Evidence forB+→K¯0K+andB0→K0K¯0, and Measurement of the Branching Fraction and Search for DirectCPViolation inB+→K0π+

The authors present evidence for the b {yields} d penguin-dominated decays B{sup +} {yields} {bar K}{sup 0}K{sup +} and B{sup 0} {yields} K{sup 0}{bar K}{sup 0} with significances of 3.5 and 4.5 standard deviations, respectively. The results are based on a sample of 227 million {Upsilon}(4S) {yields} B{bar B} decays collected with the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} collider at SLAC. We measure the branching fractions {Beta}(B{sup +} {yields} {bar K}{sup 0}K{sup +}) = (1.5 {+-} 0.5 {+-} 0.1) x 10{sup -6} (< 2.4 x 10{sup -6}) and {Beta}(B{sup 0} {yields} K{sup 0}{bar K}{sup 0}) = (1.19{sub -0.35}{sup +0.40} {+-} 0.13) x 10{sup -6}, where the uncertainties are statistical and systematic, respectively, and the upper limit on the branching fraction for {bar K}{sup 0}K{sup +} is at the 90% confidence level. They also present improved measurements of the charge-averaged branching fraction {Beta}(B{sup +} {yields} K{sup 0}{pi}{sup +}) = (26.0 {+-} 1.3 {+-} 1.0) x 10{sup -6} and CP-violating charge asymmetry {Alpha}{sub CP} (K{sup 0}{pi}{sup +}) = -0.09 {+-} 0.05 {+-} 0.01, where the uncertainties are statistical and systematic, respectively.