Total cross-section and diffractive $\rho^{0}$ production in $\gamma\gamma$ collisions at L3

The reaction e/sup +/e/sup -/ to e/sup +/e/sup -/ gamma * gamma * to e/sup +/e/sup -/hadrons is analysed for quasi-real virtual photons using data collected by the L3 detector during the LEP high energy runs at square root (s)=183 and 189 GeV. Preliminary results on the cross sections sigma (e/sup +/e/sup -/ to e/sup +/e/sup -/hadrons) and sigma ( gamma gamma to hadrons) are given in the interval 5 Ge V<or=W/sub gamma gamma /<or=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 to rho /sup 0/ rho /sup 0/ process and the inclusive rho /sup 0/ production gamma gamma to rho /sup 0/X are studied in the W/sub gamma gamma />or =3 GeV region. In all channels a comparison is made with the PYTHIA and PHOJET Monte Carlo generators. (16 refs).