Beam Tests of a Multilayer LumiCal Prototype

LumiCal is a sampling electromagnetic calorimeter designed for the precise measurement of in- tegrated luminosity in electron positron linear collider experiments. The present report contains a description and results of the first beam test of a multilayer LumiCal prototype with four sili- con detector planes. A 5 GeV electron beam from the CERN PS T9 facility was used to study the performance of the LumiCal prototype. Presented results are mainly focused on the trans- verse structure of the observed electromagnetic shower and the Molière radius measurement. A comparison with MC simulation is also discussed.