Branching ratio and CP asymmetry of B→πη(′) decays in the perturbative QCD approach

We calculate the branching ratios and CP-violating asymmetries for B-0 -> pi(0)eta((')) and B+ -> pi(+)eta((')) decays in the perturbative QCD (pQCD) factorization approach here. We not only calculate the usual factorizable contributions, but also evaluate the non-factorizable and annihilation type contributions. Besides the current-current operators, the contributions from the QCD and electroweak penguin operators are also taken into account. The pQCD results for the CP-averaged branching ratios are Br(B+ -> pi(+) eta) approximate to 4.1 x 10(-6), Br(B+ -> pi(+)eta') approximate to 2.4 x 10(-6), and Br(B-0 -> pi(0)eta(('))) approximate to 0.2 x 10(-6), which agree very well with the measured values or currently available experimental upper limits. We also predict large CP-violating asymmetries in these decays: A(CP)(dir) (pi (+/-) eta(('))) similar to A(CP)(dir) (pi(0)eta(('))) similar to -0.35, and A(CP)(mix)(pi(0)eta(('))) similar to 0.67, but with large errors. The pQCD prediction for A(CP)(dir) (pi (+/-) eta) (A(CP)(dir) (pi (+/-) eta')) has the same (opposite) sign with the pri mary measured values. Further improvements in both theory and experiments are needed to clarify this discrepancy. (c) 2006 Elsevier B.V. All rights reserved.