Neutrinoless Double Beta Decay and Physics Beyond The Standard Model∗

Neutrinoless double beta decay is a sensitive probe of new physics beyond the standard model. In this review, we begin by describing the various mechanisms for this process and the kind of new physics scenarios where these mechanisms can arise. The present experimental lower bound on the lifetime for ββ0ν is then used to set limits on the parameters of these new physics scenarios. We then consider the positive indications for neutrino masses present in various experiments such as those involving the solar and atmospheric neutrinos as well as the LSND result. Coupled with other astrophysical and cosmological constraints on neutrino masses and mixings, they restrict the allowed profiles for the Majorana neutrino mass matrices considerably. We then show how ongoing searches for ββ0ν decay can confirm or rule out the various scenarios for neutrino masses. In the last section, we present the outlook for observable ββ0ν amplitude in some specific grand unified theories. Invited talk presented at the Workshop on Neutrinoless Double Beta decay and related topics, Trento, Italy; April, 1995 ( to appear in the proceedings ) Work supported by the National Science Foundation Grant No.PHY-9119745 and in part by the Distinguished Faculty Research Fellowship Award by the University of Maryland