Role of pairing in the description of Giant Monopole Resonances

TL;DR

This study uses a fully self-consistent QRPA approach with advanced pairing interactions to analyze giant monopole resonances in various nuclei, revealing limitations in current models of nuclear incompressibility.

Contribution

It introduces a comprehensive QRPA framework incorporating density-dependent pairing interactions and neutron-proton asymmetry effects for the first time.

Findings

No single parametrization fits all nuclei accurately.

Soft parametrizations better explain most nuclei, challenging existing incompressibility models.

Inclusion of neutron-proton asymmetry improves resonance descriptions.

Abstract

We compare the results obtained in the framework of the quasiparticle random phase approximation (QRPA) on top of a Hartree-Fock-Bogoliubov (HFB) with the most recent experiments on giant monopole resonances in Pb, Sn, Zr, Sm, Mo and Cd. Our calculations are fully self consistent and the density dependence of pairing interactions is, for the first time in this framework, properly taken into account. In the particle-hole (ph) channel we employ different Skyrme functionals (SLy5, SkM* and Skxs20) while in the particle-particle (pp) channel we make use of density dependent contact interactions. We introduce in the pp channel the recently proposed contact interactions which take into account the neutron-proton asymmetry. We find that no single parametrization is able to reproduce with sufficient accuracy all the nuclei. Since about two-thirds of the nuclei under investigation are better explained with a soft parametrization, this tends to suggest that the currently accepted picture for the incompressibility might require modifications.