇺🇸
We present lattice QCD calculations of the masses of the deuteron, dineutron, Helium-3 and Helium-4 with physical sea quarks and valence quark masses corresponding to pion masses between 140 and 700 MeV. At the physical point, the lowest finite-volume two-nucleon energy levels exhibit the qualitative pattern of a bound deuteron and an unbound dineutron within uncertainties, while at heavier quark masses they indicate the presence of deeply bound states. Compared with expectations from low-energy effective field theories, the observed mass dependence of the binding energies provides first-principles constraints on the quark-mass dependence of two- and three-nucleon interactions. From the quark-mass variation of the nuclear energies, we determine nuclear sigma terms and quantify the response of light-nuclear masses to changes in the light-quark mass. Using the QCD trace anomaly relation, we decompose the nuclear binding energy into quark-mass and gluonic contributions around the deuteron mass scale of $μ = 2$ GeV. We find that the quark-mass contribution to the binding energy is small and approximately additive in nucleon number within current precision, whereas the gluonic component provides the dominant contribution and show milder increases with mass number.
↳ hep-lathep-phnucl-th1 citation
09
Determining the NJL Coupling and AMM in Magnetized QCD Matter via Machine Learning
Zigeng Ding🇺🇸 · Fan Lin🇺🇸 · Xinyang Wang🇺🇸
In this study, we investigate the phase structure of magnetized QCD matter by determining the field-dependent parameters of the Nambu-Jona-Lasinio (NJL) model through a physics-informed machine learning framework. Specifically, we focus on extracting the optimal functional forms for the running coupling constant $G (e B)$ and the quark anomalous magnetic moment (AMM) ratio $v_{2} (e B)$ , utilizing lattice QCD-computed quark condensate data as the ``ground truth". By embedding the NJL gap equation as a differentiable physics-constrained module, our neural network pipeline identifies continuous parameter functions that accurately reproduce the inverse magnetic catalysis (IMC) effect. Our results demonstrate that the magnetic field smoothly suppresses both $G$ and $v_{2}$ . This approach not only bridges the gap between effective models and lattice data but also provides new microscopic insights into the response of the QCD vacuum to strong magnetic fields.
↳ hep-phnucl-th1 citation
10
Comment on "Lattice QCD constraints on the critical point from an improved precision equation of state"
Roy A. Lacey (Department of Chemistry, Stony Brook University, Stony Brook, NY, USA)🇺🇸
A recent Letter~\cite{Borsanyi:2025dyp} employs lattice QCD calculations of the equation of state, combined with entropy-density contour analysis, to place a lower bound of $μ_{B} ≳ 450$ ~MeV on the location of the QCD critical endpoint (CEP). While the underlying lattice calculations represent an important advance in precision and systematic control, the method used to infer constraints on the CEP is not directly sensitive to critical behavior. In particular, the use of entropy contours does not directly probe the singular structure associated with the CEP, does not explicitly incorporate the relevant thermodynamic scaling fields, and relies on assumptions that are not strictly satisfied in finite systems. Consequently, the reported exclusion of a CEP below $μ_{B} \approx 450$ ~MeV cannot be regarded as model-independent, as model-independent constraints require observables that are directly sensitive to the singular scaling behavior associated with critical phenomena.
↳ hep-lathep-exhep-thnucl-ex+10 citations
11
Baryonic vortices in rotating nuclear matter
Kazuya Mameda🇯🇵 · Muneto Nitta🇯🇵 · Zebin Qiu🇯🇵
We investigate baryonic vortices as topological excitations in rotating nuclear matter within the framework of chiral perturbation theory. We identify two distinct configurations: local and global vortices, both carrying the baryon number as the topological charge associated with the third homotopy group $π_{3} (S^{3})$ . For the local vortex, similar to the vortex Skyrmion in a finite isospin chemical potential, charged pions form the condensate on the boundary and have a phase winding, while the neutral pion varies along the rotation axis inside the vortex core. On the other hand, a global vortex is formed by the condensate and phase winding of the neutral pion, while the charged pions vary on the inside along the rotation axis. Crucially, although global vortices are usually discarded in infinite systems due to logarithmic divergence in energy, we demonstrate that the finite-size constraint dictated by causality in a rotating frame regularizes the divergence physically, rendering the global vortex a viable excitation. We reveal an energetic competition between global and local vortex states, under the tunable parameters of rotation, system size, and baryon chemical potential. Our results suggest that the previously overlooked global vortex can play a significant role in the topological structure of rotating dense QCD matter.
