Two photon results from TASSO
Two photon annihilation processes were observed with the TASSO detector at the e+e- storage ring PETRA. We report on the analyses of untagged and single tag events.
We select untagged events with a two prong final state seen in the central detector and compare these data to the prediction for two photon QED processes. We observe an excess of events in the expected invariant mass range for the fo. The single tag events with two prongs seen in the central detector show a very good agreement to the QED prediction in all measured distributions. Multihadronic events with a single tag are interpreted in terms of electron photon scattering. The observed transverse momentum distribution of the hadrons exhibits an exponential fall-off at lower momenta up to about 1 GeV/c; beyond this the distribution flattens off. This may point to two different couplings of the photon to hadrons, a VDM-like and a pointlike coupling. From an overall fit to the measured distributions of these data we derive mean charged multiplicities and cross sections for hadron production as a function of the total energy of the two photon system.
KeywordsInvariant Mass Beam Axis Lepton Pair Photon Production Central Detector
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