Garra Ticó, JordiGraugés Pous, EugeniBABAR Collaboration2019-04-052019-04-052008-10-171550-7998https://hdl.handle.net/2445/131518We 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 . We measure a cross section of σ ( e + e − → ρ + ρ − ) = 8.3 ± 0.7 ( stat ) ± 0.8 ( syst )     fb within the range of | cos  θ ∗ | < 0.8 and | cos  θ ± | < 0.85 , where θ ∗ is the center-of-mass polar angle of the ρ ± meson and θ ± are the angles in the ρ ± rest frame between the direction of the boost from the laboratory frame and the direction of the π ± . Assuming production through single-photon annihilation, there are three independent helicity amplitudes. We measure the ratios of their squared moduli to be | F 00 | 2 ∶ | F 10 | 2 ∶ | F 11 | 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 | F 00 | 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.9 p.application/pdfeng(c) American Physical Society, 2008Física de partículesExperimentsParticle physicsExperimentsinfo:eu-repo/semantics/article5776762019-04-05info:eu-repo/semantics/openAccess