Experiment E949 at Brookhaven National Laboratory has observed three new events consistent with the decay K+→π+νν̄ in the pion momentum region 140<Pπ<199MeV/c in an exposure of 1.71×1012 stopped kaons with an estimated total background of 0.93±0.17(stat)-0. 24+0.32(syst) events. This brings the total number of observed K+→π+νν̄ events to seven. Combining this observation with previous results, assuming the pion spectrum predicted by the standard model, results in a branching ratio of B(K+→π+νν̄)=(1.73-1.05+1.15) ×10-10. An interpretation of the results for alternative models of the decay K+→π++nothing is also presented.
|Journal||Physical Review D - Particles, Fields, Gravitation and Cosmology|
|Publication status||Published - 2009 May 1|
ASJC Scopus subject areas
- Nuclear and High Energy Physics
- Physics and Astronomy (miscellaneous)