Lepton Number Violating Processes Mediated by Majorana Neutrinos at Hadron Colliders

We study the Lepton number violating like-sign dilepton processes $h_1 h_2 \to l^\pm l^{\prime \pm} jj X$ and $h_1 h_2 \to l^\pm l^{\prime \pm} W^\pm X$, 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 $U_{\alpha N}$ with $\alpha = \nu_{e}, \nu_{\mu}, \nu_{\tau}$. Special attention is paid to the constraints from neutrinoless double beta decay. We note that searches for like-sign $e^{\pm} e^{\pm}$ events at Tevatron and LHC may shed light on CP-violation in 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.