Rare meson decays with three pairs of quasi-degenerate heavy neutrinos

TL;DR

This paper explores how specific arrangements of quasi-degenerate heavy neutrinos in a Low Scale Seesaw model can influence rare meson decays, offering new insights and constraints on neutrino mixing parameters.

Contribution

It introduces a novel scenario with three pairs of quasi-degenerate heavy neutrinos affecting rare meson decays and provides new experimental constraints on neutrino mixing.

Findings

Possible new decay channels depending on on-shell pairs

Constraints on muon-heavy neutrino mixing parameters

Conditions for maximal CP violation

Abstract

We consider a scenario of Low Scale Seesaw where the masses of its heavy Majorana neutrinos are arranged in a pattern of three pairs of quasi degenerate ones, in the range of O(1-6 GeV). Since they can violate lepton number by two units, they contribute to rare decays of Ds and Bc mesons, providing, besides, conditions for maximal CP violation. We found that new phenomenology is possible depending on how many of on-shell pairs mediate these decays. In particular, we present new constraints on muon-heavy neutrinos mixing parameters.