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Studies of Top Physics Sensitivity and of Pile-Up Effects on Energy Reconstruction in the ATLAS Detector: A Licentiate Thesis About the Treatment of Troublesome $\tau$ and Producing Pulses to Probe Pile-up Problems
Stockholm University, Faculty of Science, Department of Physics.ORCID iD: 0000-0002-1310-6141
2016 (English)Licentiate thesis, monograph (Other academic)
##### Abstract [en]

This thesis presents two studies conducted using the ATLAS detectorat the Large Hadron Collider. The first one is a technical study abouthow out-of-time pile-up affects energy reconstruction using the optimalfiltering 2 algorithm in the TILE calorimeter sub detector. The studyis conducted using a pulse simulator software that is also described.Although the algorithm is potentially sensitive to the effects ofout-of-time pile-up, the effects under actual running conditions areestimated 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-timepile-up is a potential reason to get negatively reconstructed energies.The second study regards a measurement of the $t\bar{tZ}$ cross sectionwith one hadronically decaying $\tau$ leptons and two lighter leptonsin the final state using 8 TeV data. The conclusion is that it isnot possible to make a significant such measurement from the 8 TeVdata due to low efficiencies in reconstruction of $\tau$ leptons.In addition to these two studies, this thesis also contain brief overviewsof the atlas detector and the standard model of particles and interactions.

##### Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University , 2016. , 86 p.
##### Keyword [en]
tau, top quark, ATLAS, LHC, TILE calorimeter, sensitivity, cross-section, standard model, physics, optimal filtering, energy reconstruction, hadronic tau decay
##### National Category
Subatomic Physics Accelerator Physics and Instrumentation
Physics
##### Identifiers
OAI: oai:DiVA.org:su-126258DiVA: diva2:899538
##### Presentation
2016-02-26, A4:1003, Alba Nova, Roslagstullsbacken 21, Stockholm, 13:00 (English)
##### Funder
Swedish Research Council, 1013219 Available from: 2016-03-01 Created: 2016-01-27 Last updated: 2016-03-01Bibliographically approved

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Molander, Simon
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Department of Physics
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Subatomic PhysicsAccelerator Physics and Instrumentation