Unitarity Tests of the Neutrino Mixing Matrix

Understand

We discuss unitarity tests of the neutrino mixing (PMNS) matrix.

• We show that the combination of solar neutrino experiments, medium-baseline and short-baseline reactor antineutrino experiments make it possible to perform the first direct unitarity test of the PMNS matrix.
• In particular, the measurements of Daya Bay and JUNO (a next generation medium-baseline reactor experiment) will lay the foundation of a precise unitarity test of $|U_{e1}|^2 + |U_{e2}|^2 + |U_{e3}|^2 = 1 $.
• Furthermore, the precision measurement of $\sin^22\theta_{13}$ in both the $\bar{\nu}_e$ disappearance and the $\nu_e$ appearance (from a $\nu_{\mu}$ beam) channels will provide an indirect unitarity test of the PMNS matrix.