Precise measurements of the K-s -> gamma gamma and K-L -> gamma gamma decay rates

摘要

The K-S --> gammagamma decay rate has been measured with the NA48 detector using a high intensity short neutral beam from the CERN SPS. The measured branching ratio BR(K-S gammagamma) = (2.78 +/- 0.06(stat) +/- 0.04(syst)) x 10(-6), obtained from 7461 +/- 172 K-S --> gammagamma events, is significantly higher than the O(p(4)) prediction of chiral perturbation theory. Using a K-L beam the ratio Gamma(K-L-->gammagamma)/Gamma(K-L-->pi(0)pi(0)pi(0)) = (2.81 +/- 0.01(stat) +/- 0.02(syst)) x 10(-3) has been measured. (C) 2002 Elsevier Science B.V All rights reserved. [References: 16]