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Nuclear Theory·nucl-th

Thursday·January 25, 2024

9 papers—4 primary·5 cross-listed

All9Primary4Cross-lists5
  1. 01

    Revisiting the helium isotope-shift puzzle with improved uncertainties from nuclear structure corrections

    Simone Salvatore Li Muli · Thomas R. Richardson · Sonia Bacca

    Measurements of the difference between the squared charge radii of the helion (He nucleus) and the -particle (He nucleus) have been characterized by longstanding tensions, recently spotlighted in the 3.6 discrepancy of the extractions from ordinary atoms versus those from muonic atoms. Here, we present a novel analysis of uncertainties in nuclear structure corrections that must be supplied by theory to enable the extraction of the difference in radii from spectroscopic experiments. We use modern Bayesian inference techniques to quantify uncertainties stemming from the truncation of the chiral effective field theory expansion of the nuclear force for both muonic and ordinary atoms. With the new nuclear structure input, the helium isotope-shift puzzle cannot be explained, rather it is reinforced to a 4 discrepancy.

    nucl-thphysics.atom-phPRL(2025)·13 citations
  2. 02

    Neutron star matter as a dilute solution of protons in neutrons

    J. Keller · K. Hebeler · C. J. Pethick · A. Schwenk

    Neutron stars contain neutron-rich matter with around 5% protons at nuclear saturation density. In this Letter, we consider equilibrium between bulk phases of matter based on asymmetric nuclear matter calculations using chiral effective field theory interactions rather than, as has been done in the past, by interpolation between the properties of symmetric nuclear matter and pure neutron matter. Neutron drip (coexistence of nuclear matter with pure neutrons) is well established, but from earlier work it is unclear whether proton drip (equilibrium between two phases, both of which contain protons and neutrons) is possible. We find that proton drip is a robust prediction of any physically reasonable equation of state, but that it occurs over a limited region of densities and proton fractions. An analytical model based on expanding the energy in powers of the proton density, rather than the neutron excess, is able to account for these features of the phase diagram.

    nucl-thastro-ph.HEnucl-exPRL(2024)·11 citations
  3. 03

    Effects of dilute neutron matter on the neutron star crust equation of state

    Guilherme Grams🇧🇪 · Jerome Margueron🇫🇷

    We develop a compressible liquid-drop model to describe the crust of neutron stars for which the role of the nuclear clusters, the neutron gas, and the electrons are clearly identified. The novelty relies on the contribution of the neutron gas, which is qualitatively adjusted to reproduce 'ab initio' predictions in dilute neutron matter. We relate the properties of dilute neutron matter to the ones of neutron stars crust and we compare the mean-field approximation to an improved approach that better describes dilute neutron matter. The latter is quite sensitive to the unitary limit, a universal feature of Fermi systems having a large value of the scattering length and a small interaction range. While the impact of the accurate description of dilute neutron matter is important in uniform matter (up to 30\% corrections with respect to a mean-field calculations), we find a reduction of this impact in the context of the crust of neutron stars due to the additional matter components (nuclear clusters and electrons). In agreement with our previous works, dilute neutron matter is however a necessary ingredient for accurate predictions of the properties of the crust of neutron stars.

    nucl-thastro-ph.HEEPJA(2024)·4 citations
  4. 04

    Relativistic meson-exchange currents in semi-inclusive lepton scattering

    Valerio Belocchi🇮🇹 · Maria Benedetta Barbaro🇮🇹 · Arturo De Pace🇮🇹 · Marco Martini🇫🇷

    We assess the impact of two-particle--two-hole excitations on the semi-inclusive electron scattering process (e,e'p) using a fully relativistic nuclear model calculation that precisely incorporates antisymmetrization. The calculation encompasses all contributions involving the exchange of a single pion and the excitation of a Delta resonance. Our results are compared with (e,e'p) data on carbon at kinematics where two-nucleon emission dominates. This work represents an essential step towards the microscopic computation of the two-particle--two-hole contribution to semi-inclusive neutrino reactions, crucial in the analysis of neutrino oscillation experiments.

    nucl-thhep-exhep-phPRC(2024)·9 citations

Affiliations

first authorsco-authorsvia INSPIRE