CROSS-SECTION OF THE REACTION E+E--]PI+PI-PI+PI- FOR CENTER OF MASS ENERGIES FROM 890-MEV TO 1100-MEV

We present the results of a measurement of the cross section oof the reaction e+e- → π+π-π+π- from 890 to 1100 MeV in the center of mass, obtained with a magnetic detector at the Orsay Storage Ring ACO. With respect to previous experiments, the present one offers the possibility of reconstructing events with at least one constraint and his improved statistics. We find that our measurement of the cross section for e+e- → π+π-π+π- is compatible with quasi two-body production of πA1(mA1 = 1.1 GeV, ΓA1 ∼ 0.2-0.3 GeV), through the ρ{variant} and ρ{variant}′(1600) intermediate states. We were able to states. We were able to determine the cross section of this reaction at the energy of the φ meson and consequently an upper limit on the branching ratio of φ → π+π-π+π-. © 1979.