We have searched for the decay K+ → π+νν̄ in the kinematic region with pion momentum below the K+ → π+π0 peak. One event was observed, consistent with the background estimate of 0.73 ± 0.18. This implies an upper limit on B(K+ → π+ νν̄ < 4.2 × 10-9 (90% C.L.), consistent with the recently measured branching ratio of (1.57+-0.82+1.75) × 10-10, obtained using the standard model spectrum and the kinematic region above the K+ → π+π0 peak. The same data were used to search for K+ → π+X0, where X0 is a weakly interacting neutral particle or system of particles with 150 < MX0 < 250 MeV/c2.
|ジャーナル||Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics|
|出版物ステータス||Published - 2002 6 20|
ASJC Scopus subject areas
- Nuclear and High Energy Physics