Soft supersymmetry breaking as the sole origin of neutrino masses and lepton number violation

Abstract

Abstract We discuss a scenario in which the supergravity induced soft terms, conventionally used for breaking supersymmetry, also lead to non-zero Majorana neutrino masses. The soft terms lead to the spontaneous violation of the lepton number at the gravitino mass scale m 3/2 which in turn leads to (i) the Majorana masses of O $$ \mathcal{O} $$ (m 3/2) for the right-handed neutrinos and (ii) the R-parity breaking at the same scale. The former contributes to light neutrino masses through the type I seesaw mechanism, while the latter adds to it through neutrino-neutralino mixing. Both contributions can scale inversely with respect to m 3/2 given that gaugino and Higgsino masses are also of order m 3/2. Together, these two contributions adequately explain observed neutrino masses and mixing. One realization of the scenario also naturally leads to a μ parameter of O $$ \mathcal{O} $$ (m 3/2). Despite the lepton number symmetry breaking close to the weak scale, the Majoron in the model exhibits very weak coupling to leptons, satisfying existing constraints on Majoron-lepton interactions. The right-handed neutrinos in the model have a large coupling to Higgsinos. This coupling and the relatively large heavy-light neutrino mixing induced through the seesaw mechanism may lead to the observable signals at colliders in terms of displaced vertices.

Keywords

• Baryon/Lepton Number Violation
• Sterile or Heavy Neutrinos
• Supersymmetry