We derive predictions for the Dirac phase δ\documentclass[12pt]{minimal}
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\begin{document}$$\delta $$\end{document} present in the 3×3\documentclass[12pt]{minimal}
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\begin{document}$$3\times 3$$\end{document} unitary neutrino mixing matrix U=Ue†Uν\documentclass[12pt]{minimal}
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\begin{document}$$U = U_e^{\dagger } \, U_{\nu }$$\end{document}, where Ue\documentclass[12pt]{minimal}
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\begin{document}$$U_e$$\end{document} and Uν\documentclass[12pt]{minimal}
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\begin{document}$$U_{\nu }$$\end{document} are 3×3\documentclass[12pt]{minimal}
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\begin{document}$$3\times 3$$\end{document} unitary matrices which arise from the diagonalisation, respectively, of the charged lepton and the neutrino mass matrices. We consider forms of Ue\documentclass[12pt]{minimal}
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\begin{document}$$U_e$$\end{document} and Uν\documentclass[12pt]{minimal}
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\begin{document}$$U_{\nu }$$\end{document} allowing us to express δ\documentclass[12pt]{minimal}
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\begin{document}$$\delta $$\end{document} as a function of three neutrino mixing angles, present in U, and the angles contained in Uν\documentclass[12pt]{minimal}
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\begin{document}$$U_{\nu }$$\end{document}. We consider several forms of Uν\documentclass[12pt]{minimal}
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\begin{document}$$U_{\nu }$$\end{document} determined by, or associated with, symmetries, tri-bimaximal, bimaximal, etc., for which the angles in Uν\documentclass[12pt]{minimal}
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\begin{document}$$U_{\nu }$$\end{document} are fixed. For each of these forms and forms of Ue\documentclass[12pt]{minimal}
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\begin{document}$$U_e$$\end{document} allowing one to reproduce the measured values of the neutrino mixing angles, we construct the likelihood function for cosδ\documentclass[12pt]{minimal}
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\begin{document}$$\cos \delta $$\end{document}, using (i) the latest results of the global fit analysis of neutrino oscillation data, and (ii) the prospective sensitivities on the neutrino mixing angles. Our results, in particular, confirm the conclusion, reached in earlier similar studies, that the measurement of the Dirac phase in the neutrino mixing matrix, together with an improvement of the precision on the mixing angles, can provide unique information as regards the possible existence of symmetry in the lepton sector.
