See-saw and lepton flavour violation in SUSY SO(10)

Abstract That μ→e,γ and τ→μ,γ are sensitive probes of SUSY models with a see-saw mechanism is a well accepted fact. Here we propose a ‘top–down’ approach in a general SUSY SO(10) scheme. In this framework, we show that at least one of the neutrino Yukawa couplings is as large as the top Yukawa coupling. This leads to a strong enhancement of these leptonic flavour changing decay rates. We examine two ‘extreme’ cases, where the lepton mixing angles in the neutrino Yukawa couplings are either small (CKM-like) or large (PMNS-like). In these two cases, we quantify the sensitivity of leptonic radiative decays to the SUSY mass spectrum. In the PMNS case, we find that the ongoing experiments at the B-factories can completely probe the spectrum up to gaugino masses of 500 GeV (any tan β). Even in the case of CKM-like mixings, large regions of the parameter space will be probed in the near future, making these two processes leading candidates for indirect SUSY searches.