Microscopic optical potential for exotic isotopes from chiral effective field theory

Abstract

We compute the isospin-asymmetry dependence of microscopic optical model potentials from realistic chiral two-and three-body interactions over a range of resolution scales Λ 400 − 500 MeV. We show that at moderate projectile energies, Einv = 110 − 200 MeV, the real isovector part of the optical potential changes sign, a phenomenon referred to as isospin inversion. We also extract the strength and energy dependence of the imaginary isovector optical potential and find no evidence for an analogous phenomenon over the range of energies, E ≤ 200 MeV, considered in the present work. Finally, we compute for the first time the leading corrections to the Lane parametrization for the isospin-asymmetry dependence of the optical potential and observe an enhanced importance at low scattering energies.Introduction -The structure and dynamics of neutronrich nuclei are key inputs for modeling neutron stars, core-collapse supernovae and r-process nucleosynthesis [1][2][3][4][5][6][7][8]. Elucidating the properties of highly isospinasymmetric nuclear matter is therefore a priority in lowenergy nuclear science research and a major motivation for the development of next-generation radioactive ion beam (RIB) facilities. Microscopic many-body methods [9-11] with chiral two-and three-body forces have been successful in describing the bound-state properties of neutron-rich matter. Complementary and consistent nuclear reaction models are under development [12][13][14], and of these, global optical potentials aim to address the broadest theory needs for interpreting RIB scattering experiments and simulating r-process nucleosynthesis. In fact, current modeling of the strong r-process favors a cold scenario in binary neutron star mergers [6][7][8][15][16][17], where mass transfer to highly neutron-rich isotopes occurs and freeze-out is achieved more rapidly, which enhances the importance of radiative neutron capture processes in determining the final abundance pattern of rprocess elements [18].

Green's Function Techniques for Infinite Nuclear Systems

“…In terms of isospin dependence, the results also agree with previously reported outcomes in the SCGF approach [64], and in other many-body calculations [93][94][95]. In symmetric nuclear matter, the single-particle potential has a minimum at low momenta close to U k=0 ≈ −60 MeV, and increases steeply with momenta.…”

Equation of state of nuclear and neutron matter at third-order in perturbation theory from chiral effective field theory

“…If Refs. [50,51] we employed low-momentum chiral twoand three-body forces at second-order in perturbation theory and found very good agreement with the isoscalar and isovector real components of the optical potential compared to phenomenology [52][53][54] for energies E 200 MeV. …”

Asymmetry dependence of Gogny-based optical potential

“…Higher-order versions of Lane prescription have been investigated by Holt et al [12] and could be relevant in the 48 Ca case. Nevertheless, one has to keep in mind that formally NSM potential contains Lane-inconsistent terms in the second order terms.…”

“…For evaluation purposes, optical potential is often fitted in order to reproduce a consistent set of reaction observables. Whenever experimental data are not available, one can ideally rely on more microscopic approaches such as Nuclear Field Theory [5,6], Energy Density Functionals (EDF) [7,8,9,10], ab initio approaches [11,12] or mixed approaches such as g-matrix effective interaction folded with EDF density [13,14]. Moreover microscopic approaches can yield a physical guidance for new parametrizations of phenomenological potentials providing form factors for volume and surface parts of the potential, energy dependence, nonlocality shape and parameters, dependence on the isospin asymmetry of the target nucleus.…”