Search for active neutrino disappearance using neutral-current interactions in the MINOS long-baseline experiment

Area of Science:

• Particle Physics
• Neutrino Physics
• Astroparticle Physics

Background:

• Neutrino oscillations are a key phenomenon in particle physics.
• The existence of sterile neutrinos is hypothesized but not experimentally confirmed.
• Detecting oscillations of muon neutrinos (nu(mu)) into sterile neutrinos would provide evidence for physics beyond the Standard Model.

Purpose of the Study:

• To conduct the first detailed comparison of neutral-current neutrino interaction rates and spectra at two geographically separated locations.
• To search for evidence of muon neutrino oscillations into sterile neutrinos by looking for a depletion in interaction rates at the farther detector.
• To constrain the oscillation parameters, specifically the fraction of muon neutrinos mixing with sterile neutrinos.

Main Methods:

• Utilized two widely separated detector sites to compare neutrino interaction event rates and reconstructed energy spectra.
• Analyzed both neutral-current and charged-current neutrino interaction data.
• Performed a fit to the observed energy spectra assuming single mass-squared splitting for neutrino oscillations.

Main Results:

• No anomalous depletion in the reconstructed energy spectrum was observed at the far site.
• A fit to the data yielded a limit on the fraction of muon neutrinos oscillating to a sterile neutrino, finding it to be below 0.68 at a 90% confidence level.
• A less stringent limit was also presented, considering potential contributions from electron neutrino (nu(e)) appearance.

Conclusions:

• The study found no evidence supporting the oscillation of muon neutrinos into sterile neutrinos within the analyzed data.
• The results place stringent limits on the mixing fraction of muon neutrinos with sterile neutrinos.
• Further investigation may be needed to account for potential nu(e) contributions to the observed rates.