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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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Top-Quark p(T)-Spectra at LHC and Flavor Independence of z-Scaling
Tokarev, M. V. ; Zborovský, Imrich
New results of analysis of top-quark differential cross sections obtained by the CMS and ATLAS Collaborations in pp collisions at the LHC in the framework of z-scaling approach are presented. The spectra are measured over a wide range of collision energy root s = 7, 8, 13 TeV and transverse momentum p(T) = 30-1000 GeV/c of top-quark using leptonic and jet decay modes. The LHC data on transverse momentum of the top-quark spectra are compared with the Tevatron data obtained by the Dempty set Collaboration in p (p) over bar collisions at root s = 1.96 GeV. Flavour independence of the scaling function psi(z) in pp and p (p) over bar interactions over a wide collision energy range root s = 19 - 13000 GeV is verified. This property of psi(z) was found for different hadrons from pi-meson up to. particle. The flavour independence of psi(z) is used as indication on self-similarity of to p-quark production. A tendency to saturation of psi(z) at low z for top-quark is demonstrated. We anticipate that data on low-and high-p(T) inclusive spectra of top-quark production at LHC energies could be of interest for verification of the self-similarity over a wide range of masses and different flavour content of produced particles.
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Measurement of the B0 meson lifetime at ATLAS detector
Řezníček, Pavel
Title: Measurement of the B0 d meson lifetime at ATLAS detector Author: Pavel Řezníček Department: Institute of Particle and Nuclear Physics Supervisor of the doctoral thesis: Dr. Zdeněk Doležal Supervisor's e-mail address: Zdenek.Dolezal@mff.cuni.cz Abstract: The lifetime of B0 d mesons is determined from their decays B0 d → J/ψK∗0 reconstructed in ATLAS experiment at the LHC using pp collision data at a center-of-mass energy of 7 TeV and corresponding to integrated luminosity of 40 pb−1 . The lifetime, extracted from the simultaneous unbinned maximum likelihood mass-lifetime fit, is 1.51±0.04 (stat.)±0.04 (syst.) ps. A total number of 2750±90 (stat.) signal B0 d decays are observed in the measurement, with a fit- ted B0 d mass of 5363.7 ± 1.2 (stat.) MeV. Both the extracted B0 d meson mass and lifetime are within the determined errors consistent with the world average values. Although the achieved precision is still significantly lower than the one of the world average value, the measurement successfully tested the feasibility of the fit-method and allowed to cross-check ATLAS detector performance. Keywords: CERN, LHC, ATLAS, B-physics, B-hadron, Lifetime
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Studium potlačení jetů ve srážkách těžkých iontů na LHC pomocí detektoru ATLAS
Štefko, Pavol ; Spousta, Martin (advisor) ; Pleskot, Vojtěch (referee)
Jet production in PbPb collisions at a per-nucleon center-of-mass energy of 2.76 TeV has been studied using the ATLAS detector at the LHC. Interactions between the high- pT partons and the hot, dense medium, produced in these ultrarelativistic collisions, are expected to cause the loss of the jet energy (jet quenching). This thesis presents results of the jet analysis done on the data taken during the 2011 heavy-ion run at the LHC. Jets are reconstructed using the anti-kt jet clustering algorithm and studied as a function of collision centrality and dijet energy imbalance. With increasing centrality, dijets are observed to be increasingly asymmetric, consistent with the theory of jet quenching. The study of charged particle tracks indicates the increase of the low-pT tracks in the strongly quenched jets. 1
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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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Measurement of the B0 meson lifetime at ATLAS detector
Řezníček, Pavel ; Doležal, Zdeněk (advisor) ; Cvach, Jaroslav (referee) ; Catmore, James Richard (referee)
Title: Measurement of the B0 d meson lifetime at ATLAS detector Author: Pavel Řezníček Department: Institute of Particle and Nuclear Physics Supervisor of the doctoral thesis: Dr. Zdeněk Doležal Supervisor's e-mail address: Zdenek.Dolezal@mff.cuni.cz Abstract: The lifetime of B0 d mesons is determined from their decays B0 d → J/ψK∗0 reconstructed in ATLAS experiment at the LHC using pp collision data at a center-of-mass energy of 7 TeV and corresponding to integrated luminosity of 40 pb−1 . The lifetime, extracted from the simultaneous unbinned maximum likelihood mass-lifetime fit, is 1.51±0.04 (stat.)±0.04 (syst.) ps. A total number of 2750±90 (stat.) signal B0 d decays are observed in the measurement, with a fit- ted B0 d mass of 5363.7 ± 1.2 (stat.) MeV. Both the extracted B0 d meson mass and lifetime are within the determined errors consistent with the world average values. Although the achieved precision is still significantly lower than the one of the world average value, the measurement successfully tested the feasibility of the fit-method and allowed to cross-check ATLAS detector performance. Keywords: CERN, LHC, ATLAS, B-physics, B-hadron, Lifetime
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Studium kanálu J/Psi + foton v proton-protonových srážkách pomocí detektoru ATLAS na LHC
Vidláková, Zuzana ; Vrba, Václav (advisor) ; Zálešák, Jaroslav (referee)
Title: Analysis of J/Psi + photon production in proton-proton collisions on ATLAS at LHC Author: Bc. Zuzana Vidláková Department: Institute of particle and nuclear physics Supervisor: prom. fyz. Václav Vrba, CSc. (Academy of Sciences of the Czech Republic) Abstract: The subject of this thesis is physics connected to quarkonia and their studies at the ATLAS detector situated at LHC in CERN, Geneva. In this thesis, following topics are cov- ered: ATLAS detector, history of physics connected to quarkonia, production mechanisms of quarkonia, software used at CERN for data analysis and cross-section measurement of J/Psi + photon continuum. The analysis was done on behalf of the B-physics working group at ATLAS. Keywords: CERN, LHC, ATLAS, B-fyzika, quarkonia
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Studium kinematiky rozpadů top-antitopových párů v experimentu Atlas
Berta, Peter ; Kvita, Jiří (advisor) ; Soustružník, Karel (referee)
In this thesis, I deal with the measurement of the transverse momentum spectrum of the top quark produced in top-antitop pairs at the LHC at center of mass energy 7 TeV. The analysis is carried out within the ATLAS collaboration. In the single lepton decay channel, I have performed studies on the simulation which were necessary to obtain the final spectrum from real data. I describe basic event selection rules to reduce background events. I study the efficiency of top-antitop pairs reconstruction. I study the unfolding of the measured spectrum which corrects for effects caused by imperfect resolutions. At the end, I show the measured top quark transverse momentum spectrum obtained from my analysis.
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Scaling features in high energy hadron and nucleus collisions
Zborovský, Imrich ; Tokarev, M. V.
Results of analysis of experimental data on inclusive cross sections of jets, direct photons, and high-pT hadrons produced in pp= ¯ pp and AA collisions are presented in the framework of zscaling. The data were obtained at ISR, S¯ppS, RHIC, and Tevatron. New properties of zpresentation of the inclusive spectra are discussed. A physical interpretation of the variable z and the scaling function y(z) is given. A microscopic scenario of hadron and nucleus collisions at a constituent level in terms of momentum fractions is developed. The z-scaling re ects the structure of the colliding objects, interaction of their constituents, and particle formation and manifests the general properties of self-similarity, locality, and fractality. The obtained results could be used for searching for new physics phenomena in high energy hadron and nucleus collisions in soft and hard regions at RHIC, Tevatron, and LHC.
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