Gluonic contribution to $B\to η^{(\prime)}$ form factors

Charng, Yeo-Yie; Kurimoto, T.; Li, Hsiang-nan

Gluonic contribution to $B\to η^{(\prime)}$ form factors

Authors

Charng, Yeo-Yie

Kurimoto, T.

Li, Hsiang-nan

Description

We calculate the flavor-singlet contribution to the $B\toη^{(\prime)}$ transition form factors from the gluonic content of the $η^{(\prime)}$ meson in the large-recoil region using the perturbative QCD approach. The formulation for the $η$-$η'$ mixing in the quark-flavor and singlet-octet schemes is compared, and employed to determine the chiral enhancement scales associated with the two-parton twist-3 $η^{(\prime)}$ meson distribution amplitudes. It is found that the gluonic contribution is negligible in the $B\toη$ form factors, and reaches few percents in the $B\toη'$ ones. Its impact on the accommodation of the measured $B\toη^{(\prime)} K$ branching ratios in the perturbative QCD and QCD-improved factorization approaches is elaborated.
13 pages, 9 figures, a missing overall coefficient was included into the gluonic contribution. The numerical results were revised accordingly