Coherent p0 and w0 photoproduction off germanium and silicon

The photoproduction of the p and the w was studied using data taken by the NA1 experiment at the CERN SPS. The beam was that of a tagged photon with energy between 70-225 GeV incident on an active target, which consisted of a monolithic germanium block and strips of silicon detector. The decay products were detected by the forward FRAMM spectrometer. The p and the w events were identified by their decays into and channels respectively. Using clean samples of events and taking into account their respective branching ratios and simulated geometrical acceptances the ratio was measured to be 9.64 +/- 0.54. The interaction-point distribution of a trimmed sample of p events resulted in the ratio of the interaction rates in the germanium and the silicon parts of the target, leading to the value of a, which describes the A-dependence of the nuclear cross-section by [equation] where A is the nuclear mass number. The measured [alpha] values for the overall and the coherent event samples, respectively, are [alpha = 1.45 +- 00.5 and [alpha]Coh = 1.44+-0.06.