Shape of Pion Distribution Amplitude
Abstract
A scenario is investigated in which the leading-twist pion distribution amplitude phipi (x) is approximated by the pion decay constant fpi for all essential values of the light-cone fraction x. A model for the light-front wave function Psi(x,kperp) is proposed that produces such a distribution amplitude and has a rapidly decreasing (exponential for definiteness) dependence on the light-front energy combination kperp2/x(1-x). It is shown that this model easily reproduces the fit of recent large-Q2 BaBar data on the photon-pion transition form factor. Some aspects of scenario with flat pion distribution amplitude are discussed.
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