Observation of B+→¯¯¯¯K0K+ and B0→K0¯¯¯¯K0

Abstract

We report observations of the b → d penguin-dominated decays B + → ¯¯¯¯ K 0 K + and B 0 → K 0 ¯¯¯¯ K 0 in 316 fb − 1 of e + e − collision data collected with the BABAR detector. We measure the branching fractions B ( B + → ¯¯¯¯ K 0 K + ) = ( 1.61 ± 0.44 ± 0.09 ) × 10 − 6 and B ( B 0 → K 0 ¯¯¯¯ K 0 ) = ( 1.08 ± 0.28 ± 0.11 ) × 10 − 6 and the C P -violating charge asymmetry A C P ( ¯¯¯¯ K 0 K + ) = 0.10 ± 0.26 ± 0.03 . Using a vertexing technique previously employed in several analyses of all-neutral final states containing kaons, we report the first measurement of time-dependent C P -violating asymmetries in B 0 → K 0 S K 0 S , obtaining S = − 1.28 + 0.80 + 0.11 − 0.73 − 0.16 and C = − 0.40 ± 0.41 ± 0.06 . We also report improved measurements of the branching fraction B ( B + → K 0 π + ) = ( 23.9 ± 1.1 ± 1.0 ) × 10 − 6 and C P -violating charge asymmetry A C P ( K 0 π + ) = − 0.029 ± 0.039 ± 0.010 .