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Electroweak bosons as probes of quark-gluon plasma
Jirásek, Radek ; Rybář, Martin (advisor) ; Faltová, Jana (referee)
Title: Electroweak bosons as probes of quark-gluon plasma Author: Radek Jirásek Department: Institute of Particle and Nuclear Physics Supervisor: Mgr. Martin Rybář, Ph.D, Institute of Particle and Nuclear Physics Abstract: This thesis is focused on heavy-ion physics which aims to improve our understanding of the strong interaction as well as of the quark-gluon plasma. Such an exotic state of matter exists only in the extreme conditions which could be achieved in the lead-lead collisions in the LHC at CERN. Hence we will discuss the physics of accelerators and detectors. We will outline the structure and properties of the ATLAS experiment, one of the detectors on the LHC. Later, we aimed at the physics behind the heavy-ion collisions. We describe what the quark-gluon plasma is and how we can use electroweak bosons to probe it. Basic of our analysis procedures will be introduced, as well as the principles of simulation of data with the Pythia8 model. The main goal of this work is to study the re-clustering of the jets and how that changes their properties. Then we focused on the properties of the electroweak bosons and how they could help us with the study of the quark-gluon plasma. In the end, we estimate the number of events that could be expected to observe in future measurements on ATLAS in heavy-ion...
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Kalibrace a určování druhu jetů pomocí technik strojového učení
Novotný, Patrik ; Rybář, Martin (advisor) ; Federič, Pavol (referee)
Title: Exploring jet calibration and jet tagging with machine learning techniques Author: Bc. Patrik Novotný Institute: Institute of Particle and Nuclear Physics Supervisor: Mgr. Martin Rybář, Ph.D., Institute of Particle and Nuclear Physics Abstract: The presented thesis has two goals. First, it aims to improve the energy calibration of jets, collimated sprays of particles measured in the ATLAS experiment. Jets are considered to be a powerful tool for studying the properties of the quark-gluon plasma produced in heavy-ion collisions at the LHC. Apart from the kinematics properties of the jet, a key information that might play a role in the interaction of jets with the quark-gluon plasma is the "flavor" of the initiating hard parton. The classification of jets according to flavor is the second of the research aims. The work in the thesis explores using various machine learning techniques contained in the TensorFlow and cuML software libraries, which allow computations to be performed on graphics cards to address these two goals. The variables investigated are six variables related to the kinematics of the jet and 24 variables related to the energy deposited in different parts of the ATLAS detector. The differences between the various machine learning models and their settings are extensively discussed....
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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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The Marketing Strategies of Apple Inc and Their Change After 2011
Rybář, Martin ; Halada, Jan (advisor) ; Shavit, Anna (referee)
Thesis on "The Marketing Strategies of Apple Inc. and Their Change After 2011" deals with the transformation of Apple's marketing strategies after the death of Steve Jobs, who was regarded by many as a key figure in the whole company. The author aims to present the company, products and marketing strategies used by Steve Jobs and then analyze the changes that have been made by new CEO Tim Cook since 2011. The theoretical part is devoted to definitions, which the author will be using in the practical part. A major part of this thesis is quantitative research that analyzes consumer perception of Apple Inc. in the Czech Republic completed with recommendations for the future success.
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Exploring jet calibration with machine learning techniques
Novotný, Patrik ; Rybář, Martin (advisor) ; Žlebčík, Radek (referee)
Title: Exploring jet calibration with machine learning techniques Author: Patrik Novotný Institute: Institute of Particle and Nuclear Physics Supervisor: Mgr. Martin Rybář, Ph.D., Institute of Particle and Nuclear Physics Abstract: Jets, collimated sprays of particles, are considered to be a perfect probe of the matter created at heavy-ion collisions. The work explores the possibility of using machine learning techniques to improve the overall calibration of jet energy scale and its resolution for ATLAS experiment calorimeters, which are used in the research of lead nucleus collisions. First, the current performance of jet reconstruction quantified by mean response and energy resolution dependence on the value of transverse momentum, pseudorapidity, and centrality of collisions is shown. It is further discussed that the current calibration does not take into account whether the jets are induced by a quark or gluon. Subsequently, four variables are selected, which might be used to distinguish between these two groups of jets. The dependence of the response on those quantities and on centrality is further studied. The last part describes the process of the preparation of a training data set, set up of the neural network, and the analysis of it using tools provided by the MultiLayerPerceptron library of the...
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Tests of Semiconductor Detectors for ATLAS Upgrade
Martaus, Marek ; Kodyš, Peter (advisor) ; Rybář, Martin (referee)
The semiconductor detectors of ATLAS experiment at CERN are exposed to high radiation for a long time, which reduces their efficiency. They need to be replaced and, if necessary, modernized. Nowadays, the entire Large Hadron Collider is planned to improve. Its luminosity will increase. During this shut- down, the detectors of ATLAS experiment will also be upgraded. This thesis is focused on strip detectors of a new inner detector of ATLAS experiment called ITk. For the correct interpretation of the measured results, it is important to know the detector's response. Test of detector response is, therefore, an important part of the process of developing. In this thesis, we focused on detectors' edges, where we assumed a different shape of the electric field, which may cause a different response. We chose the laser test because it is a position-sensitive measurement. 1
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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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The Marketing Strategies of Apple Inc and Their Change After 2011
Rybář, Martin ; Halada, Jan (advisor) ; Shavit, Anna (referee)
Thesis on "The Marketing Strategies of Apple Inc. and Their Change After 2011" deals with the transformation of Apple's marketing strategies after the death of Steve Jobs, who was regarded by many as a key figure in the whole company. The author aims to present the company, products and marketing strategies used by Steve Jobs and then analyze the changes that have been made by new CEO Tim Cook since 2011. The theoretical part is devoted to definitions, which the author will be using in the practical part. A major part of this thesis is quantitative research that analyzes consumer perception of Apple Inc. in the Czech Republic completed with recommendations for the future success.
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Study of jets in p+p and Pb+Pb collisions at LHC
Rybář, Martin ; Dolejší, Jiří (advisor) ; Bielčíková, Jana (referee) ; Kupčo, Alexander (referee)
Highly energetic jets are considered to be a direct probe of hot and dense QCD medium created in heavy ion collisions. Jet measurements performed both at the LHC and RHIC indicate a presence of the jet quenching phenomenon. This thesis summarizes ATLAS jet heavy ion measurements and it reports the first exploratory study of properties of the multi-jet production in heavy ion collisions presented in terms of yield of neighbouring jets. The work is expected to shed a light on the process of the parton energy loss. The measurement is performed using the Pb+Pb collision data collected by ATLAS detector during the 2011 LHC runs at the nucleon-nucleon center of mass energy of 2.76 TeV. 1
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