Studies of beam-induced background processes for searches in delayed-jet final states with the ATLAS detector

Sammanfattning

When searching for new elementary particles at collider experiments, estimation of background processes is one of the most challenging and fundamental components. This is particularly true when the search is focused on extremely rare events from models of new physics beyond the standard model. This thesis aims to study beam-induced background characteristics in the granularity of the single cells within the calorimeter subsystems, to reject unwanted particles for exotic long-lived particles delayed jets analysis. The method relies on the relation between time, spatial coordinate z and radial distance R for different types of particles. Dedicated non-collision background datasets are compared to Monte Carlo simulated long-lived particles signal data, using single cells as fitting points for cluster discrimination. A first rejection method for single beam-induced background clusters is successfully studied and described, highlighting important limitations about the computed timing sensitivity of the calorimeters.