Flavour violation at the LHC: type-I versus type-II seesaw in minimal supergravity

Abstract

We reconsider the role that the possible detection of lepton flavour violating (LFV) decays of supersymmetric particles at the Large Hadron Collider (LHC) can play in helping reconstruct the underlying neutrino mass generation mechanism within the simplest high-scale minimal supergravity (mSUGRA) seesaw schemes. We study in detail the LFV scalar tau decays at the LHC, assuming that the observed neutrino masses arise either through the pure type-I or the simpler type-II seesaw mechanism. We perform a scan over the mSUGRA parameter space in order to identify regions where lepton flavour violating decays of $\chi^0_2$ can be maximized, while respecting current low-energy constraints, such as those coming from the bounds on Br($\mu \to e \gamma$). We estimate the cross section for $\chi^0_2 \to \chi^0_1 + \tau + \mu $. Though insufficient for a full reconstruction of the seesaw, the search for LFV decays of supersymmetric states at the LHC brings complementary information to that coming from low energy neutrino oscillation experiments and LFV searches.