LHC Run I bounds on minimal lepton flavour violation in Type-III see-saw: a case study

Abstract

Abstract In minimal lepton flavour violation Type-III see-saw models the flavour structure of the couplings of the triplet fermions to the Standard Model leptons can be reconstructed from the neutrino mass matrix and lepton number violation is very suppressed. Here, we explore the possibility of imposing bounds on this class of models with results of existing LHC searches and we quantify how the information on flavour and charge of the produced leptons is important for maximal sensitivity. With this aim we obtain the bounds which can be derived from the Run I search for events which contain two charged leptons (either electron or muons of equal or opposite sign), two jets from a hadronically decaying W boson and large missing transverse momentum. We find that using the information on charge and flavour of the leptons in the above final state it is possible to unambiguously rule out this scenario with triplet masses lighter than 300 GeV at 95% CL. The same analysis allows to exclude triplet masses up to 480 GeV at 95% CL for normal ordering of neutrino masses and specific values of a Majorana CP phase currently undetermined by neutrino physics. We also show that it is not possible to put an unambiguous bound on the mass of the new states if the flavor and charge information is not condsidered.

Keywords

• Beyond Standard Model
• Neutrino Physics