Current status of K2K long-baseline neutrino-oscillation experiment

TL;DR

The K2K experiment investigates neutrino oscillations by comparing expected and observed neutrino events over a long baseline, providing early data on neutrino behavior with ongoing analysis.

Contribution

This paper reports the initial status and early results of the K2K long-baseline neutrino-oscillation experiment, including data collection and preliminary findings.

Findings

3 neutrino events observed vs. 12.3 expected

Data collected corresponds to 7% of the goal

Analysis of oscillation signals is ongoing

Abstract

The K2K (KEK to Kamioka) long-baseline neutrino-oscillation experiment was successfully started in early 1999. A total intensity of 7.20 x 10^18 protons on target, which is about 7% of the goal of the experiment, was accumulated in 39.4 days of data-taking in 1999. We obtained 3 neutrino events in the fiducial volume of the Super-Kamiokande detector, whereas the expectation based on observations in the front detectors is 12.3 +1.7/-1.9. An analysis of oscillation searches from the view points of absolute event numbers, distortion of neutrino energy spectrum, and nu_e/nu_mu ratio is in progress.