Implication on the pion distribution amplitude from the pion-photon transition form factor with the new BABAR data

The new BABAR data on the pion-photon transition form factor arouses people's interest for the determination of the pion distribution amplitude. To explain the data, we take both the leading valence quark state's and the nonvalence quark state's contributions into consideration, where the valence quark part up to next-to-leading order is presented and the nonvalence quark part is estimated by a phenomenological model based on its limiting behavior at both Q(2) -> 0 and Q(2) -> infinity. Our results show that to be consistent with the new BABAR data at the large Q(2) region, a broader amplitude other than the asymptoticlike pion distribution amplitude should be adopted. The broadness of the pion distribution amplitude is controlled by a parameter B. It has been found that the new BABAR data at low and high energy regions can be explained simultaneously by setting B to be around 0.60, in which the pion distribution amplitude is closed to the Chernyak-Zhitnitsky form.