Abstract
In the first year of physics run, the E949 experiment at Brookhaven National Laboratory has already collected
1.8×
10
12
kaons stopping in the target. Additional evidence for the rare charged kaon decay
K
+
→
π
+
ν
ν
¯
has been observed. Combined with previous results from the E787 experiment, the branching ratio is measured to be Br(
K
+
→
π
+
ν
ν
¯
)=
(
1.47
+1.30
−0.89
)×
10
−10
.