Evidence for muon neutrino oscillation in an accelerator-based experiment

Area of Science:

• Particle Physics
• Neutrino Physics
• Astroparticle Physics

Background:

• Neutrino oscillation is a quantum mechanical phenomenon where neutrinos change between different "flavors" or types.
• Understanding neutrino oscillations is crucial for particle physics and cosmology, impacting the Standard Model.
• The KEK to Kamioka (K2K) experiment was designed to investigate neutrino oscillations using an accelerator-generated neutrino beam.

Purpose of the Study:

• To present results on muon neutrino (nu(mu)) oscillation.
• To provide evidence for neutrino oscillations using a long-baseline experiment.

Main Methods:

• Utilized an accelerator-produced nu(mu) beam with a mean energy of 1.3 GeV.
• Directed the neutrino beam from KEK to the Super-Kamiokande detector, a distance of 250 km.
• Analyzed the energy-dependent disappearance of nu(mu) in the detector.

Main Results:

• Observed a statistically significant energy-dependent disappearance of muon neutrinos.
• The observed disappearance is consistent with nu(mu) oscillating into tau neutrinos (nu(tau)).
• The probability of observing these results without neutrino oscillation is 0.0050% (4.0 sigma).

Conclusions:

• The K2K results provide strong evidence for neutrino oscillation.
• The data supports the hypothesis that muon neutrinos oscillate into tau neutrinos.
• This experiment contributes significantly to the understanding of neutrino properties and fundamental physics.