Observation of B_s~0 → K~+K~- and Measurements of Branching Fractions of Charmless Two-Body Decays of B~0 and B_s~0 Mesons in pp Collisions at s~(1/2) = 1.96 Te V

摘要

We search for decays of the type B_((s))~0 → h~+h'~-(where h,h' = K or π) in 180 pb~(-1) of pp collisions collected at the Tevatron by the upgraded Collider Detector at Fermilab. We report the first observation of the new mode B_s~0 → K~+ K~- with a yield of 236 ± 32 events, corresponding to (f_s/f_d) x B(B_s~0 → K~+K~-)/B(B~0 → K~-π~-) = 0.46 ± 0.08(stat) ± 0.07(syst), where f_s/f_d is the ratio of production fractions of B_s~0 and B~0. We find results in agreement with world averages for the B~0 modes, and set the following new limits at 90% C.L.: B(B_s~0 → K~-π~+) < 5.6 x 10~(-6) and B(B_s~0 → π~+π~-) < 1.7 x 10~(-6).