Lepton flavor violation and non-unitary lepton mixing in low-scale type-I seesaw

TL;DR

This paper investigates how low-scale seesaw models can produce significant lepton flavor violation and non-standard neutrino interactions, with potential observable effects in upcoming experiments, while remaining consistent with current constraints.

Contribution

It analyzes the relationship between non-unitarity effects and LFV constraints in low-scale seesaw models, highlighting the possibility of sizeable NSI parameters compatible with experimental limits.

Findings

NSI parameters can reach percent levels in some models.

LFV rates like  o e \,  \,  are within current experimental bounds.

Upcoming neutrino experiments can test these effects through LFV and universality measurements.

Abstract

Within low-scale seesaw mechanisms, such as the inverse and linear seesaw, one expects (i) potentially large lepton flavor violation (LFV) and (ii) sizeable non-standard neutrino interactions (NSI). We consider the interplay between the magnitude of non-unitarity effects in the lepton mixing matrix, and the constraints that follow from LFV searches in the laboratory. We find that NSI parameters can be sizeable, up to percent level in some cases, while LFV rates, such as that for \mu -> e \gamma, lie within current limits, including the recent one set by the MEG collaboration. As a result the upcoming long baseline neutrino experiments offer a window of opportunity for complementary LFV and weak universality tests.