↳ hep-phnucl-th3 citations
12
Imprint of the adjoint meson spectrum in the decay patterns of hidden-bottom tetraquarks
Sipaz Sharma🇩🇪 · Juan Andrés Urrea-Niño🇮🇪 · Nora Brambilla🇩🇪 · Francesco Knechtli🇩🇪 · Michael Peardon🇮🇪
We aim to clarify the experimentally observed near-degeneracy and decay patterns of the isospin, $I = 1$ , hidden-bottom tetraquarks $Z_{b} (10610)$ and $Z_{b} (10650)$ with quantum numbers $J^{P} = 1^{+}$ .We refer to them as $Z_{b}$ and $Z_{b}^{^{'}}$ , respectively. In particular, we find first evidence that the suppression of the decay of $Z_{b}^{^{'}}$ to $B B^{*} ˉ$ can be understood in the context of the Born-Oppenheimer Effective Field Theory (BOEFT). BOEFT enables writing both $Z_{b}$ and $Z_{b}^{^{'}}$ as superpositions of $Z_{1}$ and $Z_{2}$ tetraquark configurations. This decomposition naturally relates the decay patterns of $Z_{b}$ and $Z_{b}^{^{'}}$ to the degeneracy of the light degrees of freedom associated with $Z_{1}$ and $Z_{2}$ tetraquarks, {\it i.e.,} $1^{--}$ and $0^{-+}$ adjoint mesons, respectively. By calculating the adjoint meson correlators within the framework of lattice QCD, we get good indications that these adjoint mesons are degenerate.
↳ hep-lathep-exhep-phnucl-th0 citations
13
Revisiting QCD-induced little inflation with chiral density wave state and its implications on pulsar timing array gravitational-wave signals
Tae Hyun Jung🇰🇷 · Seyong Kim🇰🇷 · Jong-Wan Lee🇰🇷 · Chang Sub Shin🇰🇷 · Hee Beom Yang🇰🇷
We revisit QCD-induced little inflation in which the Universe begins with a large baryon chemical potential and undergoes a strong first-order QCD phase transition, generating an observable stochastic gravitational-wave background in the nano-Hz range relevant for pulsar timing array (PTA) observations. We point out that the conventional homogeneous transition from the quark-gluon plasma phase to the hadronic gas phase faces an unavoidable difficulty in achieving the required strength of supercooling for the observed baryon density. This motivates us to explore whether a qualitatively different phase structure at a large baryon chemical potential can alter the relation between the baryon density and the chemical potential, and thereby modify the supercooling history of the transition. Using the nucleon-meson model with isoscalar vector mesons, we determine the critical and spinodal structure of the chiral density wave (CDW) phase in the $(μ_{B}, T)$ plane. We find that the CDW phase exhibits a nontrivial structure and can remain metastable down to a low baryon density in a certain region of the parameter space. Taking into account the subsequent liquid-gas transition and phase separation, however, the released latent heat is too small to realize a viable QCD-induced little inflation scenario and its associated PTA-scale gravitational-wave signal. Our analysis sharpens the conditions under which QCD phase transitions may act as cosmological sources of nano-Hz gravitational waves, while clarifying the possible cosmological relevance of inhomogeneous QCD phases.
↳ hep-phastro-ph.COnucl-thPRD(2026)·0 citations
14
From Sub-eikonal DIS to Quark Distributions and their High-Energy Evolution
Giovanni Antonio Chirilli🇵🇱
Relating the high-energy dipole description of deep-inelastic scattering to the standard light-ray operator formulation at finite Bjorken $x_{B}$ is essential for connecting the small- $x$ framework to the usual partonic description. I demonstrate that this connection already emerges at the first sub-eikonal order. At the differential level, the first sub-eikonal correction is governed by a quark TMD-like light-ray operator. In the inclusive limit, after complete phase-space integration, it reconstructs the standard nonlocal quark and helicity distributions at nonzero $x_{B}$ . I then show independently that the same inclusive operator content follows from the high-energy limit of the leading-twist non-local operator product expansion, thereby establishing an explicit operator-level bridge between the shock-wave formalism and the non-local light-cone expansion. I further discuss the high-energy evolution of the corresponding operators at $x_{B} = 0$ . Rewriting the evolution equations in terms of dipole-type operator combinations, I identify an operator basis whose bilocal building blocks vanish in the zero-dipole-size limit, making the small-dipole behavior and the leading-logarithmic structure manifest. In the double-logarithmic approximation the evolution equations admit the usual mixed longitudinal-transverse Bessel-type solution when the transverse phase space is treated independently. When the transverse phase space is instead constrained by longitudinal ordering, the second logarithm is converted into a logarithm of energy, and in the symmetric double-logarithmic regime one recovers the fixed-coupling Kirschner-Lipatov exponent with the full finite- $N_{c}$ color factor $C_{F}$ .
↳ hep-phhep-thnucl-th4 citations

Affiliations

first authorsco-authorsvia INSPIRE