title: New Ambiguity in Probing CP Violation in Neutrino Oscillations.
abstract: If neutrinos get mass via the seesaw mechanism the mixing matrix describing neutrino oscillations can be effectively nonunitary. We show that in this case the neutrino appearance probabilities involve a new CP phase ϕ associated with nonunitarity. This leads to an ambiguity in extracting the "standard" three-neutrino phase δ_{CP}, which can survive even after neutrino and antineutrino channels are combined. Its existence should be taken into account in the planning of any oscillation experiment aiming at a robust measurement of δ_{CP}.
authors.affiliation: Departamento de Física, Centro de Investigación y de Estudios Avanzados del IPN, Apdo. Postal 14-740, 07000 Mexico, DF, Mexico.
authors.forename: O G
authors.initials: OG
authors.lastname: Miranda
authors.affiliation: AHEP Group, Institut de Física Corpuscular-C.S.I.C./Universitat de València, Parc Cientific de Paterna, C/Catedratico José Beltrán, 2 E-46980 Paterna (València), Spain.
authors.forename: M
authors.initials: M
authors.lastname: Tórtola
authors.affiliation: AHEP Group, Institut de Física Corpuscular-C.S.I.C./Universitat de València, Parc Cientific de Paterna, C/Catedratico José Beltrán, 2 E-46980 Paterna (València), Spain.
authors.forename: J W F
authors.initials: JW
authors.lastname: Valle