What can we learn fromB→a1(1260)(b1(1235))π(K)decays?

Abstract

We investigate the $B\ensuremath{\rightarrow}{a}_{1}(1260)({b}_{1}(1235))\ensuremath{\pi}(K)$ decays under the factorization scheme and find many discrepancies between theoretical predictions and the experimental data. In the tree-dominated processes, large contributions from color-suppressed tree diagrams are required in order to accommodate the large decay rates of ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}{a}_{1}^{0}{\ensuremath{\pi}}^{\ensuremath{-}}$ and ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}{a}_{1}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}$. For ${\overline{B}}^{0}\ensuremath{\rightarrow}({a}_{1}^{+},{b}_{1}^{+}){K}^{\ensuremath{-}}$ decays which are induced by $b\ensuremath{\rightarrow}s$ transition, theoretical predictions on their decay rates are larger than the data by a factor of 2.8 and 5.5, respectively. Large electroweak penguins or some new mechanism are expected to explain the branching ratios of ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}{b}_{1}^{0}{K}^{\ensuremath{-}}$ and ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}{a}_{1}^{\ensuremath{-}}{\overline{K}}^{0}$. The soft-collinear effective theory has the potential to explain large decay rates of ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}{a}_{1}^{0}{\ensuremath{\pi}}^{\ensuremath{-}}$ and ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}{a}_{1}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}$ via a large hard-scattering form factor ${\ensuremath{\zeta}}_{J}^{B\ensuremath{\rightarrow}{a}_{1}}$. We will also show that, with proper charming penguins, predictions on the branching ratios of ${\overline{B}}^{0}\ensuremath{\rightarrow}({a}_{1}^{+},{b}_{1}^{+}){K}^{\ensuremath{-}}$ can also be consistent with the data.