Neutrino-nucleus scattering off 136Xe

Background: Theoretical estimates of the cross sections for the neutrino-nucleus scattering off relevant nuclei for supernova neutrinos are essential for many applications in neutrino physics and astrophysics. The double-beta-decaying nucleus Xe-136 nucleus is used by the EXO Collaboration in the search for neutrinoless double-beta decay. A ton-scale experiment based on Xe-136 could also be used for studies of supernova neutrinos and/or solar neutrinos. Purpose: The purpose of the present work is, thus, to perform a study of the charged-current and neutral-current nuclear responses to supernova neutrinos for Xe-136. Method: The cross sections are computed by using the well-established framework for studies of semileptonic processes in nuclei introduced by O'Connell, Donnelly, and Walecka [ Phys. Rev. C 6, 719 (1972)]. The nuclear wave functions of the initial and the final nuclear states for the neutral-current neutrino-nucleus scattering in Xe-136 are computed by using the quasiparticle random-phase approximation (QRPA). Similarly, the pnQRPA is adopted to construct the initial and final nuclear states which are relevant for the charged-current reactions. The nuclear responses to supernova neutrinos are subsequently computed by folding the cross sections with appropriate energy spectra for the incoming neutrinos. Results: We present results for the cross sections of the charged-current and neutral-current neutrino and antineutrino scatterings off 136Xe. Nuclear responses to supernova neutrinos are also given. For the considered scenario for the neutrino mixing we have found that neutrino interactions with matter and so-called collective neutrino oscillations enhance significantly the neutrino and antineutrino flux-averaged cross sections. Conclusions: We have found that for the charged-current and neutral-current neutrino scatterings off Xe-136 transitions mediated by the 1(+) multipole are the most important ones. However, for the charged-current antineutrino channel 0(+) and 1(+) transitions are largely suppressed due to the large neutron excess. Transitions to 1- and 2-final nuclear states are thus relatively more important for the charged-current antineutrino scattering.