Nuclear Theory

The precision of experimental data and analysis techniques is a key feature of any discovery attempt. A striking example is the proton radius puzzle where the accuracy of the spectroscopy of muonic atoms challenges traditional electron scattering measurements. The present work proposes a novel method for the determination of spatial moments from densities expressed in the momentum space. This method provides a direct access to even, odd, and more generally any real, negative and positive moment with order larger than −3 . As an illustration, the application of this method to the electric form factor of the proton is discussed in detail.

Measurements of angular correlations between initial and final particles in β decay remain one of the most promising ways of probing the Standard Model and looking for new physics. As experiments reach unprecedented precision well into the per-mille regime, proper extraction of results requires one to take into account a great number of nuclear structure and radiative corrections in a procedure which becomes dependent upon the experimental geometry. We provide here a compilation and update of theoretical results which describe all corrections in the same conceptual framework, point out pitfalls and review the influence of the experimental geometry. Finally, we summarize the potential for new physics reach.

In the present work, we use a finite range effective interaction to calculate the neutron skin thickness in 48 Ca and correlate these quantities with the parameters of nuclear symmetry energy. Available experimental data on the neutron skin thickness in 48 Ca are used to deduce information on the density slope parameter and the curvature symmetry parameter of the nuclear symmetry energy at saturation and at subsaturation densities. We obtained the constraints such as 54.5≤L( ρ 0 )≤97.5 MeV and 47.3≤L( ρ c )≤57.1 MeV for the density slope parameter. The constraints on the curvature symmetry energy parameter are obtained as −170.7≤ K sym ( ρ 0 )≤−43.4 MeV and −80.8≤ K sym ( ρ c )≤23.8 MeV. A linear relation between the neutron skin thickness in 48 Ca and in 2088 Pb is obtained.

We put a stringent constraint on the isovector nuclear interactions in the Skyrme-Hartree-Fock model from the centroid energy E −1 of the isovector giant dipole resonance in 208 Pb as well as its electric polarizability α D . Using the Bayesian analysis method, E −1 and α D are found to be mostly determined by the nuclear symmetry energy E sym at about ρ ⋆ =0.05 fm −3 and the isovector nucleon effective mass m ⋆ v at the saturation density. At 90% confidence level, we obtain E sym ( ρ ⋆ )= 16.4 +1.0 −0.9 MeV and m ⋆ v /m= 0.79 +0.06 −0.06 .

We develop a new lattice Hamiltonian method for solving the Boltzmann-Uehling-Uhlenbeck (BUU) equation. Adopting the stochastic approach to treat the collision term and using the GPU parallel computing to carry out the calculations allows for a rather high accuracy in evaluating the collision term, especially its Pauli blocking, leading thus to a new level of precision in solving the BUU equation. Applying this lattice BUU method to study the width of giant dipole resonance (GDR) in nuclei, where the accurate treatment of the collision term is crucial, we find that the obtained GDR width of 208 Pb shows a strong dependence on the in-medium nucleon-nucleon cross section σ ∗ NN . A very large medium reduction of σ ∗ NN is needed to reproduce the measured value of the GDR width of 208 Pb at the Research Center for Nuclear Physics in Osaka, Japan.

Based on the distribution of tidal deformabilities and component masses of binary neutron star merger GW170817, the parametric equation of states (EOS) are employed to probe the nuclear symmetry energy and the properties of neutron star. To obtain a proper distribution of the parameters of the EOS that is consistent with the observation, Bayesian analysis is used and the constraints of causality and maximum mass are considered. From this analysis, it is found that the symmetry energy at twice the saturation density of nuclear matter can be constrained within E sym (2 ρ 0 ) = 34.5 +20.5 −2.3 MeV at 90\% credible level. Moreover, the constraints on the radii and dimensionless tidal deformabilities of canonical neutron stars are also demonstrated through this analysis, and the corresponding constraints are 10.80 km < R 1.4 < 13.20 km and 133< Λ 1.4 <686 at 90\% credible level, with the most probable value of R ¯ 1.4 = 12.60 km and Λ ¯ 1.4 = 500, respectively. With respect to the prior, our result (posterior result) prefers a softer EOS, corresponding to a lower expected value of symmetry energy, a smaller radius and a smaller tidal deformability.

