Regular Article - Theoretical Physics
Novel insights into the γγ ∗→π 0 transition form factor
Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, P.R. China
2 Theoretical Physics Center for Science Facilities, CAS, Beijing, 100049, China
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Published online: 11 April 2012
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 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.
© Springer-Verlag / Società Italiana di Fisica, 2012