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Leptonic CP Violation Search and the Ambiguity of dm^2_31

Masafumi Koike·Naotoshi Okamura·Masako Saito·Tatsu Takeuchi
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Abstract

We consider a search for the CP-violating angle deltaCP in long baseline neutrino oscillation experiments. We show that the subleading deltaCP-dependent terms in the nu_mu -> nu_e oscillation probability can be easily obscured by the ambiguity of the leading term which depends on |dm^2_31|. It is thus necessary to determine the value of dm^2_31 with a sufficient accuracy. The nu_mu survival events, which can be accumulated simultaneously with the nu_e appearance events, can serve for this purpose owing to its large statistics. Therefore, the combined analysis of nu_e appearance and nu_mu survival events is crucial to provide a restrictive constraint on deltaCP. Taking a test experimental setup, we demonstrate in the deltaCP-dm^2_31 plane that the analysis of nu_e appearance events leads to less restrictive constraints on the value of deltaCP due to the ambiguity of dm^2_31 and that the combined analysis efficiently improves the constraints.

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Masafumi Koike, Naotoshi Okamura, Masako Saito, Tatsu Takeuchi. 2006-03-22. Leptonic CP Violation Search and the Ambiguity of dm^2_31. https://doi.org/10.1103/physrevd.73.053010

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