Bounds on R-parity Violating Couplings at the Grand Unification Scale from Neutrino Masses

TL;DR

This paper investigates how R-parity violating couplings in supersymmetric models influence neutrino masses, revealing that bounds on these couplings are less strict when considering the full parameter space of the minimal supergravity model.

Contribution

It provides a detailed analysis of neutrino mass dependence on mSUGRA parameters and revises bounds on R-parity violating couplings by including full parameter space effects.

Findings

Bounds on R-parity violating couplings are weaker than previously thought.

Full mSUGRA parameter space reduces the ratio between tree-level and 1-loop neutrino masses.

Parameter regions exist where neutrino mass hierarchy is consistent with observations.

Abstract

We consider the embedding of the supersymmetric Standard Model with broken R-parity in the minimal supergravity (mSUGRA) model. We restrict ourselves to the case of broken lepton number, the B3 mSUGRA model. We first study in detail how the tree-level neutrino mass depends on the mSUGRA parameters. We find in particular a strong dependence on the trilinear supersymmetry breaking A-parameter, even in the vicinity of the mSUGRA SPS1a point. We then reinvestigate the bounds on the trilinear R-parity violating couplings at the unification scale from the low-energy neutrino masses including dominant one-loop contributions. These bounds were previously shown to be very strict, as low as O(10^{-6}) for SPS1a. We show that these bounds are significantly weakened when considering the full mSUGRA parameter space. In particular the ratio between the tree-level and 1-loop neutrino masses is reduced such that it may agree with the observed neutrino mass hierarchy. We discuss in detail how and in which parameter regions this effect arises.