Study of the suppressed B meson decay B--> DK-, D -> K+pi(-)

Abstract

We report a study of the suppressed B meson decay B--> DK- followed by D -> K+pi(-), where D indicates a D-0 or (D)overbar(0) state. The two decay paths interfere and provide information on the CP-violating angle phi(3). We use a data sample containing 657x10(6) B(B)overbar pairs recorded at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) storage ring. We do not find significant evidence for the mode B--> DK-, D -> K+pi(-), and set an upper limit of r(B)< 0.19, where r(B) is the magnitude of the ratio of amplitudes vertical bar A(B-->(D)K-0(-))/A(B-->(DK-)-K-0)vertical bar. The decay B--> D pi(-), D -> K+pi(-) is also analyzed as a reference, for which we observe a signal with 6.6 sigma significance, and measure the charge asymmetry A(D pi) to be -0.02(-0.16)(+0.15)(stat)+/- 0.04(syst). In addition, the ratio B(B-->(DK-)-K-0)/B(B--> D-0 pi(-)) is measured to be [6.77 +/- 0.23(stat)+/- 0.30(syst)]x10(-2).