What can we learn from $B\to a_1(1260)(b_1(1235))\pi(K)$ decays?

Understand

We investigate the $B\to a_1(1260)(b_1(1235))\pi(K)$ 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 with the large decay rates of $B^-\to a_1^0\pi^-$ and $B^-\to a_1^-\pi^0$.
• For $\bar B^0\to (a_1^+, b_1^+)K^-$ decays which are both induced by $b\to s$ transition, theoretical predictions on their decay rates are larger than the data by a factor of 2.8 and 5.5, respectively.
• Large electro-weak penguins or some new mechanism are expected to explain the branching ratios of $B^-\to b_1^0K^-$ and $B^-\to a_1^-\bar K^0$.