Neutrino-antineutrino pair emission from thermally excited nuclei in stellar collapse

Abstract

We examine the rate of neutrino-antineutrino pair emission by hot nuclei in collapsing stellar cores. The rates are calculated assuming that only allowed charge-neutral Gamow-Teller (GT 0 ) transitions contribute to the decay of thermally excited nuclear states. To obtain the GT 0 transition matrix elements, we employ the quasiparticle random phase approximation extended to finite temperatures within the thermo field dynamics formalism. The decay rates and the energy emission rates are calculated for the sample nuclei 56 Fe and 82 Ge at temperatures relevant to core collapse supernovae.

Thermal quasiparticle random-phase approximation with Skyrme interactions and supernova neutral-current neutrino-nucleus reactions

“…The SkM* force [25] is an example of the first-generation Skyrme parametrizations. In what follows we compare the results of TQRPA calculations with the Skyrme functionals with those performed within the QPM Hamiltonian [14,15]. To distinguish between the two approaches, we refer to them as QPM-TQRPA and Skyrme-TQRPA.…”

“…For comparison, we also show the results from Ref. [15] obtained within the QPM-TQRPA calculations. As expected, the emission rate demonstrates a strong thermal enhancement and from the above discussion it is clear that the main reason for that is the thermal population and the subsequent decay of the GT 0 resonance.…”

“…In Refs. [13][14][15], the TQRPA was applied to compute cross sections and rates for neutral-current neutrinonucleus reactions at the relevant supernova temperatures. It was shown that, although the TQRPA reveals the same thermal effects as reported in Refs.…”

“…In Refs. [13][14][15], the TQRPA calculations were based on a Hamiltonian containing a Woods-Saxon potential supplemented by a pairing interaction and a schematic residual particle-hole interaction of a separable form. This Hamiltonian is usually referred to as the Hamiltonian of the quasiparticle-phonon model (QPM) [16].…”

Neutrino-nucleus reactions in supernovae

“…This approach does not rely on Brink's hypothesis and can be applied to a nucleus with an arbitrary mass number. A more detailed discussion of the method and its application to study weak interaction processes with hot nuclei is given in [6][7][8].…”