Eur. Phys. J. C (2007) 50: 771-779
https://doi.org/10.1140/epjc/s10052-007-0245-3

Regular Article - Theoretical Physics

Determination of the η and η^′ mixing angle from the pseudoscalar transition form factors

¹ Institute of High Energy Physics, Chinese Academy of Sciences, P.O. Box 918(4), Beijing, 100039, P.R. China
² Institute of Theoretical Physics, Chinese Academy of Sciences, P.O. Box 2735, Beijing, 100080, P.R. China
³ Department of Physics, Chongqing University, Chongqing, 400044, P.R. China

^* e-mail: wuxg@itp.ac.cn

Received: 1 December 2006
Published online: 13 March 2007

Abstract

The possible range of the η– mixing angle is determined from the transition form factors F_ηγ(Q²) and with the help of up-to-date experimental data. For this purpose, the quark-flavor mixing scheme is adopted and the pseudoscalar transition form factors are calculated in the framework of light-cone pQCD, in which the transverse-momentum corrections and the contributions beyond the leading Fock state have been carefully taken into consideration. We construct a phenomenological expression to estimate the contributions to the form factors beyond the leading Fock state, based on their asymptotic behavior at Q²→0 and . By taking the quark-flavor mixing scheme, our results lead to , where the first error comes from the experimental uncertainty and the second error from the uncertainties of the parameters of the wavefunction. The possible intrinsic charm component in η and is discussed, and our present analysis also disfavors a large intrinsic charm component in η and , e.g. .