Abstract
Nonunitary neutrino mixing in the light neutrino sector is a direct consequence of type-I seesaw neutrino mass models. In these models, light neutrino mixing is described by a submatrix of the full lepton mixing matrix and, then, it is not unitary in general. In consequence, neutrino oscillations are characterized by additional parameters, including new sources of $CP$ violation. Here we perform a combined analysis of short and long-baseline neutrino oscillation data in this extended mixing scenario. We did not find a significant deviation from unitary mixing, and the complementary data sets have been used to constrain the nonunitarity parameters. We have also found that the T2K and NOvA tension in the determination of the Dirac $CP$-phase is not alleviated in the context of nonunitary neutrino mixing.
Highlights
Current neutrino oscillation data [1,2,3] implies that neutrinos are massive particles
We have found that the T2K and NOvA tension in the determination of the Dirac CP-phase is not alleviated in the context of nonunitary neutrino mixing
We show that a combined analysis of the data of the short-baseline appearance experiments NOMAD and NuTeV and the long-baseline experiments Main Injector Neutrino Oscillation Search (MINOS)= MINOSþ, T2K and NOvA allows us to constrain all the nonunitarity parameters
Summary
Current neutrino oscillation data [1,2,3] implies that neutrinos are massive particles. A convenient parametrization of the nonunitary submatrix is obtained by multiplying the standard unitary three-neutrino mixing matrix on the left with a triangular matrix [28] This parametrization is independent of the number of new particles [28]. Seesaw mechanisms with relatively light new states [29] could account for the observed short-baseline anomalies [30,31,32,33,34,35,36,37,38,39,40,41], here we consider only relatively heavy new states, such that the nonunitarity of the mixing matrix is mainly constrained by neutrino oscillation data.
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