New Measurement of the ${K}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}\ensuremath{\nu}\overline{\ensuremath{\nu}}$ Branching Ratio

New Measurement of the $K^{+} \to π^{+} ν \bar{ν}$ Branching Ratio

A. V. Artamonov et al. (E949 Collaboration)

Phys. Rev. Lett. 101, 191802 – Published 7 November 2008

Abstract

Three events for the decay $K^{+} \to π^{+} ν \bar{ν}$ have been observed in the pion momentum region below the $K^{+} \to π^{+} π^{0}$ peak, $140 < P_{π} < 199 MeV / c$ , with an estimated background of $0.93 \pm 0.17 (stat .)_{- 0.24}^{+ 0.32} (syst .)$ events. Combining this observation with previously reported results yields a branching ratio of $B (K^{+} \to π^{+} ν \bar{ν}) = ({1.73}_{- 1.05}^{+ 1.15}) \times 10^{- 10}$ consistent with the standard model prediction.