Beam Tests of a Multilayer LumiCal Prototype

LumiCal is a sampling electromagnetic calorimeter designed for the precise measurement of integrated 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 silicon 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 transverse structure of the observed electromagnetic shower and the Moli\`ere radius measurement. A comparison with MC simulation is also discussed.