Summer Student Project Report: Investigating calibration hits in the ATLAS calorimeter

Particle \now is a process in which information from all subdetectors are combined using various algorithms\nto reconstruct objects with the most accurate measurements of a particle's momentum and energy. For the\nATLAS experiment, the largest improvement would be to reject pileup contributions in the calorimeter by as-\nsociating those energy deposits to additional vertices using their track measurements. This report summarises\nan investigation into the clustering behaviour in the ATLAS calorimeter using specially generated les that\ninclude calibration hits. It contributes to a larger project in which the aim is to develop and improve the\nalgorithms used to construct particle \now objects, with the overarching object being the rejection of pileup.\nInitial results show that a signicant fraction of particles produce more than one cluster or none at all. These\nconditions, however, are shown to have an and pT dependence, which will help us reject particles that are\nlikely not going to produce a single cluster only.