# Quasi-Dirac neutrinos at the LHC

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## Abstract

Lepton number violation is searched for at the LHC using same-sign leptons plus jets. The standard lore is that the ratio of same-sign lepton to opposite-sign lepton events, *R* _{ ll }, is equal to *R* _{ ll } = 1 (*R* _{ ll } = 0) for Majorana (Dirac) neutrinos. We clarify under which conditions the ratio *R* _{ ll } can assume values different from 0 and 1, and we argue that the precise value 0 *< R* _{ ll } *<* 1 is controlled by the mass splitting versus the width of the quasi-Dirac resonances. A measurement of *R* _{ ll } = 0*,* 1 would then contain valuable information about the origin of neutrino masses. We consider as an example the inverse seesaw mechanism in a left-right symmetric scenario, which is phenomenologically particularly interesting since all the heavy states in the high energy completion of the model could be within experimental reach. A prediction of this scenario is a correlation between the values of *R* _{ ll } and the ratio between the rates for heavy neutrino decays into standard model gauge bosons, and into three body final states *ljj* mediated by off-shell *W* _{ R } exchange.

## Keywords

Beyond Standard Model Neutrino Physics## Notes

**Open Access**

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