Search for heavy Majorana neutrinos in mu+mu+[mu-mu-]+jets and e+e+[e-e-]+jets events in pp collisions at sqrt(s) = 7 TeV

TL;DR

This paper reports a search for heavy Majorana neutrinos in proton-proton collisions at 7 TeV, using same-sign lepton and jet signatures, setting the first direct limits on neutrino mixing for masses above 90 GeV.

Contribution

It provides the first direct experimental upper limits on heavy Majorana neutrino mixing for masses greater than 90 GeV using CMS data.

Findings

No excess events observed beyond standard model background.

Set upper limits on the mixing parameter |V_{ell N}|^2 as a function of neutrino mass.

First direct constraints on heavy Majorana neutrinos for masses above 90 GeV.

Abstract

A search is performed for heavy Majorana neutrinos (N) using an event signature defined by two same-sign charged leptons of the same flavour and two jets. The data correspond to an integrated luminosity of 4.98 inverse femtobarns of pp collisions at a centre-of-mass energy of 7 TeV collected with the CMS detector at the Large Hadron Collider. No excess of events is observed beyond the expected standard model background and therefore upper limits are set on the square of the mixing parameter, abs(V[ell N]) squared, for ell = e, mu, as a function of heavy Majorana-neutrino mass. These are the first direct upper limits on the heavy Majorana-neutrino mixing for m[N] > 90 GeV.