Seminar “Nuclear Theory”

Date and Time: Monday, 19 October 2020, at 3:30 PM

Venue: Online conference in Zoom, Bogoliubov Laboratory of Theoretical Physics

Seminar topic: «Three-body soft dipole mode and astrophysical applications»

Authors: L. V. Grigorenko^1,2,3, Yu. L. Parfenova¹, N. B. Shulgina^3,4, M.V. Zhukov<sup>5

1</sup> – FLNR, JINR, Dubna, Russia
² – NRN University “MEPhI”, Moscow, Russia
³ – NRC “Kurchatov Institute” Moscow, Russia
⁴ – BLTP, JINR, Dubna, Russia
⁵ – Chalmers University of Technology, Goteborg, Sweden

Speaker: N. B. Shulgina

Abstract:

Theoretical methods have been developed that allow correct describing of soft dipole excitations in a wide range of energies: from very small ∼10-500 keV, which are important for nuclear astrophysics, to ∼10 MeV, where the dipole excitations are no longer soft. For the first time, correct low-energy asymptotics for E1 strength functions of three-body radiative captures “core + n + n” and “core + p + p” and the corresponding correct low-temperature asymptotics of astrophysical rates of three-body radiative captures are obtained. The results for the studied cases of ⁶He and ¹⁷Ne differ sharply (by orders of magnitude) from all previously obtained results. It is shown that for radiative captures of “core + n + n” the dynamics of the n-n interaction in the final state dominates, while for radiative captures of “core + p + p” the dynamics of interaction in the subsystem “core + p” dominates, which is well described in the semi-analytical model with a simplified three-body Hamiltonian. A completely analytical generalization of the method of asymptotic normalization coefficients is constructed for the case of nonresonant three-body proton captures at astrophysical energies. The high accuracy of this approximation is substantiated.

(to be nominated for the JINR Prize 2020)