WIDG Seminar: Patrick Bolton, University College London, “Neutrinoless Double Beta Decay Versus Direct Search Probes of the Inverse Seesaw Mechanism”

One explanation for the light active neutrino masses is the so-called inverse seesaw mechanism. This introduces two sets of Standard Model-singlet states with opposite lepton number. The attractive feature of such a scenario is that the size of lepton number violation is proportional to a small ‘technically natural’ parameter directly related to the mass splitting between the introduced sterile states. Consequently, active-sterile mixings can be sizeable and be probed by direct search experiments for sterile neutrino masses below a TeV.
I will first outline a simple phenomenological parametrisation of this model in which the canonical and inverse seesaws are limiting cases. I will then compare the constraints on this model from direct searches to those from neutrinoless double beta decay - a crucial consideration is whether the splitting between the sterile neutrino pairs is small (behaving like a single pseudo-Dirac neutrino) or large (behaving like two Majorana neutrinos). Finally, I will briefly look at the future prospects of the Project 8 experiment in probing sterile neutrinos in the keV range through spectral distortions in the beta decay spectrum. The shape of such spectral distortions could give clues to extensions to the Standard Model, such as a low-scale left-right symmetry.
Please RSVP for lunch using link below: