Nuclear Theory·nucl-th

Wednesday·May 20, 2026

9 papers—4 primary·5 cross-listed

01
Coulomb Corrections to Three-Nucleon Moments
Ha S. Nguyen🇺🇸 · Jared Vanasse🇺🇸
The Helium-3 ( $^{3} He$ ) magnetic moment and Gamow-Teller (GT) matrix element in triton ( $^{3} H$ ) $β$ -decay are calculated in pionless effective field theory ( $EFT (/ π)$ ) to next-to-leading order (NLO). Coulomb corrections are included perturbatively to $O (α)$ in this framework and should naively be $α M_{n} / p^{*} \sim 8%$ corrections, where $p^{*} \sim 88.5$ MeV is related to the three-nucleon binding momentum. Fitting the two-nucleon iso-vector magnetic current low-energy constant (LEC), $L_{1}$ , to the $^{3} H$ magnetic moment and the two-nucleon iso-scalar magnetic current LEC, $L_{2}$ , to the deuteron magnetic moment we find the NLO $^{3} He$ magnetic moment in units of nuclear magnetons is -2.130 and the surprisingly small $O (α)$ correction is 0.00335, $\approx 0.18%$ of the LO $EFT (/ π)$ prediction. The leading-order (LO) GT matrix element for $^{3} H$ $β$ -decay is 0.9806 while again it has a surprisingly small $O (α)$ Coulomb correction of $- 0.000740$ , $\approx 0.08%$ of the LO $EFT (/ π)$ prediction. At NLO we calculate the GT matrix element of $^{3} H$ $β$ -decay, including the $O (α)$ Coulomb correction, in terms of the two-nucleon axial current LEC $l_{1, A}$ . Fitting $l_{1, A}$ to the $^{3} H$ half-life we make a prediction for the proton-proton fusion reduced matrix element of $Λ (0) = 2.776 (331)$ . Finally, we attempt to explain the unusually small size of the $O (α)$ corrections by investigating the Wigner-SU(4) expansion of these observables.
nucl-th0 citations
02
Ab initio correlations between neutrinoless and two-neutrino double-beta decays in $^{48}$ 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 $2 ν β β$ and $0 ν β β$ decays of $^{48}$ Ca. This framework reproduces the locations of several main resonance peaks in the Gamow-Teller (GT) strength distribution for the $^{48} Ca \to^{48} Sc$ transition. The cumulative GT strength indicates missing contributions from two-body weak currents, corresponding to an effective quenching factor of $q ≃ 0.84$ . Incorporating this quenching yields a $2 ν β β$ nuclear matrix element (NME) in excellent agreement with experiment. Applying the same framework to $0 ν β β$ decay, and including the contribution from short-range operators, we obtain a total NME of $M^{0 ν} = 1.00 - 2.02$ . Using 34 non-implausible chiral Hamiltonians, we establish from first principles strong linear correlations between the $0 ν β β$ NME and the NMEs governing $2 ν β β$ decay and double GT transitions. Combining these correlation relations within the 95% confidence level with the experimental $2 ν β β$ -decay data yields a constrained prediction of $M^{0 ν} = 1.30 - 1.65$ . This work establishes IM-NCCI as a complementary ab initio framework for nuclear weak decays and opens a pathway toward constraining $0 ν β β$ NMEs in heavier candidate nuclei using experimentally accessible $2 ν β β$ -decay data.
nucl-thhep-phnucl-ex4 citations
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 $^{3}$ He $(p, e^{+} ν_{e})$ $^{4}$ He (''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 $S (0) = (8.7 \pm 0.9) \times 1 0^{- 20}$ 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 $^{3}$ He $(n, γ)$ $^{4}$ He (''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
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 $40 < A < 90$ and their soft electric dipole ( $E 1$ ) excitations based on the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc). Three candidates, $^{43}$ Si, $^{69}$ Ti, and $^{75}$ Cr, are selected for detailed analysis. Unique features are identified in the decoupled densities of possible $s$ - and $p$ -wave deformed halo nuclei in this mass region, which are influenced by large high- $l$ 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 $40 < A < 90$ 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
05
Looking at the Entropy in a Proton through a QGP Lens
Dmitri E. Kharzeev🇺🇸 · Krishna Rajagopal🇺🇸
We investigate the interplay between the thermodynamic (Gibbs) entropy of quark-gluon plasma (QGP) and the quantum entanglement entropy characteristic of confined hadronic states across the quark-hadron phase transition. In the deconfined regime, entropy is well described by the statistical mechanics of colored quarks and gluons. Upon hadronization, however, the macroscopic Gibbs entropy of the plasma cannot simply vanish; instead, it is reorganized into the configurational entropy of a gas of colorless hadrons together with quantum correlations among the confined partons within each hadron. We show that the entanglement entropy of the internal partonic wave functions inside hadrons provides a natural repository for this ``converted'' thermodynamic entropy, reconciling the apparent reduction of macroscopic entropy with the second law of thermodynamics. Either by extrapolating from known facts about deep inelastic scattering, or starting from model descriptions of the proton wave function, or starting from the Hagedorn spectrum of its resonances, we provide three estimates of the magnitude of the entanglement entropy carried by a proton, with very different uncertainties. All three estimates indicate that the internal entanglement entropy of the proton is similar in magnitude to the Gibbs entropy of the QGP droplet from which the proton formed as QGP cools through the quark-hadron transition, as for example throughout the universe microseconds after the Big Bang. These results suggest that entanglement entropy offers a bridge between the quantum information content of hadronic states and the thermodynamic entropy of the quark-gluon plasma, providing a new lens on the microscopic mechanism of confinement and the nature of the QCD phase transition.
