Effective theory of a doubly charged singlet scalar: complementarity of neutrino physics and the LHC

TL;DR

This paper introduces a minimal extension of the Standard Model with a doubly charged scalar that links neutrino mass generation and LHC phenomenology, exploring its theoretical framework, experimental constraints, and discovery prospects.

Contribution

It presents a model-independent effective operator for the doubly charged scalar, analyzes neutrino mass generation via two-loop diagrams, and discusses LHC detection strategies for this particle.

Findings

Benchmark points consistent with neutrino data and LFV limits

Potential LHC signatures include same sign leptons and jets

Model demonstrates complementarity of neutrino physics and collider searches

Abstract

We consider a rather minimal extension of the Standard Model involving just one extra particle, namely a single $SU(2)_L$ singlet scalar $S^{++}$ and its antiparticle $S^{--}$. We propose a model independent effective operator, which yields an effective coupling of $S^{\pm \pm}$ to pairs of same sign weak gauge bosons, $W^{\pm} W^{\pm}$. We also allow tree-level couplings of $S^{\pm \pm}$ to pairs of same sign right-handed charged leptons $l^{\pm}_Rl'^{\pm}_R$ of the same or different flavour. We calculate explicitly the resulting two-loop diagrams in the effective theory responsible for neutrino mass and mixing. We propose sets of benchmark points for various $S^{\pm \pm}$ masses and couplings which can yield successful neutrino masses and mixing, consistent with limits on charged lepton flavour violation (LFV) and neutrinoless double beta decay. We discuss the prospects for $S^{\pm \pm}$ discovery at the LHC, for these benchmark points, including single and pair production and decay into same sign leptons plus jets and missing energy. The model represents a minimal example of the complementarity between neutrino physics (including LFV) and the LHC, involving just one new particle, the $S^{\pm \pm}$.