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Nuclear Theory·nucl-th

Wednesday·May 20, 2026

9 papers—4 primary·5 cross-listed

All9Primary4Cross-lists5
  1. 01

    Coulomb Corrections to Three-Nucleon Moments

    Ha S. Nguyen🇺🇸 · Jared Vanasse🇺🇸

    The Helium-3 () magnetic moment and Gamow-Teller (GT) matrix element in triton () -decay are calculated in pionless effective field theory () to next-to-leading order (NLO). Coulomb corrections are included perturbatively to in this framework and should naively be corrections, where MeV is related to the three-nucleon binding momentum. Fitting the two-nucleon iso-vector magnetic current low-energy constant (LEC), , to the magnetic moment and the two-nucleon iso-scalar magnetic current LEC, , to the deuteron magnetic moment we find the NLO magnetic moment in units of nuclear magnetons is -2.130 and the surprisingly small correction is 0.00335, of the LO prediction. The leading-order (LO) GT matrix element for -decay is 0.9806 while again it has a surprisingly small Coulomb correction of , of the LO prediction. At NLO we calculate the GT matrix element of -decay, including the Coulomb correction, in terms of the two-nucleon axial current LEC . Fitting to the half-life we make a prediction for the proton-proton fusion reduced matrix element of . Finally, we attempt to explain the unusually small size of the corrections by investigating the Wigner-SU(4) expansion of these observables.

    nucl-th0 citations
  2. 02

    Ab initio correlations between neutrinoless and two-neutrino double-beta decays in Ca

    X. Lian🇨🇳 · C. R. Ding🇨🇳 · C. L. Bai🇨🇳 · J. M. Yao🇨🇳

    We develop a novel ab initio in-medium no-core configuration-interaction (IM-NCCI) framework for nuclear charge-exchange processes by combining the in-medium similarity renormalization group with chiral nuclear Hamiltonians, and apply it to the and decays of Ca. This framework reproduces the locations of several main resonance peaks in the Gamow-Teller (GT) strength distribution for the transition. The cumulative GT strength indicates missing contributions from two-body weak currents, corresponding to an effective quenching factor of . Incorporating this quenching yields a nuclear matrix element (NME) in excellent agreement with experiment. Applying the same framework to decay, and including the contribution from short-range operators, we obtain a total NME of . Using 34 non-implausible chiral Hamiltonians, we establish from first principles strong linear correlations between the NME and the NMEs governing decay and double GT transitions. Combining these correlation relations within the 95% confidence level with the experimental -decay data yields a constrained prediction of . This work establishes IM-NCCI as a complementary ab initio framework for nuclear weak decays and opens a pathway toward constraining NMEs in heavier candidate nuclei using experimentally accessible -decay data.

    nucl-thhep-phnucl-ex4 citations
  3. 03

    A new analysis of the "hep" S-factor and the "hen" cross section

    Michele Viviani · Alex Gnech · Laura Elisa Marcucci · Alejandro Kievsky · Luca Girlanda

    We present a new accurate analysis of the HeHe (''hep'') reaction at astrophysical energies. The S-factor is computed using a state-of-the-art method to calculate the four-nucleon scattering and bound-state wave functions (the hyperspherical harmonic expansion), and by using nuclear interactions and accompanying electroweak nuclear currents obtained within the chiral effective field theory framework. Our analysis includes a detailed examination of the theoretical uncertainties coming from two different sources: the truncation of the interaction and current chiral expansions, and the model dependence. Our recommended final theoretical value for the hep S-factor at zero energyis keV b. We provide also the energy spectrum of the outgoing hep positrons which may be measured in future experiments. We include also an analysis of the ''sister'' reaction HeHe (''hen'') at low energies, showing that the calculation well reproduce the total cross section from thermal energies to few MeV, validating our results on the hep reaction.

    nucl-thastro-ph.SRhep-phnucl-ex0 citations
  4. 04

    Deformed neutron halo nuclei and soft dipole excitations in the 40<A<90 mass region

    Xiao Lu · Cong Pan · Hiroyuki Sagawa · Xiang-Xiang Sun · Shan-Gui Zhou

    We study deformed neutron halo nuclei in the mass region and their soft electric dipole () excitations based on the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc). Three candidates, Si, Ti, and Cr, are selected for detailed analysis. Unique features are identified in the decoupled densities of possible - and -wave deformed halo nuclei in this mass region, which are influenced by large high- configurations. It is shown that the dipole response is a highly sensitive observable to detect the halo component of the single-particle wave function in deformed halo nucleus, and it helps identify the configuration and the magnitude of deformation for halo nuclei in the mass region. Experimental confirmation of the dipole strength in the low-energy region is highly desirable to explore possible deformed halo candidates in the medium-heavy mass region.

    nucl-thPRC(2026)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE