Hadron production in two-photon collisions at LEP-L3

TL;DR

This paper analyzes hadron production in two-photon collisions at LEP, measuring cross sections across a wide energy range and comparing results with theoretical models and Monte Carlo simulations.

Contribution

It provides the first detailed measurements of two-photon hadron production cross sections at LEP energies and compares them with Regge parametrisation and theoretical models.

Findings

Cross sections follow Regge behaviour with a steeper energy rise.

Data agree with some theoretical models but show deviations at higher energies.

Monte Carlo generators Pythia and Phojet are used for comparison.

Abstract

The reaction e+ e- -> e+ e- gamma* gamma* -> e+ e- hadrons is analysed for quasi-real virtual photons using data collected by the L3 detector during the LEP high energy runs at sqrt(s) = 183 and 189 GeV. Preliminary results on the cross sections sigma(e+e- -> e+e- hadrons) and sigma(gamma gamma -> hadrons) are given in the interval 5 GeV < W_{gamma gamma} < 145 GeV. The centre-of-mass energy dependence of the two-photon cross section is well described by the universal Regge parametrisation, but with a steeper rise with energy as compared to hadron-hadron cross sections. The data are also compared to the expectations of different theoretical models. To investigate diffractive processes, the elastic gamma gamma -> rho0 rho0 process and the inclusive rho0 production gamma gamma -> rho0 X are studied in the W_{gamma gamma} > 3 GeV region. In all channels a comparison is made with the Pythia and Phojet Monte Carlo generators.