The puzzle of the π-> γγ* transition form factor

Abstract

We study the $P\to \gamma {\gamma }^{\ast }$ ($P={\pi }^0,\eta ,{\eta }^{\prime }$) transition form factors by means of the local-duality (LD) version of QCD sum rules. For the case of $\eta$ and ${\eta }^{\prime }$, the conventional LD model provides a good description of the existing data. However, for the $\pi$ form factor we find disagreement with recent BaBar results for high $Q^2$ even though the accuracy of the LD approximation is expected to increase with $Q^2$. It remains mysterious why the $\eta$ and ${\eta }^{\prime }$ form factors to virtual photons, on the one hand, and the $\pi$ form factor, on the other hand, show a qualitatively different behaviour corresponding to a rising with $Q^2$ violation of local duality in the pion case. In a quantum mechanical example we show that, for a bound-state size of about 1 fm, the LD sum rule provides an accurate prediction for the form factor for $Q^2\ge$ a few GeV${}^2$.

8 pages

References in corpus (10)

• Abelian anomaly and neutral pion production
• Light Cone Sum Rules for the pi0-gamma*-gamma Form Factor Revisited
• Decay constants of heavy pseudoscalar mesons from QCD sum rules
• Systematic uncertainties of hadron parameters obtained with QCD sum rules
• Axial anomaly as a collective effect of meson spectrum
• Can one control systematic errors of QCD sum rule predictions for bound states?
• Pion form factor at spacelike momentum transfers from local-duality QCD sum rule
• Pion elastic and $({\pi }^0,\eta ,{\eta }^{\prime })\to \gamma {\gamma }^{\ast }$ transition form factors in a broad range of momentum transfers
• Quark-hadron duality and hadron properties from correlators of pseudoscalar and axial currents
• The photon to pseudoscalar meson transition form factors

Cited by in corpus (19)

• Joint resummation for pion wave function and pion transition form factor
• Transition Form Factors and Mixing of Pseudoscalar Mesons from Anomaly Sum Rule
• Spacelike and timelike form factors for the $({\pi }^0,\eta ,{\eta }^{\prime })\to {\gamma }^{\ast }\gamma$ transitions in the light-front quark model
• Universal behaviour of the ${\gamma }^{\ast }\gamma \to ({\pi }^0,\eta ,{\eta }^{\prime })$ transition form factors
• Pion to photon transition form factors with basis light-front quantization
• On the ${\gamma }^{\ast }\gamma \to \pi (\eta ,{\eta }^{\prime })$ transition form factors
• The ${\gamma }^{\ast }{\gamma }^{\ast }\to {\eta }_c$ transition form factor
• Influence of confining gluon configurations on the $P\to {\gamma }^{\ast }\gamma$ transition form factors
• Systematic twist expansion of $({\eta }_c,{\eta }_b)\to {\gamma }^{\ast }\gamma$ transition form factors in light-front quark model
• Study of pesudoscalar transition form factors within light front quark model
• Non-factorizable charming loops in FCNC B decays vs B-decay semileptonic form factors
• Direct Searches for New Physics Particles at BABAR
• Charming-loop contribution to $B_s\to \gamma \gamma$ decay
• Local-duality QCD sum rules for strong isospin breaking in the decay constants of heavy-light mesons
• Search for new ${\pi }^0$-like particles produced in association with a $\tau$-lepton pair
• Advances in QCD sum rule calculations
• On the description of exotic hadron states within QCD sum rules
• On properties of the exotic hadrons from QCD sum rules
• Elastic and transition form factors of light pseudoscalar mesons from QCD sum rules