Measurement of the K{sup +}{yields}{pi}{sup +}{nu}{nu} branching ratio

Experiment E949 at Brookhaven National Laboratory studied the rare decay K{sup +}{yields}{pi}{sup +}{nu}{nu} and other processes with an exposure of 1.77x10{sup 12} K{sup +}'s. The data were analyzed using a blind analysis technique yielding one candidate event with an estimated background of 0.30{+-}0.03 events. Combining this result with the observation of two candidate events by the predecessor experiment E787 gave the branching ratio B(K{sup +}{yields}{pi}{sup +}{nu}{nu})=(1.47{sub -0.89}{sup +1.30})x10{sup -10}, consistent with the standard model prediction of (0.74{+-}0.20)x10{sup -10}. This is a more detailed report of results previously published [V. V. Anisimovsky et al., Phys. Rev. Lett. 93, 031801 (2004)].