paper

Branching Ratio and CP Asymmetry of Decays in the Perturbative QCD Approach

arXiv:hep-ph/0511161 · doi:10.1016/j.nuclphysb.2006.01.021

Abstract

We calculate the branching ratios and CP-violating asymmetries for and 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 , , and , 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}(π^\pm \etap)\sim A_{CP}^{dir}(π^0 \etap)\sim -0.35 $, and $A_{CP}^{mix}(π^0 \etap)\sim 0.67$, but with large errors. The pQCD prediction for ( has the same (opposite) sign with the primary measured values. Further improvements in both theory and experiments are needed to clarify this discrepancy.

28 pages, 8 figures, several typos corrected

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