Vector meson dominance and the pi^0 transition form factor

It is shown that the pi^0 transition form factor F(Q_1^2,Q_2^2) differs substantially from its one-real-photon limit F(Q_1^2,0) even for rather small values of Q_2^2 (approx 0.1 GeV^2), which cannot be excluded in experiments with one "untagged" electron. It indicates that the comparison of data with theoretical calculations, which usually assume Q_2^2=0, may be untrustworthy. Our phenomenological model of the pi^0 transition form factor is based on the vector-meson-dominance hypothesis and all its parameters are fixed by using the experimental data on the decays of vector mesons. The model soundness is checked in the two-real-photon limit, where it provides a good parameter-free description of the pi^0 -> 2 gamma decay rate, and in the pi^0 Dalitz decay. The dependence of F(Q_1^2,Q_2^2) on Q_1^2 at several fixed values of Q_2^2 is presented and the comparison with existing data performed.Comment: A slightly abbreviated version has been published as a Brief Report in Physical Review

New narrow resonance in the e+e−→ϕηe^+ e^- \to \phi\eta data by Belle collaboration

Fitting the recent e^+e^-\ra\phi\,\eta data by the Belle collaboration with a theoretical formula reveals, besides the dominant $\phi(1680)$ resonance, two narrow resonances: expected $\phi(2170)$ resonance and an unexpected resonance with the mass of about 1851 MeV. Close proximity to the $X(1835)$ resonance suggests that the new resonance may be interpreted as the $p \bar p$ baryonium in an excited state. Follow-up analysis found the same resonance also in e^+e^-\ra\omega\,\eta data by CMD-3 experiment.Comment: 3 pages, 3 figure