Partial wave analysis of πππ production in two-photon collisions at LEP

The reaction γγ → πππ with quasi-real photons is studied with a total integrated luminosity of 663 pb, collected by the L3 detector at LEP at center-of-mass energies from 183 to 209GeV. The results of an energy-dependent partial wave analysis in the mass region 1.1 ≤M(πππ) ≤ 2.2GeV are presented. The reaction is dominated by a2(1320) formation. A strong signal consistent with the first radial excitation of the isovector tensor state, a2(1700), is present and confirms the previous L3 observation. Its two-photon partial width is found to be ΓγγBr(3π) = 0.37 +0.12 −0.08 keV, the relative branching ratio of ρ(770)π to f2(1270)π is 3.4± 0.4. For all observed states the product of γγ partial width and 3π branching ratios is measured. PACS. 11.80.Et Partial-wave analysis – 13.60.Le Meson production – 13.25.-k Hadronic decays of mesons – 14.40.-n Mesons