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Produkce jetů s velkou příčnou hybností na LHC
Podškubka, Radek ; Kupčo, Alexander (advisor) ; Lysák, Roman (referee)
In the first part of the thesis, theoretical uncertainties of jet cross-section have been calculated for proton-proton collision at the center of mass energy of 8 TeV. For jet identification the anti-kT algorithm with scale parameter R = 0.6 was used. As the calculations showed, the major contribution to the total theoretical uncertainty comes from the uncertainty of parton distribution function parameters. In the second part of the thesis, the angular distribution of dijet events produced in proton-proton collisions at the center of mass energy 8 TeV were simulated using Pythia 8 Monte Carlo event generator. New physics model of quark compositeness that should manifest itself by quark contact interaction was studied using angular distribution of dijet events. Three angular variables were discussed and these variables were used to calculate 95% CL lower limit on contact interaction scale. The results were compared and it emerged that the sensitivity to contact interaction signals varies for these variables.
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Search for Axion-Like Particles at the NA62 experiment
Jerhot, Jan ; Kampf, Karol (advisor) ; Hořejší, Jiří (referee)
The thesis instructively presents axions and axion-like particles as a plau- sible extension of the Standard Model of particle physics and discusses also the cosmological implications in the case of their existence as they present one of the most favourable dark matter candidates at given circumstances. The main part of the thesis is concerned with a search for axion-like particles at the NA62 experiment at CERN and a study of the gathered data and its impact on the data analysis.
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Search for Axion-Like Particles at the NA62 experiment
Jerhot, Jan ; Kampf, Karol (advisor) ; Hořejší, Jiří (referee)
The thesis instructively presents axions and axion-like particles as a plau- sible extension of the Standard Model of particle physics and discusses also the cosmological implications in the case of their existence as they present one of the most favourable dark matter candidates at given circumstances. The main part of the thesis is concerned with a search for axion-like particles at the NA62 experiment at CERN and a study of the gathered data and its impact on the data analysis.
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Produkce jetů s velkou příčnou hybností na LHC
Podškubka, Radek ; Kupčo, Alexander (advisor) ; Lysák, Roman (referee)
In the first part of the thesis, theoretical uncertainties of jet cross-section have been calculated for proton-proton collision at the center of mass energy of 8 TeV. For jet identification the anti-kT algorithm with scale parameter R = 0.6 was used. As the calculations showed, the major contribution to the total theoretical uncertainty comes from the uncertainty of parton distribution function parameters. In the second part of the thesis, the angular distribution of dijet events produced in proton-proton collisions at the center of mass energy 8 TeV were simulated using Pythia 8 Monte Carlo event generator. New physics model of quark compositeness that should manifest itself by quark contact interaction was studied using angular distribution of dijet events. Three angular variables were discussed and these variables were used to calculate 95% CL lower limit on contact interaction scale. The results were compared and it emerged that the sensitivity to contact interaction signals varies for these variables.
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Measurement of the inclusive jet cross-section with the ATLAS detector
Pleskot, Vojtěch ; Davídek, Tomáš (advisor) ; Starovoitov, Pavel (referee) ; Taševský, Marek (referee)
The Large Hadron Collider is an accelerator based in the European Organization for Nuclear Research (CERN). It accelerates protons to the highest energies ever reached by the mankind. The ATLAS experiment records data from the proton-proton collisions. Common objects born in the collisions are jets, i.e. collimated bursts of hadrons. This thesis presents the newest ATLAS measurement of the inclusive jet cross-section. The data sample used was recorded in 2011 at 7 TeV centre-of-mass energy. Calorimeter is the most important part of ATLAS for the jet reconstruction. During the data taking, the hadronic calorimeter faced several failures of its components, modules. These non-operating parts have important impact on the jet energy measurement. The thesis describes tests of two available software corrections of the affected jet energies. 1
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Measurement of Diffractive Dijet Production in Deep Inelastic Scattering at HERA Collider
Pokorný, Boris ; Valkárová, Alice (advisor) ; Kupčo, Alexander (referee) ; Leitner, Rupert (referee)
The diffractive production of two jets in deep inelastic e± p scattering is mea- sured in the kinematic region of photon virtuality 4 < Q2 < 80 GeV2 , inelasticity 0.1 < y < 0.7, momentum fraction xIP < 0.03, proton ver- tex momentum transfer |t| < 1 and mass of a dissociative baryonic system MY < 1.6 GeV. Diffractive events are identified with the large rapidity gap technique. Integrated and single differential cross sections are measured for jets of transverse momenta p∗ T1 > 5.5 GeV and p∗ T2 > 4.0 GeV and pseudora- pidities −3 < η∗ 1,2 < 0. The data were collected by the H1 experiment at the HERA collider in years 2005-2007, corresponding to an integrated luminosity of 283.7 pb−1 . The measurements are compared with NLO predictions based on the DGLAP parton evolution.
