PION FORM FACTOR AND REACTIONS e+e− → ωπ0 AND e+e− → π+π−π+π− AT ENERGIES UP TO 2 – 3 GEV IN THE MANY-CHANNEL APPROACH

Using the field-theory-inspired expression for the pion electromagnetic form factor Fπ, a good description of the data in the range -10 < s < 1 GeV2 is obtained upon taking into account the pseudoscalar-pseudoscalar (PP) loops. When the vector-pseudoscalar (VP) and the axial vector-pseudoscalar (AP) loops are taken into account in addition to the PP ones, a good description of the BABAR data on the reaction e+e− → π+π− is obtained at energies up to 3 GeV. The inclusion of the VP and AP loops demands the treatment of the reactions e+e− → ωπ0 and e+e− → π+π−π+π−. This task is performed with the SND data on ωπ0 production and the BABAR data on π+π−π+π− production, both in e+e− annihilation, by taking into account ρ(770) and the heavier ρ(1450), ρ(1700), and ρ(2100) resonances. The problems arising from including of the VP and AP loops are pointed out and discussed.

CHIRAL ANOMALY EFFECTS AND THE BABAR MEASUREMENTS OF THE γγ* → π0 TRANSITION FORM-FACTOR

The recent BaBar measurements of the γγ*→π0 transition form-factor show spectacular deviation from perturbative QCD prediction for large spacelike Q2 up to 34 GeV2. When plotted against Q2, Q2F(Q2) shows steady increase with Q2 in contrast with the flat Q2 behavior predicted by perturbative QCD, and at 34 GeV2 is more than 50% larger than the QCD prediction. Stimulated by the BaBar measurements, we revisit our previous paper on the cancellation of anomaly effects in high energy processes Z0→π0γ, e+e- → π0γ and apply our results to the γ*γ→π0 transition form-factor measured in the e+e- → e+e-π0 process with one highly virtual photon. We find that, the transition form-factor F(Q2) behaves as [Formula: see text] and produces a striking agreement with the BaBar data for Q2F(Q2) with m = 132 MeV which also reproduces very well the CLEO data at lower Q2.