Lepton number violation in theories with a large number of Standard Model copies

TL;DR

This paper investigates lepton number violation in theories with many Standard Model copies, showing that potential large violations are suppressed by a compensation mechanism, making observable effects negligible.

Contribution

It demonstrates that in theories with numerous Standard Model copies, lepton number violation remains suppressed due to a specific cancellation mechanism among neutrino states.

Findings

LNV processes are suppressed below experimental detection levels.

A compensation mechanism cancels contributions from different neutrino states.

TeV scale LNV operators do not lead to large observable violations.

Abstract

We examine lepton number violation (LNV) in theories with a saturated black hole bound on a large number of species. Such theories have been advocated recently as a possible solution to the hierarchy problem and an explanation of the smallness of neutrino masses. The violation of lepton number can be a potential phenomenological problem of this N-copy extension of the Standard Model as due to the low quantum gravity scale black holes may induce TeV scale LNV operators generating unacceptably large rates of LNV processes. We show, however, that this does not happen in this scenario due to a specific compensation mechanism between contributions of different Majorana neutrino states to these processes. As a result rates of LNV processes are extremely small and far beyond experimental reach, at least for the left-handed neutrino states.