Parity Violation in Neutrino Transport and the Origin of Pulsar Kicks

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Abstract
In proto-neutron stars with strong magnetic fields, the neutrino-nucleon scattering/absorption cross sections depend on the direction of neutrino momentum with respect to the magnetic field axis, a manifestation of parity violation in weak interactions. We study the deleptonization and thermal cooling (via neutrino emission) of proto-neutron stars in the presence of such asymmetric neutrino opacities. Significant asymmetry in neutrino emission is obtained because of multiple neutrino-nucleon scatterings. For an ordered magnetic field threading the neutron star interior, the fractional asymmetry in neutrino emission is about 0.006(B/1014 G), corresponding to a pulsar kick velocity of about 200(B/1014 G) km s−1 for a total radiated neutrino energy of 3×1053 ergs.