Recent Results from the K2K (KEK-to-Kamioka) Neutrino Oscillation Experiment

TL;DR

The K2K neutrino oscillation experiment reports fewer observed events than expected, providing evidence for neutrino oscillations based on data collected over a year, with 27 events observed against an expectation of about 40.

Contribution

This paper presents the latest experimental results from the K2K project, offering new evidence for neutrino oscillations using accelerator-produced neutrinos.

Findings

27 fully-contained events observed in Super-Kamiokande

Expected events under null hypothesis: 40.3

Significant deficit supports neutrino oscillation evidence

Abstract

The latest results of the K2K experiment are reported. The results are based on data taken from June, 1999, to June, 2000, corresponding to a total $2.6 \cdot 10^{19}$ protons on target. Twenty seven fully-contained events in the 22.5 kton fiducial volume of Super-Kamiokande (SK) are observed. The expected number of events is estimated to be 40.3^{+4.7}_{-4.6} assuming the null oscillations hypothesis.