Nonfactorizable contributions to $B\to D^{(\ast )}M$ decays

Abstract

While the factorization assumption works well for many two-body nonleptonic $B$ meson decay modes, the recent measurement of $\bar{B}\to D^{(\ast )0}{M}^0$ with $M=\pi$, $\rho$ and $\omega$ shows large deviation from this assumption. We analyze the $B\to D^{(\ast )}M$ decays in the perturbative QCD approach based on $k_T$ factorization theorem, in which both factorizable and nonfactorizable contributions can be calculated in the same framework. Our predictions for the Bauer-Stech-Wirbel parameters, $|a_2/a_1|=0.43\pm 0.04$ and $Arg(a_2/a_1)\sim -42^{\circ }$ and $|a_2/a_1|=0.47\pm 0.05$ and $Arg(a_2/a_1)\sim -41^{\circ }$, are consistent with the observed $B\to D\pi$ and $B\to D^{\ast }\pi$ branching ratios, respectively. It is found that the large magnitude $|a_2|$ and the large relative phase between $a_2$ and $a_1$ come from color-suppressed nonfactorizable amplitudes. Our predictions for the ${\bar{B}}^0\to D^{(\ast )0}{\rho }^0$, $D^{(\ast )0}\omega$ branching ratios can be confronted with future experimental data.

25 pages with Latex, axodraw.sty, 6 figures and 5 tables, Version published in PRD, Added new section 5 and references