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Zkoumání vlastností Higgsova bosonu v experimentu ATLAS
Mlynáriková, Michaela ; Leitner, Rupert (advisor) ; Kampf, Karol (referee)
The Standard Model of elementary particles (SM) predicts the existence of a neutral scalar Higgs boson. However, there are also extensions of the SM (such as the MSSM) in which a number of Higgs bosons is predicted. Especially the additional presence of pseudoscalar and charged Higgs bosons represents one of the crucial differences between the SM and its exten- sions. This work develops a method for determination of the spin and parity of the Higgs boson in several H → ττ decays, namely: H→ τ+ τ− → (h+ ντ )(h− ¯ντ ), H→ τ+ τ− → ( + ντ ¯ν )(π− ¯ντ ) and H→ τ+ τ− → ( + ντ ¯ν )( − ¯ντ ν ), where h denotes π or ρ meson. The method is based on the angular and energy correlations of charged final products from the decays mentioned above. Additionally, the work studies the possibility of signal (Higgs boson decay) and background (Z → ττ decay) discrimination, when one considers a decaying boson with spin 1. All calcula- tions are done in the leading order of perturbation theory. 1
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Úhlové korelace v rozpadech Higgsova bosonu
Pleskot, Vojtěch ; Davídek, Tomáš (advisor) ; Dolejší, Jiří (referee)
The Standard Model predicts existence of one Higgs boson with combined parity CP = +1. In MSSM there exist Higgs boson with CP = −1 in addition. The work develops one method of Higgs boson CP determination on the basis of angular correlations of pions and ρ-mesons born in cascade decay H/A → τ− τ+ → ρ− /π− ντ ρ+ /π+ ¯ντ . The calculations are done in the leading order of perturbation theory. Further, the possibility of signal (Higgs boson decay) and background (Z boson decay) differentiation is studied. The processes in question are simulated using Monte Carlo generators Pythia and Tauola. Simulation outputs are compared with calculated theoretical results. 1
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Cross-section measurements of the Higgs boson decaying into a pair of tau leptons with the ATLAS detector
Mlynáriková, Michaela ; Davídek, Tomáš (advisor) ; Hubáček, Zdeněk (referee) ; Šumbera, Michal (referee)
The ATLAS experiment is one of the two general-purpose detectors at the Large Hadron Collider (LHC) at the European Organisation for Nuclear Research (CERN) in Switzerland. ATLAS is designed for precision mea- surements of particle properties, the search of the Higgs boson and new physics beyond the Standard Model. The experiment got worldwide atten- tion in 2012, when after the collaborative efforts with the CMS experiment the Higgs boson discovery was announced. After the discovery, the preci- sion measurements of its properties became one of the main objectives of the LHC physics programme, since a potential observation of deviations from the Standard Model predictions might lead to the discovery of new physics. In this thesis, the measurements of the Higgs boson production cross-sections in the H → ττ decay channel are presented. Based on the proton-proton collision data collected at the centre-of-mass energy of 13 TeV in years 2015 and 2016, the signal over the expected background from the other Standard Model processes is established with the observed significance of 4.4σ. Com- bined with the data collected at 7 and 8 TeV, the observed signal significance amounts to 6.4σ, which constitutes a single experiment observation of the H → ττ decays by ATLAS. All presented results are found to be consistent with...
