Book Description

The conserved vector current theory predicts that the branching ratio for the decay of a charged pion into a neutral pion is (1.05=0.02)x10 to the -8th power, if the coupling constant is derived from muon decay, or (1.00=0.02)x10 to the -8th power, if the coupling constant is derived from nuclear beta decay. Using spark chambers to distinguish the nearly anticollinear gamma rays from pi(+) beta decay from a background of other gamma rays, we have found 36 events and have measured the branching ratio to be (0.97=0.20)x10 to the -8th power, in agreement with the theoretical prediction and previous measurements. The method of background subtraction (approximately 10%) depends only on knowing that the background is isotropic for gamma rays having opening angles between 160 degrees and 180 degrees. (Author).