Observation of the decay $K^{+}\to \ddot{I}{€}^{+}\hat{I}½\bar{\hat{I}}½$

Abstract

We have observed 1 event consistent with the signature expected of the rare decay of a positive kaon to a positive pion and a neutrino anti-neutrino pair. In the examined momentum region of 211 to 230 MeV/c in the center of mass of the kaon we estimated the backgrounds to be about $0.08\pm 0.03$ events. From this observation we estimate the branching ratio to be $4.2_{-3.5}^{+9.7}\times 10^{-10}$. In this presentation I will explain the experiment, and the analysis techniques. I will also discuss the expected improvements in the near future from the analysis of new data sets.

7 pages, 5 figure files, REVTEX, Proceedings of the Division of Particles and Fields Conference 1999, Jan 5-9, University of California, Los Angeles