## Pion form factor and reactions e^+e^---> omega pi^0 and e^+e^---> pi^+ pi^- pi^+ pi^- at energies up to 2 -- 3 GeV in the many-channel approach    [PDF]

N. N. Achasov, A. A. Kozhevnikov
Using the field-theory-inspired expression for the pion electromagnetic form factor F_\pi, a good description of the data in the range -10pi^+ pi^- is obtained at energies up to 3 GeV. The inclusion of the VP and AP loops demands the treatment of the reactions e^+e^---> omega pi^0 and e^+e^---> pi^+ pi^- pi^+ pi^-. This task is also made, with the SND data on the omega pi^0 production and the BABAR data on the pi^+ pi^- pi^+ pi^- production, both in e^+e^- annihilation, upon taking into account \rho(770) and the heavier \rho(1450), \rho(1700), and \rho(2100) resonances. The problems with inclusion of the VP and AP loops are pointed out and discussed.
View original: http://arxiv.org/abs/1305.6117