Lepton number violating processes and Majorana neutrinos

TL;DR

This paper reviews lepton number violating processes and their connection to Majorana neutrinos, highlighting experimental sensitivities, especially for intermediate mass neutrinos, and discussing cosmological implications.

Contribution

It provides a comprehensive analysis of lepton number violation, emphasizing the potential of resonant enhancement to detect intermediate mass neutrinos and exploring their cosmological impact.

Findings

Resonant enhancement makes some v processes sensitive to hundred MeV neutrinos.

Most experiments cannot probe light or heavy neutrinos outside the intermediate mass range.

Constraints on sterile neutrinos are discussed with cosmological implications.

Abstract

We discuss some generic properties of lepton number violating (\Lv) processes and their relation to different entries of the Majorana neutrino mass matrix. Present and near future experiments searching for these processes, except the neutrinoless double beta decay, are unable to probe light(eV mass region) and heavy(hundred GeV mass region) neutrinos. On the other hand due to the effect of a resonant enhancement, some of \Lv decays can be very sensitive to the intermediate mass neutrinos with typical masses in hundred MeV region. These neutrinos may appear as admixtures of the three active and an arbitrary number of sterile neutrino species. We analyze the experimental constraints on these massive neutrino states and discuss their possible cosmological and astrophysical implications.