Observation of e+e- annihilation into the C=+1 hadronic final states ρ0ρ0 and ρ0

We report the first observation of e+e- annihilation into states of positive C parity, namely, ρ0ρ0 and ρ0. The two states are observed in the π+π-π+π- and K+K-π+π- final states, respectively, in a data sample of 225fb-1 collected by the BABAR experiment at the Positron-Electron Project II e+e- storage rings at energies near s=10.58GeV. The distributions of cos θ*, where θ* is the center-of-mass polar angle of the meson or the forward ρ0 meson, suggest production by two-virtual-photon annihilation. We measure cross sections within the range |cos θ*|<0.8 of σ(e+e-→ρ0ρ0)=20.7±0.7(stat) ±2.7(syst)fb and σ(e+e-→ρ0)=5.7±0.5(stat)±0. 8(syst)fb.