Unitarity violation in sequential neutrino mixing in a model of extra dimensions

TL;DR

This paper explores how extra spatial dimensions can cause small violations of unitarity in neutrino mixing, due to the effects of an infinite tower of sterile neutrino states.

Contribution

It demonstrates that extra dimensions induce tiny unitarity violations in neutrino mixing matrices, a novel insight into higher-dimensional neutrino models.

Findings

Unitarity can be violated by about 1% due to extra dimensions.

Infinite sterile neutrino states influence neutrino mass matrices.

Small lepton-number violating entries are generated in the model.

Abstract

We investigate the possibility of unitarity violation in the sequential neutrino mixing matrix in a scenario with extra compact spacelike dimensions. Gauge singlet neutrinos are assumed to propagate in one extra dimension, giving rise to an infinite tower of states in the effective four-dimensional theory. It is shown that this leads to small lepton-number violating entries in the neutrino mass matrix, which can violate unitarity on the order of one per cent.