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Study of the extremely rare decay K+ -> pi+nu nu with the NA62 experiment at CERN
Zamkovský, Michal ; Kampf, Karol (advisor) ; Blažek, Tomáš (referee) ; Řezníček, Pavel (referee)
The decay K+ → π+ ν¯ν has one of the most precisely predicted branch- ing ratio at the level of 10−10 . It is forbidden at the tree level, which makes it sensitive to the effects of new physics. The NA62 experiment at the CERN SPS aims to measure the branching ratio of the K+ → π+ ν¯ν using a unique decay-in-flight technique. NA62 took data so far in 2016-2018. The statistics acquired in 2016 allowed to reach Standard Model sensi- tivity for K+ → π+ ν¯ν. Owing to the statistics collected in 2017, NA62 surpasses the present best sensitivity. In the scope of this thesis, the preliminary result obtained from 2017 data sample is reported. 1
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Simulation and Tests of Strip Semiconductor Detectors for ATLAS Upgrade
Theiner, Ondřej ; Kodyš, Peter (advisor) ; Řezníček, Pavel (referee)
Together with the ongoing works on preparations of High-Luminosity LHC, there is a need to enhance the performance of various experiments on the collider as well. This is also the case of the experiment ATLAS and its subdetectors such as Inner Detector which will be completely replaced by new all-silicon Inner Tracker (ITk). This thesis deals with computer simulations of silicon strip detec- tors for ATLAS Upgrade ITk. For this purpose, we are using framework AllPix2 . It enables to simulate everything from the interaction of the particle with silicon, charge propagation in electric and magnetic fields, charge collection, up to signal digitization. We focused mostly on three aspects in the simulations. The first is a precise characterization of used detectors, the second is a simulation of a test beam measurements and the third one is a simulation of test measurements with a radioactive beta source. We also discussed the possibility of simulation of test measurements with a laser. These simulations are important not only because they help us to better understand processes happening inside the detector, but they are also used as a validation of testing measurements. As a result of this, we are able to point out the effects of the experimental setup (or detector itself) which have an impact on measured...
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Study of charmonia production in proton-proton and heavy-ion collisions at the LHC
Krivoš, Martin ; Spousta, Martin (advisor) ; Řezníček, Pavel (referee)
In this thesis a production of J/ψ meson in pp and heavy-ion collisions was investigated. A comparison between Monte Carlo generator and data by ATLAS experiment at CERN was done. PYTHIA version 8.2 was chosen for the Monte Carlo generator. In the first part, comparisons of several configurations of PYTHIA were used to establish the best matching of the Monte Carlo to the data using collisions with centre-of-mass energy of 7 TeV. Choice of parton distribution functions was found not to be important, while presence or absence of initial and final state radiation were proven to have an important impact on the result. In the second part, correlation of J/ψ meson and the jet production was quantified. Anti-kt algorithm with R = 0.4 was used to reconstruct jets. Pairs of muons were used to identify J/ψ meson candidates. Only less than 10% of J/ψ mesons were found to be associated with jets. 1
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Automation of Semiconductor Detector Tests for ATLAS Upgrade
Martaus, Marek ; Kodyš, Peter (advisor) ; Řezníček, Pavel (referee)
After many years of operation of a Large Hadron Collider, it is necessary to modernize it. The next upgrading will also include an ATLAS detector upgrade. This work is devoted to the development of workflows of testing the silicon strip detectors used in the new ATLAS inner detector. The laser testing method was chosen for the needs of this work. In the first chapters of this work, the reader will learn about the principle of semiconductor detectors, their testing and use in ATLAS. The fourth chapter is devoted to the description of used equipment. The fifth chapter shows the results of the module testing. Discussion of measured results is devoted to chapter six. 1
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Study of the rare B-meson decays with the ATLAS experiment
Biroš, Marek ; Řezníček, Pavel (advisor) ; Scheirich, Daniel (referee)
Rare B0 d → K∗ µ− µ+ decay is one of physics channels testing Stan- dard Model predictions at the ATLAS experiment. This work provides input to the future analysis of this rare decay in the data-taking period of Run 2. Speci- fically, in the work we were searching for the descriptions of the distributions of reconstructed invariant masses of the B and K∗ mesons and of the distribution of the decay angles for the signal decay and expected background processes. For the procedure of finding optimal description, a maximal likelihood method of fit was used. Search for the probability density functions was performed on simulated data containing signal decay and main the background channels (decays, which are misinterpreted by the detector like our signal decay). The background decays included Bs → φ(K+ K− )µ+ µ− , Λb → Λ(1520)(pK− )µ+ µ− and Λb → pK− µ+ µ− . The signal data were contamined with events, when detector misidentified the kaon and pion from the K∗ meson decay, which lead to modifications of the fit- ted parameters. These cases were separated and treated as special background process. In addition to the simulations, we analyzed the combinatorial background from the real data of Run 1, though only the angular distribution. Invariant mas- ses were not analyzed for their simplicity. We also show...
