Lepton number violating processes mediated by Majorana neutrinos at hadron colliders

Abstract

We study the lepton number violating like-sign dilepton processes ${h}_{1}{h}_{2}\ensuremath{\rightarrow}{l}^{\ifmmode\pm\else\textpm\fi{}}{l}^{\ensuremath{'}\ifmmode\pm\else\textpm\fi{}}jjX$ and ${h}_{1}{h}_{2}\ensuremath{\rightarrow}{l}^{\ifmmode\pm\else\textpm\fi{}}{l}^{\ensuremath{'}\ifmmode\pm\else\textpm\fi{}}{W}^{\ifmmode\pm\else\textpm\fi{}}X$, mediated by heavy GeV scale Majorana neutrinos. We focus on the resonantly enhanced contributions with a nearly on-mass-shell Majorana neutrino in the $s$ channel. We study the constraints on like-sign dilepton production at the Tevatron and the LHC on the basis of the existing experimental limits on the masses of heavy neutrinos and their mixings ${U}_{\ensuremath{\alpha}N}$ with $\ensuremath{\alpha}={\ensuremath{\nu}}_{e}$, ${\ensuremath{\nu}}_{\ensuremath{\mu}}$, ${\ensuremath{\nu}}_{\ensuremath{\tau}}$. Special attention is paid to the constraints from neutrinoless double beta decay. We note that searches for like-sign ${e}^{\ifmmode\pm\else\textpm\fi{}}{e}^{\ifmmode\pm\else\textpm\fi{}}$ events at Tevatron and LHC may provide evidence of $CP$ violation in the neutrino sector. We also discuss the conditions under which it is possible to extract individual constraints on the mixing matrix elements in a model independent way.