1210.1523 (Zhi-zhong Xing)

Towards testing the unitarity of the 3X3 lepton flavor mixing matrix in
a precision reactor antineutrino oscillation experiment    [PDF]

Zhi-zhong Xing

The 3X3 Maki-Nakagawa-Sakata-Pontecorvo (MNSP) lepton flavor mixing matrix may be slightly non-unitary if the three active neutrinos are coupled with sterile neutrinos. We show that it is in principle possible to test whether the relation |V_{e1}|^2 + |V_{e2}|^2 + |V_{e3}|^2 = 1 holds or not in a precision reactor antineutrino oscillation experiment, such as the recently proposed Daya Bay II experiment. We explore three categories of non-unitary effects on the 3X3 MNSP matrix: 1) the {\it indirect} effect in the (3+{\bf 3}) flavor mixing scenario where the three heavy sterile neutrinos do not take part in neutrino oscillations; 2) the {\it direct} effect in the (3+\mathbbm{1}) scenario where the light sterile neutrino can oscillate into the active ones; and 3) the {\it interplay} of both of them in the (3+\mathbbm{1}+{\bf 2}) scenario. We find that both the zero-distance effect and flavor mixing factors of different oscillation modes can be used to determine or constrain the sum of |V_{e1}|^2, |V_{e2}|^2 and |V_{e3}|^2 and its possible deviation from one, and the active neutrino mixing angles \theta_{12} and \theta_{13} can be cleanly extracted even in the presence of light or heavy sterile neutrinos. Some useful analytical results are obtained for each of the three scenarios.

View original: http://arxiv.org/abs/1210.1523