Enrico Bertuzzo (University of Modena and Reggio Emilia)

Sterile dipoles

Sterile dipoles (i.e. dipole operators involving sterile neutrinos only) appear at the level of dimension 5 once the Standard Model Effective Field Theory (SMEFT) is extended to include right handed neutrinos at or below the electroweak scale. Since these dipoles automatically involve two different Weyl fermions because of the antisymmetry of the spinor structure appearing in the operator, they generate the radiative decay of the heavier sterile neutrino into the lighter and a photon. This signature can be bounded by beam dump, accelerators and astrophysical data and, more interestingly, can in principle be probed at future "intensity frontier" experiments. In this talk I will first discuss in detail how the sterile dipoles emerge and the current bounds on their Wilson coefficient. I will then show the sensitivity of future experiments on their parameter space and discuss possible future directions.