New measurement of the K+-->pi+ nunu branching ratio

Phys Rev Lett. 2008 Nov 7;101(19):191802. doi: 10.1103/PhysRevLett.101.191802. Epub 2008 Nov 7.

Abstract

Three events for the decay K+-->pi+ nunu have been observed in the pion momentum region below the K+-->pi+pi0 peak, 140 < Ppi < 199 MeV/c, with an estimated background of 0.93+/-0.17(stat.) -0.24+0.32(syst.) events. Combining this observation with previously reported results yields a branching ratio of B(K+-->pi+ nunu) = (1.73(-1.05)+1.15) x 10(-10) consistent with the standard model prediction.