Single β and double 0νββ decays with Majorana spinors

We first show that the Majorana spinors which are eigenspinors to the charge conjugation operator, C = igamma(2)K, with K standing for complex conjugation, are completely different species but the Dirac spinors which are eigenspinors to the parity operator, P = gamma(0). The difference is that while P eigenspinors propagate in accord with the Dirac equation, C eigenspinors are static. This is due to the fact that while upon boost gamma(0) transforms as B(p)gamma(0)B(p)(-1) = p/m, under same transformation C remains static because of B(P)gamma(2)KB(p)(-1) = gamma(2). In order to escape above dilemma one has M two options. To either give up the concept of C eigenspinors and restrict calculus to two dimensional Weyl spinors with Grassmann number components, a path pursued by the literature, or, exploit the fact that in eight spinorial dimensions, (8d), one can construct commuting C and P operators and achieve Majorana spinor propagation there, a path taken by the present work. We express (8d) Majorana traces of single beta and double 0nubetabeta decays in terms of standard Dirac traces and find the neutrino mass to drop from the single beta, and re-appear in the 0nubetabeta trace, an intriguing and in principle experimentally testable footprint of Majorana-ness of massive neutrino.