Further Evidence for the Decay K+ to pi+ neutrino-antineutrino

TL;DR

This paper presents additional experimental evidence for the rare decay of a kaon into a pion and a neutrino-antineutrino pair, with new data supporting previous findings and estimating the decay's branching ratio.

Contribution

It provides new experimental data confirming the decay K+ to pi+ neutrino-antineutrino and refines the branching ratio estimate based on combined data sets.

Findings

Observed a total of two decay events in the specified momentum range.

Estimated background contribution of 0.15 ± 0.05 events.

Calculated branching ratio B=1.57^{+1.75}_{-0.82} × 10^{-10}.

Abstract

Additional evidence for the rare kaon decay K+ to pi+ neutrino-antineutrino has been found in a new data set with comparable sensitivity to the previously reported result. One new event was observed in the pion momentum region examined, 211<P<229 MeV/c, bringing the total for the combined data set to two. Including all data taken, the backgrounds were estimated to contribute 0.15 pm 0.05 events. The branching ratio is B=1.57^{+1.75}_{-0.82} 10^{-10}.