Neutrino and Antineutrino captures on 18O within QRPA models

Abstract

In this work we have evaluated the neutrino (NS) and antineutrino (AS) scattering cross sections on 18O and the inclusive muon capture rates at low energies within the Quasiparticle Random Phase Approximation (QRPA) and Projected QRPA (PQRPA)models.We present the first study of 18O(νe, e−)18F and 18O(¯νe, e+)18N cross sections. These reactions are an important nuclear input for astrophysical calculations such as the CNO cycle. We have employed the weak formalism developed in Krmpoti´c et al. (Phys Rev C 71:044319, 2005) to analyze neutrino/antineutrino-nucleus scattering. Within this formalism, the nuclear residual interaction is described by δ-force previously employed to evaluate single and double beta decays in QRPA models. The adopted parametrization leads to good results for the inclusive muon capture: we reproduce the available experimental data for the rate and the Gamow–Teller strength in 18F. We compared our results for the NS and AS cross sections on 18O with other theoretical evaluations on 16O, since there are noexperimental data available for the processes on 18O. We noticed that the cross sections present a similar behavior as a function of the neutrino/antineutrino energy. For NS and AS we observed that the PQRPA procedure yields cross sections smaller than QRPA. We show that the Pauli blocking has an important role in the distribution of the partial contributions and the presence of two neutrons over the closed shell yields to higher NS cross sections than the AS cross sections. ForNS and AS, the largest contribution comes from allowed and first-forbidden transitions, respectively.