A combined study of the pion's static properties and form factors

Abstract

We study consistently the pion's static observables and the elastic and γ*γ-> π^0 transition form factors within a light-front model. Consistency requires that all calculations are performed within a given model with the same and single adjusted length or mass-scale parameter of the associated pion bound-state wave function. Our results agree well with all extent data including recent Belle data on the γ*γ-> π^0 form factor at large q^2, yet the BaBar data on this transition form factor resists a sensible comparison. We relax the initial constraint on the bound-state wave function and show the BaBar data can partially be accommodated. This, however, comes at the cost of a hard elastic form factor not in agreement with experiment. Moreover, the pion charge radius is about 40% smaller than its experimentally determined value. It is argued that a decreasing charge radius produces an ever harder form factor with a bound-state amplitude difficultly reconcilable with soft QCD. We also discuss why vector dominance type models for the photon-quark vertex, based on analyticity and crossing symmetry, are unlikely to reproduce the litigious transition form factor data.

14 pages, 7 figures, 2 Tables; minor changes; 2 new references added (Ref. 54 and 57); version to be published in Few Body Physics

References in corpus (11)

• Determination of the Charged Pion Form Factor at Q2=1.60 and 2.45 (GeV/c)2
• Measurement of gamma gamma* --> pi0 transition form factor at Belle
• Abelian anomaly and neutral pion production
• pi- and rho-mesons, and their diquark partners, from a contact interaction
• Light Cone Sum Rules for the pi0-gamma*-gamma Form Factor Revisited
• Pion form factor from a contact interaction
• Comparing antithetic trends of data for the pion-photon transition form factor
• Strong D* -> D+pi and B* -> B+pi couplings
• Pion and kaon elastic form factors in a refined light-front model
• Vector meson dominance and the pi^0 transition form factor
• On the ${\gamma }^{\ast }\gamma \to \pi (\eta ,{\eta }^{\prime })$ transition form factors

Cited by in corpus (4)

• Exciting flavored bound states
• Pion structure in the nuclear medium
• Spacelike and timelike form factors for the $({\pi }^0,\eta ,{\eta }^{\prime })\to {\gamma }^{\ast }\gamma$ transitions in the light-front quark model
• Electromagnetic spin-1 form-factor free of zero-modes