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Reconstruction of the Higgs boson decay into two photons for Future Circular Collider (FCC)
Petrů, Tadeáš ; Faltová, Jana (advisor) ; Petukhova, Krystsina (referee)
It is now high time to plan projects at the CERN laboratory for the time after the physics programme of the HL-LHC collider is over. One of the option is a nearly 100 km long collider with centre-of-mass energies up to 100 TeV in Geneva area - Future Circular Collider (FCC). A proton-proton collider called FCC-hh is the main part of the project. The design of the detector for the FCC-hh experiment is one of the challenges. Our group is involved in the studies of the electromagnetic calorimeter for this project. The student will learn the concept of the proposed calorimeter. The goal of the thesis is a reconstruction of the Higgs boson decay into two photons and a study of the influence of the coincident collisions on the Higgs boson mass peak resolution. 1
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Reconstruction of the Higgs boson decay into two photons for Future Circular Collider (FCC)
Petrů, Tadeáš ; Faltová, Jana (advisor) ; Petukhova, Krystsina (referee)
It is now high time to plan projects at the CERN laboratory for the time after the physics programme of the HL-LHC collider is over. One of the option is a nearly 100 km long collider with centre-of-mass energies up to 100 TeV in Geneva area - Future Circular Collider (FCC). A proton-proton collider called FCC-hh is the main part of the project. The design of the detector for the FCC-hh experiment is one of the challenges. Our group is involved in the studies of the electromagnetic calorimeter for this project. The student will learn the concept of the proposed calorimeter. The goal of the thesis is a reconstruction of the Higgs boson decay into two photons and a study of the influence of the coincident collisions on the Higgs boson mass peak resolution. 1
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Cross-section measurements of the Higgs boson decaying into a pair of tau leptons with the ATLAS detector
Mlynáriková, Michaela ; Davídek, Tomáš (advisor) ; Hubáček, Zdeněk (referee) ; Šumbera, Michal (referee)
The ATLAS experiment is one of the two general-purpose detectors at the Large Hadron Collider (LHC) at the European Organisation for Nuclear Research (CERN) in Switzerland. ATLAS is designed for precision mea- surements of particle properties, the search of the Higgs boson and new physics beyond the Standard Model. The experiment got worldwide atten- tion in 2012, when after the collaborative efforts with the CMS experiment the Higgs boson discovery was announced. After the discovery, the preci- sion measurements of its properties became one of the main objectives of the LHC physics programme, since a potential observation of deviations from the Standard Model predictions might lead to the discovery of new physics. In this thesis, the measurements of the Higgs boson production cross-sections in the H → ττ decay channel are presented. Based on the proton-proton collision data collected at the centre-of-mass energy of 13 TeV in years 2015 and 2016, the signal over the expected background from the other Standard Model processes is established with the observed significance of 4.4σ. Com- bined with the data collected at 7 and 8 TeV, the observed signal significance amounts to 6.4σ, which constitutes a single experiment observation of the H → ττ decays by ATLAS. All presented results are found to be consistent with...
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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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Study of the lepton flavor violating decays of the Higgs boson at the ATLAS experiment
Kouba, Petr ; Scheirich, Daniel (advisor) ; Mlynáriková, Michaela (referee)
Title: Study of the Lepton Flavor Violating Decays of the Higgs Boson at the ATLAS Experiment Author: Petr Kouba Institute: Institute of Particle and Nuclear Physics Supervisor: Mgr. Daniel Scheirich, Ph.D., Institute of Particle and Nuclear Physics Abstract: The thesis contains an analysis of the potential lepton flavor violating Higgs boson decays performed on the data acquired by the ATLAS experiment during the Run II period of the LHC. The analysis comprised of an event selection aiming at the reduction of the backgrounds, while keeping the highest possible amount of the signal events. An estimate of the leptons misidentified by the reconstruction algorithms of the ATLAS experiment was included in the anal- ysis. For the selected events, invariant mass was reconstructed in the collinear approximation. The distribution of the invariant mass according to the MMC was provided for reference purposes. Keywords: Higgs boson, ATLAS, collinear approximation ii
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Zkoumání vlastností Higgsova bosonu v experimentu ATLAS
Mlynáriková, Michaela ; Leitner, Rupert (advisor) ; Kampf, Karol (referee)
The Standard Model of elementary particles (SM) predicts the existence of a neutral scalar Higgs boson. However, there are also extensions of the SM (such as the MSSM) in which a number of Higgs bosons is predicted. Especially the additional presence of pseudoscalar and charged Higgs bosons represents one of the crucial differences between the SM and its exten- sions. This work develops a method for determination of the spin and parity of the Higgs boson in several H → ττ decays, namely: H→ τ+ τ− → (h+ ντ )(h− ¯ντ ), H→ τ+ τ− → ( + ντ ¯ν )(π− ¯ντ ) and H→ τ+ τ− → ( + ντ ¯ν )( − ¯ντ ν ), where h denotes π or ρ meson. The method is based on the angular and energy correlations of charged final products from the decays mentioned above. Additionally, the work studies the possibility of signal (Higgs boson decay) and background (Z → ττ decay) discrimination, when one considers a decaying boson with spin 1. All calcula- tions are done in the leading order of perturbation theory. 1
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Úhlové korelace v rozpadech Higgsova bosonu
Pleskot, Vojtěch ; Davídek, Tomáš (advisor) ; Dolejší, Jiří (referee)
The Standard Model predicts existence of one Higgs boson with combined parity CP = +1. In MSSM there exist Higgs boson with CP = −1 in addition. The work develops one method of Higgs boson CP determination on the basis of angular correlations of pions and ρ-mesons born in cascade decay H/A → τ− τ+ → ρ− /π− ντ ρ+ /π+ ¯ντ . The calculations are done in the leading order of perturbation theory. Further, the possibility of signal (Higgs boson decay) and background (Z boson decay) differentiation is studied. The processes in question are simulated using Monte Carlo generators Pythia and Tauola. Simulation outputs are compared with calculated theoretical results. 1
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