The Contribution from Neutrino Yukawa Couplings to Lepton Electric Dipole Moments

Abstract

To explain the observed neutrino masses through the seesaw mechanism, a supersymmetric generalization of the Standard Model should include heavy right-handed neutrino supermultiplets. Then the neutrino Yukawa couplings can induce CP violation in the lepton sector. In this paper, we compute the contribution of these CP violating terms to lepton electric dipole moments. We introduce a new formalism that makes use of supersymmetry to expose the GIM cancellations. In the region of small tan beta, we find a different result from that given previously by Ellis, Hisano, Raidal, and Shimizu. We confirm the structure found by this group, but with a much smaller overall coefficient. In the region of large tan beta, we recompute the leading term that has been identified by Masina and confirm her result.We discuss the implications of these results for constraints on the neutrino Yukawa couplings.