Low energy neutrino elastic scattering and supernova explosions

Abstract

COLGATE AND WHITE¹ have proposed that neutrinos could transport energy outwards during the gravitational collapse of a star, thus initiating a supernova explosion. Detailed calculations by Wilson² seemed to rule out this possibility, but Freedman³ pointed out in the context of unified gauge theories of weak and electromagnetic interactions that there could be both a large neutrino–neutron elastic scattering cross section and a very large coherent neutrino–heavy nucleus cross section. Wilson⁴ has recently recalculated the collapse of an iron core formed at the end of a stellar evolution from massive stars and shown that the calculations do simulate an explosion, and that a stronger explosion results from smaller coherent scattering off heavy nuclei. This surprising result arises because a smaller cross section allows more neutrinos to escape, lowering the pressure and thereby letting the neutron core reach a higher density before the outward shock wave is formed. We have calculated neutrino–nucleon and neutrino–heavy nucleus neutral current cross sections in weak SU(2)×U(1) and compared with those of the standard unified theory. Important differences are found which could make simulated supernova explosions easier to obtain. Possible experiments to test the two theories are outlined here.