Neutrino mass from higher than d=5 effective operators in SUSY, and its test at the LHC

TL;DR

This paper explores how higher-dimensional operators in supersymmetric models can generate neutrino masses, discusses their potential signatures at the LHC, and examines the testability of lepton number violation through collider experiments.

Contribution

It systematically analyzes higher than d=5 operators for neutrino mass generation in SUSY, focusing on d=7 operators and their collider phenomenology, including observable signatures at the LHC.

Findings

Certain d=7 operators lead to see-saw scenarios with extra neutral fermions.

Heavy mediators can be produced at the LHC and may produce displaced vertices.

Direct observation of lepton number violation at LHC remains challenging.

Abstract

We discuss neutrino masses from higher than d=5 effective operators in a supersymmetric framework, where we explicitly demonstrate which operators could be the leading contribution to neutrino mass in the MSSM and NMSSM. As an example, we focus on the d=7 operator L L H_u H_u H_d H_u, for which we systematically derive all tree-level decompositions. We argue that many of these lead to a linear or inverse see-saw scenario with two extra neutral fermions, where the lepton number violating term is naturally suppressed by a heavy mass scale when the extra mediators are integrated out. We choose one example, for which we discuss possible implementations of the neutrino flavor structure. In addition, we show that the heavy mediators, in this case SU(2) doublet fermions, may indeed be observable at the LHC, since they can be produced by Drell-Yan processes and lead to displaced vertices when they decay. However, the direct observation of lepton number violating processes is on the edge at LHC.