Double beta decay, supersymmetry and lepton number violation

Abstract

Neutrinoless double beta (0νββ) decay violates lepton number and is therefore a sensitive probe of physics beyond the standard model. Limits from 0νββ decay are usually expressed in terms of limits on the Majorana neutrino mass, the best experiment now giving 〈 m ν 〉 ≤ 0.5 eV. However, in supersymmetric extensions of the SM there can be other sources of lepton number violation than the neutrino mass, the best-known example being R P -violation. 0νββ decay provides the most stringent limits on certain R ̷ p MSSM parameters, ruling out first generation squarks as a possible explanation of the recent HERA high Q 2-events. Furthermore, current low-energy constraints on and future collider phenomenology of ( B − L) violating sneutrino masses are discussed. As has been proven recently such a ( B − L) violating sneutrino mass is a necessary ingredient of any supersymmetric model with finite Majorana neutrino masses.