Soft Nonfactorizable Contribution to \bar{B}^0 \to D^0\pi^0

Abstract

For the color-suppressed $\bar{B}^0\longrightarrow D^{0}\pi^{0}$ decay, nonfactorizable contributions are expected to be leading and naive factorization description breaks down. We estimate $1/m_b$ power-suppressed nonfactorizable effect in $\bar{B}^0\longrightarrow D^{0}\pi^{0}$, which is due to soft exchange between the emitted heavy-light quark pair and $B\pi$ system, in the framework of QCD light-cone sum rules (LCSR). The resulting correction to the decay amplitude is found to be numerically comparable with the corresponding factorizable piece, estimated at about $(50-110)%$ of the latter. The relevant parameter $a_2$ receives a positive number contribution, due to the factorizable correction and the power-suppressed soft effect. Our findings would be crucial to phenomenological understanding of the $\bar{B}^0\longrightarrow D^{0}\pi^{0}$ decay.