Search for Stop Using the ATLAS Detector and Performance Analysis of the Tile Calorimeter with Muons from W Decays

• Main Author: Andrean, Stefio Yosse
• Format: Others
• Language: English
• Published: Stockholms universitet, Fysikum 2021
• Subjects: particle physics; standard model; bsm; supersymmetry; stop; calorimeter; ATLAS; Subatomic Physics; Subatomär fysik
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-191555

This thesis presents a search for the supersymmetric partner of the top quark in the final state with one lepton. The search focuses especially in the region of the parameter space where the 2-body decay dominates. The analysis is performed using LHC full Run 2 data at √s = 13 TeV as recorded by the ATLAS detector. No significant excess above the backgrounds is observed, and 95% confidence level exclusion limits are calculated in the stop-neutralino mass plane. Stops are excluded up to 1200 GeV in the low neutralino mass scenario of below 400 GeV. The Tile Calorimeter is part of the ATLAS calorimeter system whose main task is to measure the energy of hadrons. A performance study is conducted on the Tile Calorimeter using muons from W boson decay originating from proton-proton collisions. Each calorimeter cell response is measure in data and compared with detector simulation.  The azimuthal cell response uniformity is also investigated using a likelihood method. Overall, a good data to detector simulation agreement and azimuthal uniformity is observed which shows well-calibrated cells and uniform responses among the calorimeter modules.