Search for heavy Majorana neutrinos in e+/- e+/- + jets and e+/- mu+/- + jets events in proton-proton collisions at sqrt(s) = 8 TeV

We report a search for heavy Majorana neutrinos (N) decaying into a W boson and a lepton using the CMS detector at the Large Hadron Collider. We search for a signature of two same-sign electrons and two jets or a same-sign electron-muon pair and two jets using 19.7~fb$^{-1}$ of data collected during 2012 in proton-proton collisions at a center-of-mass energy of 8 TeV. We find the data to be consistent with the expected standard model background and upper limits are set on $|V_{\ell \mathrm{N}}|^2$, as a function of Majorana neutrino mass from 40-500 GeV$/c^2$, where $V_{\ell \mathrm{N}}$ is the mixing element of the heavy neutrino with the standard model neutrino. The upper limits obtained for $|V_{e \mathrm{N}}|^2$ ($|V_{e \mathrm{N}} V_{\mu \mathrm{N}}^*|$) are 0.022 (0.009) for $m_\mathrm{N} =$ 90 GeV$/c^2$, 0.016 (0.009) for $m_\mathrm{N} =$ 200 GeV$/c^2$, and 0.72 (0.47) for $m_\mathrm{N} =$ 500 GeV$/c^2$. These results extend considerably the regions excluded by previous direct searches.