2010/03/24 by A. E. Dorokhov, Dorokhov, A. E.
Physics and Astronomy · #FOS: Physical sciences #High Energy Physics - Experiment (hep-ex) #High Energy Physics - Phenomenology (hep-ph) #High-Energy Particle Collisions Research #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions
paper · pdf · doi:10.48550/arxiv.1003.4693
openalex publication_date 2010/03/24 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
Recently, the BABAR collaboration published (arXiv:0905.4778) data for the photon-pion transition form factor Fπγγ∗(Q2), which are in strong contradiction to the predictions of the standard factorization approach to perturbative QCD. Immediately afterwards, two mechanisms were suggested (A.E. Dorokhov, arXiv:0905.4577; A.V. Radyushkin, arXiv:0906.0323), that logarithmically enhance the form factor asymptotics and therefore provide a qualitatively satisfactory description of the BABAR data. However, the physics of the BABAR effect was not fully clarified. In the present work, based on a nonperturbative approach to the QCD vacuum and on rather universal assumptions, we show that there exists two asymptotic regimes for the pion transition form factor. One regime with asymptotics Fπγ∗γ(Q2)∼1/Q2 corresponds to the result of the standard QCD factorization approach, while other violates the standard factorization and leads to asymptotic behavior as Fπγ∗γ(Q2)∼ln(Q2)Q2. Furthermore, considering specific nonlocal chiral quark models, we find the region of parameters, where the existing CELLO, CLEO and BABAR data for the pion transition form factor are successfully described.