Lower Bound For The Neutrino Magnetic Moment From Kick Velocities Induced At The Birth Of Neutron Stars

We show that the neutrino chirality flip, which can take place in the core of a neutron star at. birth, is an efficient process to allow neutrinos to anisotropically escape, thus providing a to induce the neutron star kick velocities. The process is not subject to the no-go theorem since although the flip from left- to right-handed neutrinos happens at equilibrium, the reverse process does not take place given that right-handed neutrinos do not interact with matter and therefore detailed balance is lost. For simplicity, we model the neutron star core as being made of strange quark matter. We find that the process is efficient when the neutrino magnetic moment is not smaller than 4.7 x 10(-)(15) mu(B), where mu(B) is the Bohr magneton. When this lower bound is combined with the most stringent upper bound, which uses the luminosity data obtained from the analysis of SN 1987A, our results set a range for the neutrino magnetic moment given by 4.7 x 10(-)(15) <= mu(nu)/mu(B)<= (0.1-0.4) x 10(-11). The obtained kick velocities for natal conditions are consistent with the observed ones and span the correct range of radii for typical magnetic field intensities.