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

Abstract

The reactions <math><mi is="true">γ</mi><mi is="true">γ</mi><mo is="true">→</mo><msup is="true"><mi is="true">π</mi><mo is="true">+</mo></msup><msup is="true"><mi is="true">π</mi><mo is="true">−</mo></msup><msup is="true"><mi is="true">π</mi><mo is="true">+</mo></msup><msup is="true"><mi is="true">π</mi><mo is="true">−</mo></msup></math> and <math><mi is="true">γ</mi><mi is="true">γ</mi><mo is="true">→</mo><msup is="true"><mi is="true">π</mi><mo is="true">+</mo></msup><msup is="true"><mi is="true">π</mi><mn is="true">0</mn></msup><msup is="true"><mi is="true">π</mi><mo is="true">−</mo></msup><msup is="true"><mi is="true">π</mi><mn is="true">0</mn></msup></math> 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 p0p0 and p+p- 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.