COMPARISON OF THE K(+) AND K(-) DECAY RATES INTO THE TAU AND K-MU2 MODES.
PRINCETON UNIV N J ELEMENTARY PARTICLES LAB
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In an experiment at the Brookhaven AGS the decay rates of charged K mesons into the tau mode K to 2pi pi-, K- to 2pi- pi were measured in order to test the equality of the tau and tau- rates. A difference between these rates would constitute a violation of CP invariance. At the same time the K and K- decay rates into the K-mu2 mode K to mu muon-neutrino, K- to mu- muon-nutrino were also compared, as a test of CPT invariance. The K mesons, identified with a Cerenkov counter, were allowed to decay in flight over a well-defined region at the end of which were detectors for the charged secondaries. To detect the tau decays an array of eight triangular scintillation counters arranged in an octagon was used, with the requirement that all three pions give a count. A second bank of counters placed behind an iron absorber detected the muons from K-mu2 decays. The result for the ratio of tau and tau- decay rates is GammaGamma--tau -1 -0.0004 0.0021 or -0.0021, consistent with CP invariance. The absolute tau decay rate is Gamma-tau 4.496 plus or minus 0.030 x 1000000sec. For K-mu2 decay the result of the rate comparison is GammaGamma--mu2 -1 0.0054 plus or minus 0.0041, in agreement with zero, as predicted by CPT invariance. Author
- Nuclear Physics and Elementary Particle Physics