Analysis of the π+ π- π+ π- and π+ π0 π- π0 final states in quasi-real two-photon collisions at LEP

The reactions γ γ → π+ π- π+ π- and γ γ → π+ π0 π- π0 are studied with the L3 detector at LEP in a data sample collected at centre-of-mass energies from 161 GeV to 209 GeV with a total integrated luminosity of 698 pb-1. A spin-parity-helicity analysis of the ρ0 ρ0 and ρ+ ρ- systems for two-photon centre-of-mass energies between 1 and 3 GeV shows the dominance of the spin-parity state 2+ with helicity 2. The contribution of 0+ and 0- spin-parity states is also observed, whereas contributions of 2- states and of a state with spin-parity 2+ and zero helicity are found to be negligible. © 2006 Elsevier B.V. All rights reserved.