Analysis of the π ⁺π ^-π⁺π ^- and π⁺π⁰π^- π⁰ final states in quasi-real two-photon collisions at LEP

Abstract

The reactions γγ→π⁺π^- π⁺π^- and γγ→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 ρ⁰ρ⁰ 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.