Novel insights into the γγ ∗→π 0 transition form factor

Abstract

BaBar’s observation of significant deviations of the pion transition form factor (TFF) from the asymptotic expectation with Q 2>9 GeV2 has brought about a serious crisis to the fundamental picture established for such a simple $q\bar{q}$ system by perturbative QCD, i.e. the dominance of collinear factorization at high momentum transfers for the pion TFF. We show that non-factorizable contributions due to open flavors in γγ ∗→π 0 could be an important source that contaminates the pQCD asymptotic limit and causes such deviations with Q 2>9 GeV2. Within an effective Lagrangian approach, the non-factorizable amplitudes can be related to intermediate hadron loops, i.e. K (∗) and D (∗) etc., and their corrections to the π 0 and η TFFs can be estimated.