Probing heavy Majorana neutrinos and the Weinberg operator through vector boson fusion processes in proton-proton collisions at $\sqrt{s}$ = 13 TeV

TL;DR

This paper presents the first LHC search using vector boson fusion to probe heavy Majorana neutrinos and the Weinberg operator, setting new constraints on their properties with 138 fb$^{-1}$ of data at 13 TeV.

Contribution

It introduces a novel vector boson fusion approach to study heavy Majorana neutrinos and the Weinberg operator at the LHC, providing the first collider constraints on these phenomena.

Findings

Most stringent LHC constraints on heavy neutrino mixing above 650 GeV.

First collider upper limit on the effective Majorana neutrino mass from the Weinberg operator.

Results consistent with Standard Model predictions.

Abstract

The first search exploiting the vector boson fusion process to probe heavy Majorana neutrinos and the Weinberg operator at the LHC is presented. The search is performed in the same-sign dimuon final state using a proton-proton collision data set recorded at $\sqrt{s}$ = 13 TeV, collected with the CMS detector and corresponding to a total integrated luminosity of 138 fb$^{-1}$. The results are found to agree with the predictions of the standard model. For heavy Majorana neutrinos, constraints on the squared mixing element between the muon and the heavy neutrino are derived in the heavy neutrino mass range 50 GeV-25 TeV; for masses above 650 GeV these are the most stringent constraints from searches at the LHC to date. A first test of the Weinberg operator at colliders provides an observed upper limit at 95% confidence level on the effective $\mu\mu$ Majorana neutrino mass of 10.8 GeV.