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

The reaction γγ → π+π-π0 with quasi-real photons is studied with a total integrated luminosity of 663 pb-1, 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(π+π-π0)≤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 Γγγ Br(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. (orig.)