Nuclear Theory·nucl-th

Thursday·June 25, 2026

8 papers—4 primary·4 cross-listed

01
Ab initio calculations of parity-violating electron scattering off $^{48}$ Ca and $^{208}$ Pb
Frederic Noël🇨🇭 · Matthias Heinz🇺🇸 · Martin Hoferichter🇨🇭 · Takayuki Miyagi🇯🇵 · Achim Schwenk🇩🇪
Parity-violating electron scattering off nuclei both serves as a low-energy precision probe to test electroweak interactions and allows one to access neutron distributions inside nuclei. It has implications for strong interactions in dense neutron-rich environments, also providing constraints for the properties of matter in neutron stars. Precision measurements are available for $^{48}$ Ca and $^{208}$ Pb by the CREX and PREX collaborations, respectively, and their interpretation requires advanced nuclear-structure calculations to draw firm conclusions. We perform the first ab initio calculations of the parity-violating asymmetry $A_{PV}$ based on nuclear forces from chiral effective field theory, fully including corrections due to Coulomb distortion effects. Based on these results, we critically reexamine correlation analyses employed to infer weak radii and quantify the resulting tensions between ab initio and experimental results. We find that ab initio calculations prefer values of $A_{PV}$ slightly smaller and larger than observed for $^{48}$ Ca and $^{208}$ Pb, respectively, with a global significance of $1.9 σ$ . Using theoretically consistent inputs for charge and weak densities, we infer from the experimental $A_{PV}$ a neutron skin of $^{208}$ Pb of $R_{n} - R_{p} = 0.187 (25) (18)$ fm, substantially smaller than that reported by PREX II.
nucl-thastro-ph.HEhep-exhep-ph+12 citations
02
Two-Body Scattering Observables from Finite-Volume Real-Time Evolution
Lucas Platter🇺🇸
We study two-body scattering observables from real-time evolution in a finite periodic box. The system consists of two distinguishable particles on a two-dimensional lattice interacting through pointlike $s$ - and $p$ -wave interactions. We evolve their wave packets in real time, define detector observables through angular wedges in the relative coordinate, and attach infinite-volume labels obtained from the bound-state pole equation and the low-energy scattering amplitude. We train a convolutional neural network on this data and test its performance on held-out scattering problems and find that is able to predict the total magnitude and angular shape for previously unseen Hamiltonians.
nucl-th0 citations
03
The renormalization of the shell-model neutrinoless double-beta decay operator starting from effective field theory (I)
L. Coraggio🇮🇹 · G. De Gregorio🇮🇹 · S. L. Lyu🇮🇹 · N. Itaco🇮🇹
In this work, we approach for the first time the task to perform a shell-model calculation of the matrix element for the neutrinoless double-beta decay, within a fully-consistent framework where the expressions of the nuclear Hamiltonian and of the decay operators have been derived through chiral perturbation theory. More precisely, the effective shell-model Hamiltonian and all transition operators have been constructed by way of the many-body perturbation theory, and then employed to calculate both spectroscopic properties of the nuclei involved in the decays under our consideration - namely 48Ca, 76Ge, and 82Se -, as well as the nuclear matrix elements of the electromagnetic and neutrinoless double-beta decays. We also present a study of the convergence properties of the calculated matrix elements in order to provide the elements for an estimate of the theoretical uncertainty.
nucl-thhep-exnucl-ex0 citations
04
$K^{-}$ -Driven Direct Urca Cooling in Rotating Neutron Stars: A Bayesian Study
Aprajita Shrivastava🇮🇳 · Debanjan Guha Roy🇮🇳 · Sarmistha Banik🇮🇳
We investigate the onset of antikaon ( $K^{-}$ ) condensation and its implications for the equation of state (EoS) and cooling of neutron stars (NSs) within density-dependent relativistic mean-field parametrisations DD2 and MPE. Treating the antikaon - nucleon optical potential ( $U_{K}$ ) as a free parameter in the range $[- 180, - 60]$ MeV, we constrain it using Bayesian inference with NICER mass-radius observations of PSR J0030+0451 and PSR J0740+6620. The inferred posterior distributions favour strongly attractive in-medium $K^{-}$ interactions, while their broad widths indicate only weak constraints on $U_{K}$ by astrophysical observations. More attractive values of $U_{K}$ lead to an earlier onset of $K^{-}$ condensation, enhanced softening of the EoS, and lower Direct Urca (DU) threshold densities. The condensation threshold is systematically lower in DD2 than in MPE, while finite entropy further promotes the onset of rapid cooling. The $K^{-}$ -induced enhancement of the proton fraction ( $y_{p}$ ) substantially affects a larger volume of the stellar core, i.e. capable of sustaining rapid DU cooling. We further show that rapid rotation suppresses DU cooling by reducing the central density and $y_{p}$ , thereby shrinking the DU-active core. This suppression is more pronounced for MPE than for DD2. Our results demonstrate that $K^{-}$ condensation, finite entropy, and rotation jointly exert a strong influence on the conditions for rapid neutrino cooling in NSs.
nucl-thastro-ph.HE1 citation
05
Low lying excitations in $^{150}$ Pm
A. Pal · S. Basak · T. Bhattacharjee · Nazira Nazir · G. H. Bhat · S. Jehangir · D. Kumar · A. Saha · S. S. Alam · D. Banerjee · A. Das · A. Adhikari and 10 other authors
