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Studies of Long-Lived Supersymmetric Top Quarks and Online Monitoring of the ATLAS First Level Calorimeter Trigger
Stockholm University, Faculty of Science, Department of Physics. (Elementary Particle Physics)
2010 (English)Doctoral thesis, monograph (Other academic)
Abstract [en]

The Large Hadron Collider (LHC) has recently started colliding protons  at  7 TeV centre-of mass energy. Extensive searches for hitherto unobserved particles and physics processes will be made as part of an ambitious scientific programme which aims to answer some of the fundamental questions in modern physics. The ATLAS detector, designed to discover a wide range of physics processes, will play a crucial part in these searches.

The First Level Calorimeter Trigger is one of the first steps in the ATLAS data acquisition chain. Excellent performance at this stage is required to fully make use of the ATLAS potential for discovery of new physics processes. Online monitoring of the First Level Calorimeter Trigger is therefore of great importance to ensure good quality of data and correct performance of the trigger.  As part of the overall online trigger monitoring this thesis describes the monitoring of the Jet/Energy-sum Processor, responsible for defining the first jet candidates and summation of the total energy deposited in the ATLAS calorimeters.

Supersymmetry is one of the most studied models of physics beyond the Standard Model. Some supersymmetric models give rise to long-lived stop squarks or gluinos which, if produced at the LHC,  immediately will form exotic hadrons, called R-hadrons. The discovery or non-discovery of R-hadrons can provide important information about physics beyond the Standard Model and searches for these particles are therefore a part of the ATLAS scientific programme. This thesis investigate the capability of the ATLAS detector to discover stop R-hadrons using different track configurations and ß measured by the calorimeters. A technique for measuring the R-hadron mass using time-of-flight information from the ATLAS  muon detectors is demonstrated as well. Included in this thesis is also a phenomenological study of the possibility for a long-lived stop squark to arise in supersymmetric models where the neutralino is the lightest supersymmetric particle. The conditions for the stop to be long-lived as well as the implications it has on the  dark matter density and the supersymmetric mass  spectra  are studied in detail.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University , 2010. , 178 p.
Keyword [en]
particle physics, fundamental questions in physics, supersymmetry, stable massive particles, LHC, the ATLAS experiment, the level-1 calorimeter trigger, CERN
National Category
Subatomic Physics
Research subject
URN: urn:nbn:se:su:diva-38764ISBN: 978-91-7447-080-2OAI: diva2:315394
Public defence
2010-06-04, sal FB42, AlbaNova universitetscentrum, Roslagstullbacken 21, Stockholm, 13:00 (English)
Available from: 2010-05-11 Created: 2010-04-28 Last updated: 2010-04-30Bibliographically approved

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