MINOS and CPT-violating neutrinos

TL;DR

This paper reviews evidence for CPT violation in neutrino oscillations, highlighting recent MINOS results suggesting a possible difference in neutrino and antineutrino mass splittings, and proposes an analysis method to confirm this.

Contribution

It introduces an analysis technique optimized for muon antineutrinos to conclusively test CPT violation in neutrino mass spectra with additional data.

Findings

MINOS results suggest larger antineutrino mass splitting

Current data compatible with CPT for small splittings

Proposed method could confirm CPT violation with threefold data increase

Abstract

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 is 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 three 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.