Looking for lepton flavour violation in supersymmetry at the LHC

Abstract

We consider models of supersymmetry which can incorporate sizeable mixing between different generations of sfermions. While the mixing is constrained by the non-observation of various flavour changing neutral current (FCNC) processes, there exist regions of SUSY parameter space where the effects of such mixing can be probed at colliders. In this work, we explore this possibility by focussing on the slepton sector. The sleptons are produced through cascade decays in direct neutralino-chargino ($\chi_2^0\chi_1^\pm$) pair production at the LHC. The final state is characterized by 3 leptons and missing energy. We probe the lepton flavour violating (LFV) vertex originating from $\chi_2^0$ decay and identify a distinct and unambiguous combination of the tri-lepton final state which include a lepton pair with same flavour and same sign (SFSS) in addition to a pair with opposite flavour and opposite sign (OFOS). This combination of tri-lepton final state containing both OFOS and SFSS pairs, can not only suppress the SM background but can also differentiate the flavour violating decays of $\chi_2^0$ from its corresponding flavour conserving decays. We present results for various signal benchmark points taking into account background contributions assuming two luminosity options (100 fb$^{-1}$ and 1000 fb$^{-1}$) for LHC Run 2 experiment.