QCD Approach to B->D πDecays and CP Violation

Abstract

The branching ratios and CP violations of the $B\to Dπ$ decays, including both the color-allowed and the color-suppressed modes, are investigated in detail within QCD framework by considering all diagrams which lead to three effective currents of two quarks. An intrinsic mass scale as a dynamical gluon mass is introduced to treat the infrared divergence caused by the soft collinear approximation in the endpoint regions, and the Cutkosky rule is adopted to deal with a physical-region singularity of the on mass-shell quark propagators. When the dynamical gluon mass $μ_g$ is regarded as a universal scale, it is extracted to be around $μ_g = 440$ MeV from one of the well-measured $B\to Dπ$ decay modes. The resulting predictions for all branching ratios are in agreement with the current experimental measurements. As these decays have no penguin contributions, there are no direct $CP$ asymmetries. Due to interference between the Cabibbo-suppressed and the Cabibbo-favored amplitudes, mixing-induced CP violations are predicted in the $B\to D^{\pm}π^{\mp}$ decays to be consistent with the experimental data at 1-$σ$ level. More precise measurements will be helpful to extract weak angle $2β+γ$.