A class of extensions of the Standard Model allows Lorentz and $CPT$ violations, which can be identified by the observation of sidereal modulations in the neutrino interaction rate. A search for such modulations was performed using the T2K on-axis near detector. Two complementary methods were used in this study, both of which resulted in no evidence of a signal. Limits on associated Lorentz and $CPT$-violating terms from the Standard Model extension have been derived by taking into account their correlations in this model for the first time. These results imply such symmetry violations are suppressed by a factor of more than $10^{20}$ at the GeV scale.

• Received 7 March 2017

DOI:https://doi.org/10.1103/PhysRevD.95.111101

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Published by the American Physical Society