[Paper Review] Status of CPT-violating neutrinos

Gabriela Barenboim, Joseph Lykken|arXiv (Cornell University)|Aug 21, 2009

Particle physics theoretical and experimental studies4 citations

TL;DR

The paper proposes a CPT-violating neutrino mass spectrum where the antineutrino mass-squared splitting is an order of magnitude larger than the neutrino splitting, with a non-maximal mixing angle. Based on MINOS data and a proposed optimized analysis, this spectrum could be confirmed with three times the current data, offering the first potential evidence of CPT violation in neutrinos, with a predicted mass-squared difference an order of magnitude below current quark and charged lepton bounds.

ABSTRACT

Abstract: We review the status of CP T 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 CP T. 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 lessthan-maximal. This CP T-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 CP T-violating spectrum proposed here, with as little as three times the current data set. If confirmed, the CP T-violating neutrino mass-squared difference would be an order of magnitude less than the current most-stringent upper bound on CP T violation for quarks and charged leptons.

Motivation & Objective

• To assess the viability of CPT-violating neutrino mass spectra using current oscillation data.
• To identify experimental conditions under which CPT violation in neutrinos could be conclusively confirmed.
• To reconcile recent MINOS results with other experiments, excluding LSND, under a CPT-violating framework.
• To propose a data analysis technique that enhances sensitivity to CPT violation in the neutrino sector.

Proposed method

• Analyzing oscillation data from neutrino and antineutrino experiments, particularly focusing on the muon neutrino and antineutrino sector.
• Applying a modified analysis technique sensitive to differences in mass-squared splittings between neutrinos and antineutrinos.
• Optimizing MINOS data collection for muon antineutrino events to enhance sensitivity to CPT-violating effects.
• Using statistical modeling to project confirmation of the CPT-violating spectrum with three times the current data set.
• Comparing predicted CPT-violating mass-squared differences with existing experimental bounds on CPT violation in quarks and charged leptons.

Experimental results

Research questions

• RQ1 Is there evidence for a CPT-violating neutrino mass spectrum in current oscillation data?
• RQ2 Can the discrepancy between neutrino and antineutrino mass-squared splittings be confirmed with existing data?
• RQ3 What data collection strategy would maximize sensitivity to CPT violation in the neutrino sector?
• RQ4 How does the proposed CPT-violating spectrum compare to the most stringent bounds on CPT violation in other fermion sectors?
• RQ5 Can the CPT-violating spectrum be conclusively confirmed with a modest increase in data volume?

Key findings

• Current data, excluding LSND, favor a CPT-violating neutrino spectrum with an antineutrino mass-squared splitting approximately an order of magnitude larger than the neutrino splitting.
• The oscillation data for the smaller mass splitting are consistent with CPT invariance.
• The larger mass splitting exhibits a non-maximal mixing angle, supporting the CPT-violating scenario.
• MINOS data provide the primary evidence for this CPT-violating spectrum, particularly through its sensitivity to muon antineutrino events.
• With three times the current data set and optimized analysis, the CPT-violating spectrum could be conclusively confirmed.
• If confirmed, the predicted CPT-violating mass-squared difference would be an order of magnitude smaller than the current most stringent upper bound on CPT violation for quarks and charged leptons.