The Photon–Pion Transition Form Factor: Incompatible Data or Incompatible Models?

• Published in: Few-body systems Vol. 55; no. 5-7; pp. 373 - 379
• Main Authors: de Melo, J. P. B. C., El-Bennich, Bruno, Frederico, Tobias
• Format: Journal Article
• Language: English
• Published: Vienna Springer Vienna 01.06.2014; Springer Nature B.V
• Subjects: Amplitudes; Atomic; Charge; Constants; Form factors; Hadrons; Heavy Ions; Mathematical models; Molecular; Nuclear Physics; Optical and Plasma Physics; Particle and Nuclear Physics; Physics; Physics and Astronomy; Pions; Quantum field theory; Quark models; Wave functions; Form Factor; Transition Form Factor; Charge Radius; Light Front; BaBar Data
• ISSN: 0177-7963; 1432-5411
• DOI: 10.1007/s00601-014-0853-z

The elastic and γ → π transition form factors of the pion along with its usual static observables are calculated within a light-front field approach to the constituent quark model. The focus of this exercise in a simple model is on a unified description of all observables with one singly parametrized light-front wave function to detect possible discrepancies in experimental data, in particular the contentious large momentum-squared data on the transition factor as reported by BaBar and Belle. We also discuss the relation of a small to vanishing pion charge radius with an almost constant pion distribution amplitude and compare our results with those obtained in a holographic light-front model.