Supersymmetric Grand Unification and Lepton Universality in K-> l \nu Decays

Understand

Motivated by the prospects for an improved test of lepton universality in K -> l \nu decays by the NA62 experiment at CERN, we study predictions for the possible lepton non-universality in K -> l \nu decays in supersymmetric models.

• Violations of \mu-e universality in this process may originate from mixing effects in the right-handed slepton sector, providing a unique window into this aspect of supersymmetric flavour physics in the large-\tan\beta region.
• Minimal unification scenarios with universal soft supersymmetry-breaking terms at the GUT scale would predict negligible violation of lepton universality.
• However, lepton non-universality may be observable in non-minimal grand unified models with higher-dimensional terms contributing to fermion masses, in which case renormalization effects above the GUT scale may enhance the mixing among the right-handed sleptons.