Testing Radiative Neutrino Mass Models at the LHC

TL;DR

This paper systematically explores various radiative neutrino mass models at the LHC, predicting new particles and analyzing collider constraints to ensure comprehensive search coverage beyond minimal models.

Contribution

It provides a systematic classification of minimal ultraviolet completions for dimension-7 operators and detailed collider analyses for specific models involving vector-like quarks and leptoquarks.

Findings

Predicted new particles constrained by neutrino oscillation data.

Existing LHC limits set lower bounds of approximately 620 GeV for vector-like quarks.

Existing LHC limits set lower bounds of approximately 600 GeV for scalar leptoquarks.

Abstract

The Large Hadron Collider provides us new opportunities to search for the origin of neutrino mass. Beyond the minimal see-saw models a plethora of models exist which realise neutrino mass at tree- or loop-level, and it is important to be sure that these possibilities are satisfactorily covered by searches. The purpose of this paper is to advance a systematic approach to this problem. Majorana neutrino mass models can be organised by SM-gauge-invariant operators which violate lepton number by two units. In this paper we write down the minimal ultraviolet completions for all of the mass-dimension 7 operators. We predict vector-like quarks, vector-like leptons, scalar leptoquarks, a charged scalar, and a scalar doublet, whose properties are constrained by neutrino oscillation data. A detailed collider study is presented for $O_3=LLQ\bar dH$ and $O_8 = L\bar d\bar e^\dagger \bar u^\dagger H$ completions with a vector-like quark $\chi\sim(3, 2, -\frac{5}{6})$ and a leptoquark $\phi\sim(\bar 3,1,\frac{1}{3})$. The existing LHC limits extracted from searches for vector-like fermions and sbottoms/stops are $m_\chi \gtrsim 620$ GeV and $m_\phi\gtrsim 600$ GeV.