↳ hep-phnucl-th3 citations
06
The stability of color-flavor-locked quark matter and massive CFL quark stars
Wen-Li Yuan🇨🇳 · Bikai Gao🇯🇵
Owing to the emergence of attractive interactions between quarks, color superconductivity is expected to occur, with the color-flavor-locked (CFL) phase favored at high densities. This work investigates the absolute stability of beta-equilibrated CFL quark matter in bulk within the modified Nambu-Jona-Lasinio model, under color and electric charge neutrality conditions relevant to compact stars. Motivated by the possible existence of an ultra-low-mass central compact object in the supernova remnant HESS J1731-347 and the "mass-gap" secondary component in the GW190814 event, we systematically explore how vector repulsion, attractive diquark pairing, and nonperturbative vacuum effects influence the stiffness of CFL quark matter and its stability. Our findings suggest the existence of a physically viable region of parameter space in which the CFL phase is the true ground state of strongly interacting matter, thereby theoretically supporting the scenario of self-bound quark stars. This configuration is not only consistent with current astrophysical constraints from NICER and LIGO/Virgo observations, but also provides a possible explanation for both the $2.6 M_{⊙}$ secondary component in GW190814 and the ultra-low-mass compact object with $M = 0.7 7_{- 0.17}^{+ 0.20} M_{⊙}$ in HESS J1731-347.
↳ hep-phastro-ph.HEnucl-th2 citations
07
Magnetized neutron stars: perturbative versus fully-numerical approaches
Debarati Chatterjee🇮🇳 · Daw Guttmann🇫🇷 · Jérôme Novak🇫🇷 · Micaela Oertel🇫🇷 · Martin Jakob Steil🇩🇪
(1) Background: for the study of highly magnetized neutron stars observed as magnetars, and to quantify the effect of this intense magnetic field onto the star's structure and shape which can be particularly relevant for the study of emission of continuous gravitational waves, both numerical and perturbative approaches have been developed. (2) Methods: we compare these two approaches in General Relativity with the limitation to the case where the magnetic field has a purely poloidal structure. The perturbative one (Konno-99) assumes that the deformation induced by the magnetic field is small and that this field arises only from dipole currents. The full numerical one is based on the library LORENE. (3) Results: we have used both approaches to compute the magnetic field distribution and the deformation of the star, varying the value of the magnetic field at the pole, the compactness of the star and its equation of state. (4) Conclusions: whereas the perturbative approach breaks down for very high polar magnetic field values (typically above a few times $1 0^{16}$ G), it gives very good results for observed values, even in magnetars. On the contrary, the numerical code exhibits resolution problems for relatively low magnetic field values (typically $1 0^{10}$ G), which translates into imprecise computation of the star's deformation and mass quadrupole moment.
↳ astro-ph.HEgr-qcnucl-th0 citations
08
Lindblad-driven quarkonium production in heavy-ion collisions
Néstor Armesto🇪🇸 · Miguel Ángel Escobedo🇪🇸 · Elena G. Ferreiro🇪🇸 · Víctor López-Pardo🇪🇸
We study the production of the conventional quarkonium states in ultrarelativistic heavy-ion collisions using an open quantum system framework based on the Lindblad equation. Starting from the complex-valued in-medium potential, we derive the dissociation temperature and thermal decay width for each state, and compute their survival probabilities for a system undergoing Bjorken expansion. We then extend the framework to include recombination from thermalized charm and bottom quarks in the quark-gluon plasma, deriving a coalescence model for quarkonia from the Lindblad equation under the adiabatic approximation. The methodology provides a unified, first-principles-inspired description of suppression and recombination for both charmonium and bottomonium.
↳ hep-phhep-exnucl-exnucl-th4 citations
09
Charmonium properties at high temperatures from lattice QCD
Rasmus Normann Larsen🇩🇪 · Peter Petreczky🇺🇸 · Jorge Luis Dasilva Golan🇺🇸 · Johannes H. Weber🇩🇪
We study charmonium properties at non-zero temperature in the temperature range 153 MeV $< T <$ 305 MeV using lattice QCD. We use HISQ action for dynamical quarks and Wilson clover action for valence charm quarks and calculate the correlation function of extended meson operators. Our lattice QCD results are consistent with the existence of all charmonium states below the open charm threshold in this temperature region. However, charmonium states acquire sizable thermal width, which increases with increasing temperature. The size of the thermal width follows the hierarchy of charmonium sizes, i.e. the smaller ground state charmonium has a smaller thermal width than the larger excited charmonia.
↳ hep-lathep-phnucl-th1 citation

Affiliations

first authorsco-authorsvia INSPIRE