The total hadronic cross section for virtual photon-photon interactions is reported for center-of-mass energy, W, between 2 and 20 GeV. The data were obtained via the process e+e−→e+e−γ*γ*→e e−++hadrons with both scattered e+ and e− detected. Each photon’s four-momentum squared, q2, ranges from -0.1 to -1.6 GeV2. Dependence upon q2 agrees with a generalized vector-meson-dominance model. The total cross section shows little W dependence, averaging 125 nb at q12=q22=-0.3. Photon helicity interference terms are determined.
CROSS SECTION EXTRAPOLATED USING THE GENERALISED VECTOR CT. = Data are for >= 3 hadrons. DOMINANCE MODEL TO Q1=Q2=0.
Data are for >= 3 hadrons.
Data are for >= 3 hadrons.
The total hadronic cross-section sigma_gg(W) for the interaction of real photons, gg->hadrons, is measured for gg centre-of-mass energies 10<W<110 GeV. The cross-section is extracted from a measurement of the process e+e- -> e+e-g*g* -> e+e- hardrons, using a luminosity function for the photon flux together with form factors for extrapolating to real photons (Q^2=0 GeV^2). The data were taken with the OPAL detector at LEP at e+e- centre-of-mass energies 161, 172 and 183 GeV. The cross-section sigma_gg(W) is compared with Regge factorisation and with the energy dependence observed in gp and pp interactions. The data are also compared to models which predict a faster rise of sigma_gg(W) compared to gp and pp interactions due to additional hard gg interactions not present in hadronic collisions.
No description provided.
No description provided.