The low lying excitations in odd-odd $^{150}$ Pm have been studied through proton induced reaction with an array of five Compton suppressed Clover HPGe and one segmented planar Ge detectors. The relative excitation functions for the observed $γ$ rays have been studied using singles data at two beam energies of 8~MeV and 9~MeV. 16 new $γ$ rays and 15 new levels have been placed in the level scheme of $^{150}$ Pm based on $γ - γ$ coincidence data. The relative intensities for the observed $γ$ rays have been determined using total and gated projections. Tentative spin-parity assignments were made to few low lying excitations of $^{150}$ Pm, using limited angular distribution data and other information. Lifetimes were estimated for two excited levels in this nucleus using using generalized centroid difference analysis, applied in the nanosecond range, with Ge detectors. Large basis shell model and projected shell model calculation were performed to interpret the experimentally observed levels. The present work indicates 1 $^{-}$ ground state, a 2 $^{-}$ state close to the ground state ( $\sim$ 50~keV) and a low lying 6 $^{-}$ isomeric state in this odd-odd nucleus along with emerging band structures developed with two quasiparticle configurations.
↳ nucl-exnucl-th0 citations
06
Amortized Simulation-Based Inference of Relativistic Mean-Field Couplings for Neutron-Star Equations of State
Prashant Thakur🇰🇷 · Tuhin Malik🇵🇹
We present a simulation-based inference framework for constraining microscopic relativistic mean-field parameters of neutron-star equations of state. Neural posterior estimation is applied to two representative RMF families, a density-dependent DDB model and a nonlinear RMF-NL model, using nuclear saturation properties, chiral effective-field-theory pure-neutron-matter pressures, and the maximum-mass constraint as conditioning observables. The inferred posteriors are validated against the conventional nested sampler (PyMultiNest) calculations and tested with the TARP coverage diagnostic. For both RMF parametrizations, the neural posterior reproduces the nested-sampling constraints on model couplings, nuclear-matter properties, and neutron-star observables with no significant bias. The amortized estimator generates $3 \times 1 0^{4}$ posterior samples in about $2.5 s$ on a CPU, enabling a rapid inference workflow without the need for retraining for updated data. This constitutes a proof of concept that NPE-emulated RMF models, once validated, can be safely used for superfast exploratory inference. As an additional mock-observation test, imposing $R_{1.4} = 12 km$ and $M_{max} > 1.97 M_{⊙}$ leads to consistent predictions for the maximum-mass configuration, with DDB giving $M_{max} = 2.1 0_{- 0.07}^{+ 0.09} M_{⊙}$ , $R_{max} = 10.7 1_{- 0.21}^{+ 0.14} km$ and RMF-NL giving $M_{max} = 2.0 5_{- 0.06}^{+ 0.10} M_{⊙}$ , $R_{max} = 10.6 9_{- 0.19}^{+ 0.18} km$ ; although fixing $R_{1.4}$ confines both families to a narrow EOS region, RMF-NL remains marginally softer than DDB at high density, consistent with its slightly lower maximum mass.
↳ astro-ph.HEnucl-th0 citations
07
In-medium QCD splittings beyond the soft, large- $N_{c}$ and harmonic-oscillator approximations all at once
Marco Leitão🇫🇷 · José Guilherme Milhano🇵🇹 · Alba Soto-Ontoso🇪🇸
Nearly thirty years ago, Baier, Dokshitzer, Mueller, Peigné, Schiff, and Zakharov (BDMPS-Z) introduced a formalism to calculate the fully differential probability for a high-energy quark or gluon to radiate inside a finite-volume QCD plasma. We report on the first, complete numerical solution to the BDMPS-Z equations for in-medium QCD splittings. Our numerical routines are precise across phase-space, enabling a determination of the in-medium splitting functions that is significantly beyond the state-of-the-art, including finite-energy effects, subleading-color contributions, and a realistic model for parton-medium interactions. We quantify the uncertainties associated with standard approximations in the literature, revealing substantial deviations across phase-space. This work opens a path toward more precise calculations of jet observables and for powerful new constraints of medium parameters from high-energy heavy-ion collider data.
↳ hep-phhep-exnucl-th2 citations
08
Positron-Emitting and Electron-Capturing Double-Beta Processes in the Standard Model and Beyond
Lukáš Gráf🇨🇿 · Jenni Kotila🇫🇮 · Oliver Scholer🇺🇸
We study positron-emitting and electron-capturing double-beta-decay modes as probes complementary to the usual double beta decay. Motivated by the proposed NuDoubt++ experiment, we analyze the candidate isotopes $^{78}$ Kr, $^{106}$ Cd, and $^{124}$ Xe, providing nuclear matrix elements and phase-space factors for both neutrinoful and neutrinoless modes. For the Standard-Model channels, we find that $2 ν$ ECEC and $2 ν β^{+}$ EC are the most experimentally accessible, whereas $2 ν β^{+} β^{+}$ remains strongly phase-space suppressed. For the neutrinoless channel, we interpret a projected sensitivity of $T_{1/2}^{0 ν} = 1 0^{24}$ y in terms of dimension-seven SMEFT operators and find sensitivity to lepton-number-violating new-physics scales of order 1-100 TeV. We further show that measurements in multiple isotopes can help to resolve degeneracies in multi-operator scenarios, making positron-emitting double-beta searches a useful complement to conventional neutrinoless double beta decay experiments.
↳ hep-phnucl-exnucl-th0 citations

Affiliations

first authorsco-authorsvia INSPIRE