Two Photon Interaction Measurements with the KLOE Small Angle Tagging System

The two photon processes γγ→π^(0 ),η,π^0π^0,π^+π^-,π^0 η,η^', expected in e-e+ collitions at DAPHNE, can be studied with high precision by introducing a small angle tagging facilities for the scattered electrons. We describe the design of the KLOE small angle tagging system to study γγ interactions at DAPHNE. This includes a COIL detector to tag particles hitting the SFM coils, a SAT detector to tag electrons passing through the SFM and a BREM detector for high energy photons in coincidence with tagged electrons in order to reject the radiative Bhabba events. Two such systems placed symmetrically with respect to the interaction point allow tagging both electrons and positrons. The maximum number of events/year that can be collected by this tagging system and the statistical error on the γγ→π^0π^0, cross section are also discussed.