Search for heavy Majorana neutrinos in same-sign dilepton channels in proton-proton collisions at √s = 13 TeV

Abstract

A search is performed for a heavy Majorana neutrino (N), produced in leptonic decay of a W boson propagator and decaying into a W boson and a lepton, with the CMS detector at the LHC. The signature used in this search consists of two same-sign leptons, in any avor combination of electrons and muons, and at least one jet. The data were collected during 2016 in proton-proton collisions at a center-of-mass energy of 13TeV, corresponding to an integrated luminosity of 35.9 fbð€€€1. The results are found to be consistent with the expected standard model background. Upper limits are set in the mass range between 20 and 1600 GeV in the context of a Type-I seesaw mechanism, on jVeNj2, jV Nj2, and jVeNV Nj2=(jVeNj2 + jV Nj2), where V`N is the matrix element describing the mixing of N with the standard model neutrino of avor ` = e; . For N masses between 20 and 1600 GeV, the upper limits on jV`Nj2 range between 2:3 10ð€€€5 and unity. These are the most restrictive direct limits for heavy Majorana neutrino masses above 430 GeV.