A study of muon-electron elastic scattering in a test beam

In 2018, a test run with muons in the North Area at CERN was performed, running parasitically downstream of the COMPASS spectrometer. The aim of the test was to investigate the elastic interactions of muons on atomic electrons, in an experimental configuration similar to the one proposed by the project MUonE, which plans to perform a very precise measurement of the differential cross-section of the elastic interactions. COMPASS was taking data with a 190 GeV π beam, stopped in a tungsten beam dump: the muons from these π decays passed through a setup including a graphite target followed by 10 planes of Si tracker and a BGO crystal electromagnetic calorimeter placed at the end of the tracker. The elastic scattering events were selected and analysed, and compared to expectations from MonteCarlo simulation. The agreement found was satisfactory and demonstrated that measuring the angles of the outgoing particles, a clean sample of elastic interaction could be identified.