Abelian anomaly and neutral pion production

Abstract

We show that in fully-self-consistent treatments of the pion; namely, its static properties and elastic and transition form factors, the asymptotic limit of the product Q^2 G_{γ* γπ^0}(Q^2), determined a priori by the interaction employed, is not exceeded at any finite value of spacelike momentum transfer. Furthermore, in such a treatment of a vector-vector contact-interaction one obtains a γ* γ-> π^0 transition form factor that disagrees markedly with all available data. We explain that the contact interaction produces a pion distribution amplitude which is flat and nonvanishing at the endpoints. This amplitude characterises a pointlike pion bound-state. Such a state has the hardest possible form factors; i.e., form factors which become constant at large momentum transfers and hence are in striking disagreement with completed experiments. On the other hand, interactions with QCD-like behaviour produce soft pions, a valence-quark distribution amplitude that vanishes as ~(1-x)^2 for x~1, and results that agree with the bulk of existing data. Our analysis supports a view that the large-Q^2 data obtained by the BaBar Collaboration is not an accurate measure of the γ* γ-> π^0 form factor.

11 pages, 6 figures

References in corpus (40)

• Dyson-Schwinger Equations and the Application to Hadronic Physics
• Dyson-Schwinger Equations: Density, Temperature and Continuum Strong QCD
• Dyson-Schwinger equations: a tool for hadron physics
• pi- and K-meson Bethe-Salpeter Amplitudes
• Measurements of the Meson-Photon Transition Form Factors of Light Pseudoscalar Mesons at Large Momentum Transfer
• Infrared Properties of QCD from Dyson-Schwinger equations
• Pion mass and decay constant
• Goldstone Theorem and Diquark Confinement Beyond Rainbow-Ladder Approximation
• Measurement of the gamma gamma* --> pi0 transition form factor
• Sketching the Bethe-Salpeter kernel
• Dynamical Chiral Symmetry Breaking, Goldstone's Theorem and the Consistency of the Schwinger--Dyson and Bethe--Salpeter Equations
• The $\pi$, $K^{+}$, and $K^0$ electromagnetic form factors
• Unquenched quark propagator in Landau gauge
• Hadron Properties and Dyson-Schwinger Equations
• Distribution Functions of the Nucleon and Pion in the Valence Region
• Analysis of a quenched lattice-QCD dressed-quark propagator
• Extended NJL Model for light and heavy mesons without q-qbar thresholds
• The Quark-Photon Vertex and the Pion Charge Radius
• Aspects and consequences of a dressed-quark-gluon vertex
• Unquenched Gluon Propagator in Landau Gauge
• Aspects of Hadron Physics
• Electromagnetic Pion Form Factor and Neutral Pion Decay Width
• Essence of the vacuum quark condensate
• Valence-quark distributions in the pion
• Shape of Pion Distribution Amplitude
• Pion form factor from a contact interaction
• Electromagnetic properties of ground and excited state pseudoscalar mesons
• On the Pion Distribution Amplitude Shape
• Pseudovector components of the pion, pi^0 -> gamma gamma, and F_pi(q^2)
• Electromagnetic Transition Form Factors of Light Mesons
• On the massive gluon propagator, the PT-BFM scheme and the low-momentum behaviour of decoupling and scaling DSE solutions
• Analysis of full-QCD and quenched-QCD lattice propagators
• Measurement of the eta and etaprime transition form factors at q^2=112 GeV^2
• Pion Loop Contribution to the Electromagnetic Pion Charge Radius
• Flavour symmetry breaking and meson masses
• Calculation of the anomalous $\gamma {\pi }^{\ast }\to \pi \pi$ form factor
• Pion transition form factor at the two-loop level vis-à-vis experimental data
• Theory Support for the Excited Baryon Program at the Jlab 12 GeV Upgrade
• gamma^* gamma -> pi^0 transition and asymptotics of gamma^* gamma and gamma^* gamma^* transitions of other unflavored pseudoscalar mesons
• Anomalous gamma -> 3 pi amplitude in a bound-state approach

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