Nonunitarity effects in a realistic low-scale seesaw model

We analyze the structure of the nonunitary leptonic mixing matrix in the inverse seesaw model with heavy singlets accessible at the LHC. In this model, unlike in the usual TeV seesaw scenarios, the low-scale right-handed neutrinos do not suffer from naturalness issues. Underlying correlations among various parameters governing the nonunitarity effects are established, which leads to a considerable improvement of the generic nonunitarity bounds. In view of this, we study the discovery potential of the nonunitarity effects at future experiments, focusing on the sensitivity limits at a neutrino factory.

Figure 1

Sensitivity limits at 90% C.L. on ${\eta }_{\mu \tau }$ in the inverse seesaw model as a function of $L$ corresponding to the first two (mandatory) terms in Eq. (16).

Figure 2

Scheme of the potentially interesting LHC signature with three charged leptons and missing energy emerging at appreciable rates in the model under consideration.