Probing minimal supergravity in the type-I seesaw mechanism with lepton flavour violation at the CERN LHC

TL;DR

This paper investigates how lepton flavour violation processes at the CERN LHC can provide insights into the parameters of the minimal supergravity type-I seesaw mechanism, potentially revealing properties of right-handed neutrinos.

Contribution

It computes LFV decay branching ratios within a minimal supergravity type-I seesaw model and explores their sensitivity to unknown parameters, proposing methods to extract right-handed neutrino information.

Findings

LFV decay ratios correlate with neutrino oscillation parameters.

LFV processes can potentially reveal right-handed neutrino properties.

Certain scenarios allow extraction of unknown seesaw parameters from LFV measurements.

Abstract

The most general supersymmetric seesaw mechanism has too many parameters to be predictive and thus can not be excluded by any measurements of lepton flavour violating (LFV) processes. We focus on the simplest version of the type-I seesaw mechanism assuming minimal supergravity boundary conditions. We compute branching ratios for the LFV scalar tau decays, ${\tilde \tau}_2 \to (e,\mu) + \chi^0_1$, as well as loop-induced LFV decays at low energy, such as $l_i \to l_j + \gamma$ and $l_i \to 3 l_j$, exploring their sensitivity to the unknown seesaw parameters. We find some simple, extreme scenarios for the unknown right-handed parameters, where ratios of LFV branching ratios correlate with neutrino oscillation parameters. If the overall mass scale of the left neutrinos and the value of the reactor angle were known, the study of LFV allows, in principle, to extract information about the so far unknown right-handed neutrino parameters.