Calorimetry for MUonE

The muon anomalous magnetic moment is one of the most precisely measured quantity, as one of the most precisely calculable in the Standard Model. The latest measurements from FNAL g-2 experiment, that confirmed the previous ones from BNL, are highlighting a significant discrepancy from the theory prediction. A new experiment, whose purpose is to help solving this dispute, is the MUonE experiment. The MUonE experiment aims to measure the differential cross section of μe elastic scattering, by colliding the 160 GeV muons of the CERN M2 beam with the atomic electrons of several beryllium (Be) targets. The precise characterization of the differential cross section’s shape will allow to make an independent determination of the leading hadronic contribution to the magnetic moment, which is the main theoretical uncertainty to date. This thesis contributes to the study of the performance of the electromagnetic calorimeter of the MUonE experiment, in view of the first test beam scheduled for July 2022. The experimental apparatus for the full experiment will consist in 40 tracking stations of one meter length, equipped with two Be targets and three couples of silicon (Si) sensors each, and an electromag- netic calorimeter (ECAL). Regarding the first test beam of July, only a reduced geometry setup will be used, and it will include two tracking stations and the ECAL. In order to understand the behaviour of the calorimeter, simulation studies are necessaries and, to reach the accuracy needed in the shape of the differential cross section, a huge statistics of data is required. As a consequence, full simulation studies will be a computational challenge even at a preliminary level. Therefore, a FastSimulation algorithm has been developed, with detector effects parameterized from (smaller and dedicated) Full Simulation samples. The first version of this tool simulates the propagation of the particles through the tracking stations, from a pre-generated set of MC NLO events (high energy muons scattering on electrons at rest, with at maximum one real photon emitted). It takes into account the effect of multiple scattering due to layers of Be and Si, and the kinematical properties of the beam (divergence and beam spot). Moreover, the response of the calorimeter is simulated using the GFLASH parametrization by CMS. The first step of this thesis work consists in the update of the FastSim algorithm in order to make use of the existing parametrization of the tracking stations and ECAL in the new version of the code. In this new version NNLO events are directly generated in the simulation thanks to the MESMER MC generator and then analyzed through the c++ interface. In this way a preliminary analysis can be done also on events where two real photons are produced. As a second step, to further improve the precision of this simulation, it will be necessary to integrate in the description of the particles prop- agation the effect of energy loss due to Bremsstrahlung of electrons and Pair Production of photons. While, concerning the calorimeter, the electronic noise will be incorporated in the description of the detector response. Moreover, since the purpose of the simulations is to optimize the detector energy resolution, the use of machine-learning based techniques will help reconstruct partial information on the energy deposit of the particles in the ECAL. Finally, working with the MUonE collaboration, I will have the opportunity to take part to the 3rd MUonE general collaboration meeting at CERN, taking place on May 11-12, and to the test beam scheduled for July 2022. Therefore, as conclusion of the thesis, the data from the simulations will be compared with the data collected from the test beam and with the ECAL prototype performances studied in lab tests at Legnaro.