Résumé : A search is performed for heavy Majorana neutrinos (N) using an event signature defined by two muons of the same charge and two jets (μ±μ±jj). The data correspond to an integrated luminosity of 19.7 fb-1 of proton-proton collisions at a center-of-mass energy of 8 TeV, collected with the CMS detector at the CERN LHC. No excess of events is observed beyond the expected standard model background and upper limits are set on