We present a multi-stage model for jet evolution through a quark-gluon plasma within the JETSCAPE framework. The multi-stage approach in JETSCAPE provides a unified description of distinct phases in jet shower contingent on the virtuality. We demonstrate a simultaneous description of leading hadron and integrated jet observables as well as jet v n using tuned parameters. Medium response to the jet quenching is implemented based on a weakly-coupled recoil prescription. We also explore the cone-size dependence of jet energy loss inside the plasma.

The neutron skin thickness ? r np of heavy nuclei is essentially determined by the symmetry energy density slope L(?) at ? c =0.11/0.16 ? 0 ( ? 0 is nuclear saturation density), roughly corresponding to the average density of finite nuclei. The PREX collaboration recently reported a model-independent extraction of ? r 208 np =0.29±0.07 fm for the ? r np of 208 Pb, which suggests a rather stiff symmetry energy E sym (?) with L( ? c )??5 MeV. We demonstrate that the E sym (?) cannot be too stiff and L( ? c )??3 MeV is necessary to be compatible with (1) the ground-state properties and giant monopole resonances of finite nuclei, (2) the constraints on the equation of state of symmetric nuclear matter at suprasaturation densities from flow data in heavy-ion collisions, (3) the largest neutron star (NS) mass reported so far for PSR J0740+6620, (4) the NS tidal deformability extracted from gravitational wave signal GW170817 and (5) the mass-radius of PSR J0030+045 measured simultaneously by NICER. This allow us to obtain 55?�L( ? c )??3 MeV and 0.22?��?r 208 np ??.27 fm, and further E sym ( ? 0 )=34.5±1.5 MeV, L( ? 0 )=85.5±22.2 MeV, and E sym (2 ? 0 )=63.9±14.8 MeV. A number of critical implications on nuclear physics and astrophysics are discussed.

The nuclear symmetry energy is a key quantity in nuclear (astro)physics. It describes the isospin dependence of the nuclear equation of state (EOS), which is commonly assumed to be almost quadratic. In this work, we confront this standard quadratic expansion of the EOS with explicit asymmetric nuclear-matter calculations based on a set of commonly used Hamiltonians including two- and three-nucleon forces derived from chiral effective field theory. We study, in particular, the importance of non-quadratic contributions to the symmetry energy, including the non-analytic logarithmic term introduced by Kaiser [Phys.~Rev.~C \textbf{91}, 065201 (2015)]. Our results suggest that the quartic contribution to the symmetry energy can be robustly determined from the various Hamiltonians employed, and we obtain 1.00(8) MeV (or 0.55(8) MeV for the potential part) at saturation density, while the logarithmic contribution to the symmetry energy is relatively small and model-dependent. We finally employ the meta-model approach to study the impact of the higher-order contributions on the neutron-star crust-core transition density, and find a small 5\% correction.

Starting from chiral two-nucleon (2NF) and chiral three-nucleon (3NF) potentials, we present a detailed study of 17Ne, a Borromean system, with the Gamow shell model which can capture continuum effects. More precisely, we take advantage of the normal-ordering approach to include the 3NF and the Berggren representation to treat bound, resonant and continuum states on equal footing in a complex-momentum plane. In our framework, 3NF is essential to reproduce the Borromean structure of 17Ne, while the continuum is more crucial for the halo property of the nucleus. The two-proton halo structure is demonstrated by calculating the valence proton density and correlation density. The astrophysically interesting 3/ 2 − excited state has its energy above the threshold of the proton emission, and therefore the two-proton decay should be expected from the state.