Do Neutrino Rest Masses Affect Cosmological Helium Production?

Abstract

It is shown that the possibility of nonzero neutrino rest masses ${m}_{\ensuremath{\nu}}\ensuremath{\approx}10$ ${\mathrm{e}\mathrm{V}/\mathit{c}}^{2}$ does not alter previous predictions of the standard big-bang model for the primordial $^{4}\mathrm{He}$ abundance. Although both left- and right-handed neutrinos could then be present, reactions mediated by the standard Weinberg-Salam-Glashow model extended to include Dirac neutrinos with nonzero rest mass cannot maintain ${\ensuremath{\nu}}_{R}$ in thermal equilibrium.