Gluonic components of the pion and the transition form factor ${\gamma }^{\ast }{\gamma }^{\ast }\to {\pi }^0$

Abstract

We propose an effective lagrangian for the coupling of the neutral pion with gluons whose strength is determined by a low energy theorem. We calculate the contribution of the gluonic components arising from this interaction to the pion transition form factor ${\gamma }^{\ast }{\gamma }^{\ast }\to {\pi }^0$ using the instanton liquid model to describe the QCD vacuum. We find that this contribution is large and might explain the anomalous behavior of the form factor at large virtuality of one of the photons, a feature which was recently discovered by the BaBar Collaboration.

arXiv comment10 pages,2 figures,final version to be published in Phys.Rev.D

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• Influence of confining gluon configurations on the $P\to {\gamma }^{\ast }\gamma$ transition form factors
• Pion-Photon Transition Form Factor and Pion Distribution Amplitude in QCD: Facing the Enigmatic Behavior of the BaBar Data
• Theoretical description and measurement of the pion-photon transition form factor
• Pion transition form factor in the Domain model of QCD vacuum