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Partonic showers and jets
Hladík, Ondřej ; Kupčo, Alexander (advisor) ; Spousta, Martin (referee)
Title: Partonic showers and jets Author: Ondřej Hladík Department: Institute of Theoretical Physics MFF UK Supervisor: Mgr. Alexander Kupčo, Ph.D., Institute of Physics ASCR, v. v. i. Abstract: In the present thesis we compare experimentally measured differential and integrated jets shapes with predictions of quantum chromodynamics (QCD) at the second order (NLO) of perturbative expansion. The measured jet sha- pes were taken from ATLAS experiment at LHC in proton-proton collisions at a center-of-mass energy √ s = 7 TeV and were compared with these predictions. The jets were reconstructed by means of anti-kT jet algorithm with R = 0.6. The predictions at NLO QCD agree with data in wider kinematics region than predictions at leading order (LO). The agreement, however, is still in some kine- matical regions not satisfactory. Keywords: QCD, jets, jet shapes, LHC
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Investigation of the factorization scheme dependence of finite order perturbative QCD calculations
Kolář, Karel ; Chýla, Jiří (advisor) ; Rameš, Jiří (referee) ; Formánek, Jiří (referee)
Title: Investigation of the factorization scheme dependence of finite order per- turbative QCD calculations Author: Karel Kolář Institute: Institute of Particle and Nuclear Physics Supervisor of the doctoral thesis: prof. Jiří Chýla, CSc., Institute of Physics of the Academy of Sciences of the Czech Republic Abstract: The main aim of this thesis is the investigation of phenomenological implications of the freedom in the choice of the factorization scheme for the de- scription of hard collisions with the potential application for an improvement of current NLO Monte Carlo event generators. We analyze the freedom associated with the definition of parton distribution functions and we derive general formu- lae governing the dependence of parton distribution functions and hard scattering cross-sections on unphysical quantities specifying the renormalization and factor- ization procedure. The issue of the specification of factorization schemes via the corresponding higher order splitting functions is discussed in detail. The main attention is paid to the so called ZERO factorization scheme, which allows the construction of consistent NLO Monte Carlo event generators in which initial state parton showers can be taken formally at the LO. Unfortunately, it has turned out that the practical applicability of the ZERO...
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Analysis of dijet events in diffractive ep interactions with tagged leading proton at the H1 experiment
Polifka, Richard ; Valkárová, Alice (advisor) ; Taševský, Marek (referee) ; Newman, Paul (referee)
Title: Analysis of dijet events in diffractive ep interactions with tagged leading proton at the H1 experiment Author: Richard Polifka Department: Institute of Particle and Nuclear Physics Supervisor: RNDr. Alice Valkárová, DrSc. Supervisor's e-mail address: avalkar@mail.desy.de Abstract: An inclusive dijet production in diffractive deep-inelastic scattering is measured. The diffractive selection is based on tagging of the leading proton in the Forward Proton Spectrometer. The statistics of events obtained during the HERA II running period (integrated luminosity of 156.7 pb−1 ) enables the measurement of jet final states with leading proton for the first time. The data cover the phase space of xIP < 0.1, |t| <= 1.0 GeV2 and 4 <= Q2 <= 110 GeV2 . The dijet data are compared with the next to leading order predictions of the quantum chromodynamics (QCD). The phase space of diffractive dijets is in this analysis by factor of 3 in xIP larger than in previous measurements. The QCD predictions based on the DGLAP parton evolution describe the measured data well even in a non-DGLAP enriched phase space where one on the jets goes into the region close to the direction of the outgoing proton. The measured single-differential cross sections are compared to several Monte Carlo models with different treatment of...
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