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Studium rozpadů Higgsova bosonu na páry tau leptonů s použitím detektoru ATLAS na LHC
Kello, Tomáš ; Scheirich, Daniel (advisor) ; Řezníček, Pavel (referee)
The analysis of the Higgs boson decay into the pairs of tau leptons H → ττ is presented. In the scope of this thesis, only the tau leptons decaying purely lep- tonically are considered. This analysis is performed using data recorded from the proton-proton collisions at a center-of-mass energy √ s = 13 TeV by the ATLAS detector at the Large Hadron Collider and correspond to the integrated lumi- nosity of 36.1 fb−1 . The Boosted Decision Trees (BDT) multivariate technique was used in order to provide a classification of events. Datasets considered in this analysis consisted of the triggered, reconstructed and calibrated events. In addition, events had to pass the pre-selection criteria and were separated into four categories. Our main contribution to this analysis is based on developing and incorporating techniques used in the process of BDT training and evaluation. The performed analysis presented in this thesis is blinded. Therefore, the Monte Carlo simulation was used instead of real data in the Maximum Likelihood Fit in order to determine the expected significance. For the H → ττ leptonic channel, the expected signal significance was measured to be 1.16 σ. 1
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Rozbor současné úrovně a možnosti rozvoje organizačního a technologického zajištění těžební výroby u vybraných subjektů na Náchodsku
Řezníček, Pavel
This diploma thesis deal with evaluation of the current method of harvesting production on property of Společný les Peklo and Obecní lesy Olešnice v Orlických horách represented by motomanual harvesting and binding concentration of wood. As alternative to current mode, I chose harvesting production performed by harvestor node. In the theoretical part of work, harvesting-transporting process, basic construction parameters of harvestor technologies, the performance standards used in forestry management and also estates of interest are described. In the practical part, common comparison of technologies using SWOT analysis and performance standards including wage rate and practical comparison of technologies on specific property are performed.
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Tests of Semiconductor Detectors for ATLAS Upgrade
Theiner, Ondřej ; Kodyš, Peter (advisor) ; Řezníček, Pavel (referee)
Together with the planned upgrade of the Large Hadron Collider at CERN, a lot of experiments on the LHC will have to be improved as well. This is also the case of the ATLAS experiment. This thesis focuses on laser testing of silicon strip detectors which will be part of the Inner Tracker in the improved ATLAS Upgrade experiment. The first two parts of the thesis describe the ATLAS Up- grade experiment and summarise the basic theory behind silicon strip detectors. The third and the main part of the thesis is dedicated to experimental part of my work, which consisted of the actual laser testing of silicon strip detectors. The fourth chapter discusses the results of my measurements. All the tests presented in this thesis were performed in the laboratory of the Institute of Particle and Nuclear Physics in Prague. Besides having performed the measurements of de- tection properties of strip detectors, several ROOT macros for automatization of these measurements were written.
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