Evidence for the suppressed decay B- -> DK-, D -> K+ pi(-)pi(0)

Abstract

We report a study of the suppressed decay B- -> DK-, D -> K+ pi(-) pi(0), where D denotes either a D-0 or a (D) over bar (0) meson. The decay is sensitive to the CP-violating parameter phi(3). Using a data sample of 772 x 10(6) B (B) over bar pairs collected at the Upsilon(4S) resonance with the Belle detector, we measure the ratio of branching fractions of the above suppressed decay to the favored decay B- -> DK-, D -> K- pi(+) pi(0). Our result is R-DK = [1.98 +/- 0.62 (stat) +/- 0.24 (syst)] x 10(-2), which indicates the first evidence of the signal for this suppressed decay with a significance of 3.2 standard deviations. We measure the direct CP asymmetry between the suppressed B- and B+ decays to be A(DK) = 0.41 +/- 0.30(stat) +/- 0.05(syst). We also report measurements for the analogous quantities R-D pi and A(D pi) for the decay B- -> D pi(-), D -> K+ pi(-)pi(0).