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Confronting heavy-ion models with experimental data from LHC
Lelák, Emil ; Rybář, Martin (advisor) ; Poláček, Stanislav (referee)
The purpose of heavy-ion physics is to study the properties of strong interaction and matter under the extreme conditions that prevailed within a few millionths of a second after the Big Bang. These extreme conditions can be created when two relativistic heavy ions collide and a special matter called quark-gluon plasma is formed. The thesis deals with confronting models of proton-proton and heavy-ion collisions with experimental data from LHC. The thesis starts with the definition of basic kinematic quantities. Then, the facts about the LHC and the ATLAS experiment are provided. In the next part, the physics background concerning jets and the quark-gluon plasma is explained. Conse- quently, the description of used Monte Carlo simulations - PYTHIA 8 for proton-proton and JEWEL for heavy-ion collisions is provided. The important part of the thesis was to implement an analysis within the Rivet framework, which is described in the next part of the thesis. The implemented analysis was applied to data from simulations and the resulting distributions were compared to experimental data. As to results, PYTHIA 8 can describe well experimental jet spectra in proton-proton collisions. However, JEWEL does not describe heavy-ion collisions well, which is shown by the significant suppression of the jet spectrum from the...
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Search for an excited tau-lepton with the ATLAS experiment
Krsek, Kryštof ; Pleskot, Vojtěch (advisor) ; Poláček, Stanislav (referee)
Nowadays, Standard Model is describing leptons as final-state components, inclu- ding tau-leptons. Nevertheless we want to improve this model of particle physics and discover new physics beyond this model. These efforts are made not only on ATLAS ex- periment at CERN. Discover of excited tau-lepton would indicate an internal structure of tau-leptons and leptons in general. For final analysis of excited tau-leptons we need an accurate and validated background estimation. One of the main additions to bac- kground is pair production of ttbar which decays into very similar decay products as excited tau-leptons and therefore this background events often pass through signal se- lection criteria. Reliable validation of prediction for ttbar production is therefore very important for this analysis. Region, which is significantly enriched by ttbar events are collisions where electron, muon and 2b-jets were born. However, fake events also pass into this region, where is at least one physical object misidentificated. In our analysis we will try to estimate and validate fake background via correction factor, called fake factor (FF). This bachelor's thesis, as well as the whole analysis of searching for the excited tau-lepton, uses data from proton-proton collisions with a center of mass energy of 13 TeV, recorded by the...
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Tine calibration of the ATLAS Tile Calorimeter using jets
Poláček, Stanislav ; Davídek, Tomáš (advisor) ; Rybář, Martin (referee)
The ATLAS experiment is one of the two general-purpose detectors at the Large Hadron Collider at CERN near Geneva. The goals of this particle physics experiment are the search for new physics phenomena and precision measurement of the particle interactions. Tilecal is the central hadronic calorimeter of the ATLAS. The calorimeter time calibration is important for the time-of-flight measurement of particles (used in some analyses) as well as for the actual energy reconstruction. 1
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Response of the ATLAS Tile Calorimeter
Poláček, Stanislav ; Davídek, Tomáš (advisor) ; Novotný, Vladimír (referee)
Sandwich hadronic Tile Calorimeter is part of the ATLAS experiment at the Large Hadron Collider in European Organization for Nuclear Research CERN laboratory near Geneva in Switzerland. The goal of this thesis is to examine the response of parts of the Tile Calorimeter to the beam of electrons accelerated to energy of 100 GeV and the dependance of the electron signal on the beam impact point. 1
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