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ISSN - 15507998, Physical Review D - Particles, Fields, Gravitation and Cosmology, 2008, vol. 78, p. -

Observation of e+e-→ρ+ρ- near s=10.58GeV

Aubert B., Bona M., Karyotakis Y., Lees J. P., Poireau V., Prencipe E., Prudent X., Tisserand V., Tico J. Garra, Grauges E., Lopez L., Palano A., Pappagallo M., Eigen G., Stugu B., Sun L., Abrams G. S., Battaglia M., Brown D. N., Cahn R. N., Jacobsen R. G., Kerth L. T., Kolomensky Yu G., Kukartsev G., Lynch G., Osipenkov I. L., Ronan M. T., Tackmann K., Tanabe T., Hawkes C. M., Soni N., Watson A. T., Koch H., Schroeder T., Walker D., Asgeirsson D. J., Fulsom B. G., Hearty C., Mattison T. S., McKenna J. A., Barrett M., Khan A., Teodorescu L., Blinov V. E., Bukin A. D., Buzykaev A. R., Druzhinin V. P., Golubev V. B., Onuchin A. P., Serednyakov S. I., Skovpen Yu I., Solodov E. P., Todyshev K. Yu, Bondioli M., Curry S., Eschrich I., Kirkby D., Lankford A. J., Lund P., Mandelkern M., Martin E. C., Stoker D. P., Abachi S., Buchanan C., Gary J. W., Liu F., Long O., Shen B. C., Vitug G. M., Yasin Z., Zhang L., Sharma V., Campagnari C., Hong T. M., Kovalskyi D., Mazur M. A., Richman J. D., Beck T. W., Eisner A. M., Flacco C. J., Heusch C. A., Kroseberg J., Lockman W. S., Schalk T., Schumm B. A., Seiden A., Wang L., Wilson M. G., Winstrom L. O., Cheng C. H., Doll D. A., Echenard B., Fang F., Hitlin D. G., Narsky I., Piatenko T., Porter F. C.

We report the first observation of e+e-→ρ+ρ-, in a data sample of 379fb-1 collected with the BABAR detector at the PEP-II e+e- storage ring at center-of-mass energies near s=10.58GeV. 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 |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. © 2008 The American Physical Society.