Journal Article

A framework for testing leptonic unitarity by neutrino oscillation experiments

Fong, Chee Sheng, Minakata, Hisakazu, Nunokawa, Hiroshi

2017

Overview

A bstract If leptonic unitarity is violated by new physics at an energy scale much lower than the electroweak scale, which we call low-scale unitarity violation, it has different characteristic features from those expected in unitarity violation at high-energy scales. They include maintaining flavor universality and absence of zero-distance flavor transition. We present a framework for testing such unitarity violation at low energies by neutrino oscillation experiments. Starting from the unitary 3 active plus N (arbitrary positive integer) sterile neutrino model we show that by restricting the active-sterile and sterile-sterile neutrino mass squared differences to ≳ 0.1 eV 2 the oscillation probability in the (3 + N ) model becomes insensitive to details of the sterile sector, providing a nearly model-independent framework for testing low-scale unitarity violation. Yet, the presence of the sterile sector leaves trace as a constant probability leaking term, which distinguishes low-scale unitarity violation from the high-scale one. The non-unitary mixing matrix in the active neutrino subspace is common for the both cases. We analyze how severely the unitarity violation can be constrained in ν e -row by taking a JUNO-like setting to simulate medium baseline reactor experiments. Possible modification of the features of the (3 + N ) model due to matter effect is discussed to first order in the matter potential.

• Publisher: Springer Berlin Heidelberg,Springer Nature B.V
• Subject: Classical and Quantum Gravitation / Computer simulation / Constraints / Elementary Particles / Flavours / High energy physics / Integers / Low energy / Neutrinos / Physics / Physics and Astronomy / Quantum Field Theories / Quantum Field Theory / Quantum Physics / Reactors / Regular Article - Theoretical Physics / Relativity Theory / String Theory / Subspaces