Observation of e+e- to ρ+ρ- near √s = 10.58/gev

The authors report the first observation of e+e- → ρ+ρ-, in a data sample of 379 fb-1 collected with the BABAR detector at the PEP-II e+e- storage ring at center-of-mass energies near √s = 10.58 GeV. The authors measure a cross section of σ(e+e- → ρ+ρ-) = 19.5 ± 1.6(stat) ± 3.2(syst) fb. Assuming production through single-photon annihilation, there are three independent helicity amplitudes. They measure the ratios of their squared moduli to be |F00|2 : |F10|2 : |F11|2 = 0.51 ± 0.14(stat) ± 0.07(syst) : 0.10 ± 0.04(stat) ± 0.01(syst) : 0.04 ± 0.03(stat) ± 0.01(syst). The |F00|2 result is inconsistent with the prediction of 1.0 made by QCD models with a significance of 3.1 standard deviations including systematic uncertainties