Licentiate Thesis: Studies of Top Physics Sensitivity and of Pile-Up Effects on Energy Reconstruction in the ATLAS Detector

by Mr Simon Molander (Stockholms Universitet)

Friday 26 Feb 2016, 13:00 → 15:00 Europe/Stockholm

A4:1003

This thesis presents two studies conducted using the ATLAS detector at the Large Hadron Collider. The first one is a technical study about how out-of-time pile-up affects energy reconstruction using the optimal filtering 2 algorithm in the TILE calorimeter sub detector. The study is conducted using a pulse simulator software that is also described. Although the algorithm is potentially sensitive to the effects of out-of-time pile-up, the effects under actual running conditions are estimated to be lower than 1.5 ADC counts for 68 % of the pulses, which is considered a small effect. It is also shown that out-of-time pile-up is a potential reason to get negatively reconstructed energies. The second study regards a measurement of the t ¯t Z cross section with one hadronically decaying τ leptons and two lighter leptons in the final state using 8 TeV data. The conclusion is that it is not possible to make a significant such measurement from the 8 TeV data due to low efficiencies in reconstruction of τ leptons. In addition to these two studies, this thesis also contain brief overviews of the atlas detector and the standard model of particles and interactions.