Neutrino emissivities and mean free paths of degenerate quark matter

Abstract

The neutrino properties of quark matter are investigated by calculating the neutrino emissivities and mean free paths. It is shown that the simple β decay reactions, d → u + e − + v e and u + e − → d + v e , are kinematically allowed due to quark-quark interactions, and that as a consequence quark matter has a neutrino emissivity dramatically larger than that of ordinary neutron star matter, and comparable with that of matter with a pion condensate. In addition, simple β decay reactions are considered due to finite quark masses, β decay of s quarks, and order-of-magnitude estimates of the emissivities from the quark modified URCA process, quark neutrino pair bremsstrahlung and color plasmon decay are given. They all turn out to be relatively small compared with that from the β decay reactions due to quark-quark interactions. The possibility of detecting quark matter inside neutron stars from the recent data obtained by the Einstein X-ray Observatory is discussed. Neutrino mean free paths in quark matter from scattering and absorption processes for both degenerate and nondegenerate neutrinos are also calculated and compared with those of ordinary neutron star matter and matter with a pion condensate. It is found that for a given lepton fraction the mean free paths of degenerate neutrinos are similar for these three types of matter, while they differ by an order of magnitude or more for nondegenerate neutrinos for temperatures less than ∼ 1 MeV.