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Proton-Proton Interactions at the ATLAS Experiment at the LHC Accelerator
Přibyl, Lukáš ; Němeček, Stanislav (advisor) ; Soustružník, Karel (referee) ; Kupčo, Alexander (referee)
In this thesis the potential of the ATLAS detector to exclude or discover quark compositeness is studied in detail. There were four dierent sensitive analysis methods developed for this purpose. These methods use a detailed information about inclusive dijet pT-spectrum or dijet angular distribution and two of them use Bayesian technique (as is usual in similar analyses at Tevatron). For all four methods a larger number of systematic errors was taken into account and their inuence was studied in detail too. It is also shown, that the early data exclusion limit on quark compositeness reachable by the ATLAS experiment is + LL = 10.3 TeV at 95% C.L with 100 pb 1 of collision data of a sucient quality. This limit is considerably higher than the current limit known from Tevatron: + LL = 2.7 TeV at 95% C.L. The highest exclusion limit on quark compositeness with expected total amount of data to be collected by the ATLAS experiment is above 22 TeV, assuming 3% jet energy scale uncertainty.
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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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Study of azimuthal asymmetries in COMPASS Drell-Yan data
Pešková, Markéta ; Finger, Michael (advisor) ; Kupčo, Alexander (referee)
Title: Study of azimuthal asymmetries in COMPASS Drell-Yan data Author: Bc. Markéta Pešková Department / Institute: Department of Low Temperature Physics Supervisor of the master thesis: M.Sc. Michael Finger, CSc. Abstract: Drell-Yan (DY) process, i.e. a lepton pair production in hadron-hadron interaction, is one of the unique tools to study structure of hadrons. In this thesis we present its theoretical background and its link to description of the nucleon spin structure. The corresponding formalism of the Parton Distribution Functions (PDF) and the Transverse Momentum Dependent Parton Distribution Functions (TMD PDF) is explained in some detail. The fundamental theoretical prediction of a sign change of the T-odd TMDs in the DY and Semi- inclusive DIS (SIDIS) is described. In the following a concise description of the COMPASS apparatus is given with the emphasis on the setup modification needed and implemented for the Drell-Yan measurement performed in 2014 and 2015 with 190 GeV/c2 beam of negative pions and the proton target (polarised in 2015). In the final chapter we present our independent analysis of the DY data taken in 2015. Three azimuthal asymmetries giving access to the different TMD PDF were extracted using the dimuon events from a mass region of 4.3 to 8.5 GeV/c2 . Our results are in agreement...
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QCD and Diffraction in the ATLAS Experiment at the LHC
Kepka, Oldřich ; Kupčo, Alexander (advisor) ; Favart, Laurent (referee) ; Stirling, W.J. (referee)
This thesis is devoted to study the hard diffractive and exclusive events at the experiment ATLAS. Right after the start-up of a new proton accelerator LHC in CERN they will be identied using the rapidity gap method. We therefore developed an alternative denition of the observed energy in the ATLAS calorimeter to identify diffractive and exclusive events. During the high luminosity operation of the accelerator, forward detectors (AFP) recently proposed to be installed far from the interaction point approaching the beam at few millimeters will allow to tag the intact scattered protons in these events unambiguously. The simplest exclusive production is due to the exchange of two photons. We implemented twophoton exchanges in FPMC generator and analyzed the two-photon production of W and Z-pairs decaying leptonically to calculate sensitivities on triple and quartic anomalous gauge couplings of electroweak boson to photons. The obtained results are remarkable mainly for the quartic couplings. Their current limits can be improved by almost two orders of magnitude with early data and by four orders of magnitude using large luminosity and AFP detectors. In addition, we used two-photon dimuon events to determine the time needed to align one of the AFP stations with respect to beam to a desired precision. Another...
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Aspects of baryon and lepton number non-conservation in the Standard model of particle interactions and beyond
Hudec, Matěj ; Malinský, Michal (advisor) ; Kupčo, Alexander (referee) ; Nardecchia, Marco (referee)
This work is devoted to baryon and lepton number violation and flavour physics in theories beyond the Standard Model of particle interactions. First, the relations between the accidental and imposed symmetries are dis- cussed. For example, we argue that the Levi-Civita tensors in the color space may be understood as a unique spurion carrying the baryon number, and as such its absence in the Lagrangian of a specific model indicates baryon number conservation. Afterwards, the two minimal scenarios of quark-lepton unification are ana- lyzed in detail: the Minimal quark-lepton symmetry model and its extension by the inverse seesaw mechanism. We investigate if the observed anomalies in the B-meson decays could be to some extent accommodated within these models. Finally, possible low-energy effects of gauge leptoquarks are studied in the theory of quark-lepton unification and its simple extensions by vector-like leptons. Taking fully into account the freedom in the quark-lepton mixing, a catalogue of measurements currently forming the border of the excluded parameter space is found. We argue that, within the considered class of models, the gauge leptoquark can account for the discrepancies in the neutral-current B decays if and only if at least two extra generations of weak-isosinglet leptons exist. 1
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Study of azimuthal asymmetries in COMPASS Drell-Yan data
Pešková, Markéta ; Finger, Michael (advisor) ; Kupčo, Alexander (referee)
Title: Study of azimuthal asymmetries in COMPASS Drell-Yan data Author: Bc. Markéta Pešková Department / Institute: Department of Low Temperature Physics Supervisor of the master thesis: M.Sc. Michael Finger, CSc. Abstract: Drell-Yan (DY) process, i.e. a lepton pair production in hadron-hadron interaction, is one of the unique tools to study structure of hadrons. In this thesis we present its theoretical background and its link to description of the nucleon spin structure. The corresponding formalism of the Parton Distribution Functions (PDF) and the Transverse Momentum Dependent Parton Distribution Functions (TMD PDF) is explained in some detail. The fundamental theoretical prediction of a sign change of the T-odd TMDs in the DY and Semi- inclusive DIS (SIDIS) is described. In the following a concise description of the COMPASS apparatus is given with the emphasis on the setup modification needed and implemented for the Drell-Yan measurement performed in 2014 and 2015 with 190 GeV/c2 beam of negative pions and the proton target (polarised in 2015). In the final chapter we present our independent analysis of the DY data taken in 2015. Three azimuthal asymmetries giving access to the different TMD PDF were extracted using the dimuon events from a mass region of 4.3 to 8.5 GeV/c2 . Our results are in agreement...
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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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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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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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