We review the status of $CPT$ violation in the neutrino sector. Apart from LSND, current data favors three flavors of light stable neutrinos and antineutrinos, with both halves of the spectrum having one smaller mass splitting and one larger mass splitting. Oscillation data for the smaller splitting are consistent with $CPT$. For the larger splitting, current data favor an antineutrino mass-squared splitting that is an order of magnitude larger than the corresponding neutrino splitting, with the corresponding mixing angle less than maximal. This $CPT$-violating spectrum is driven by recent results from MINOS, but is consistent with other experiments if we ignore LSND. We describe an analysis technique which, together with MINOS running optimized for muon antineutrinos, should be able to conclusively confirm the $CPT$-violating spectrum proposed here, with as little as 3 times the current data set. If confirmed, the $CPT$-violating neutrino mass-squared difference would be an order of magnitude less than the current most-stringent upper bound on $CPT$ violation for quarks and charged leptons.

• Received 28 October 2009

DOI:https://doi.org/10.1103/PhysRevD.80.113008