Neutrino Mass and $\mu \rightarrow e + \gamma $ from a Mini-Seesaw

TL;DR

This paper explores a low-scale seesaw model for neutrino masses involving light sterile neutrinos, analyzing experimental bounds and predicting observable signals in mu to e gamma decay within current experimental reach.

Contribution

It introduces the mini-seesaw mechanism with light sterile neutrinos and studies their experimental constraints and potential signals.

Findings

Viable parameter space for light sterile neutrinos exists.

Predicted BR(  e + \u03b3) is within MEG experiment sensitivity.

Key observables can be just below current experimental limits.

Abstract

The recently proposed "mini-seesaw mechanism" combines naturally suppressed Dirac and Majorana masses to achieve light Standard Model neutrinos via a low-scale seesaw. A key feature of this approach is the presence of multiple light (order GeV) sterile-neutrinos that mix with the Standard Model. In this work we study the bounds on these light sterile-neutrinos from processes like \mu ---> e + \gamma, invisible Z-decays, and neutrinoless double beta-decay. We show that viable parameter space exists and that, interestingly, key observables can lie just below current experimental sensitivities. In particular, a motivated region of parameter space predicts a value of BR(\mu ---> e + \gamma) within the range to be probed by MEG.