Measurement of theKSbranching ratio into two pions

Abstract

A spark-chamber experiment to measure the branching ratio of the short-lived K , meson into the modes x ' x and ?roxo was performed at the Princeton-Pennsylvania Accelerator. A 1.0-GeV/c beam of incident x mesons produced A°Ko from a polyethylene target. The decay of A into ?r p was used as a signal for the associated production of a KO. A total of 160000 pictures, taken in two views, were completely scanned for V's (charged decays of neutral particles), and all tracks were measured. A final sample of 16000 K , charged decays and 65 000 A* charged decays directly determined the branching fraction for K , to decay into x + x -to be 0.684 + 0.009. The branching ratio found by this experiment is then r(K, -+ n'n-)/r(K, -+ non0) = 2.169 + 0.094.