Results from the K2K Long--Baseline Neutrino Oscillation Experiment

Abstract

The K2K Long--Baseline neutrino oscillation experiment has been aquiring data since mid-1999 and has analysed those up to March of 2001. Forty-four fully contained events are observedin the fiducial volume of the far detector where $64^{+6.1}_{-6.6}$ are expected based partly on measurements near the beam production point. There is virtually no background for the contained event search. The methods established in this experiment are crucial for operation of future similar experiments to probe the nature of mixing in the neutral lepton sector, a necessary step in understanding the nature of family structure and of mass itself. A brief history and a few notes about the future and direction of the field precede the description of the experiment and its results.