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Elastic Scattering at the LHC
Kašpar, Jan ; Kundrát, Vojtěch (advisor) ; Valkárová, Alice (referee) ; Kupčo, Alexander (referee)
Title: Elastic scattering at the LHC Author: Jan Kasˇpar Departement: Institute of Particle and Nuclear Physics Supervisor of the thesis: RNDr. Vojtečh Kundra't, DrSc., Institute of Physics AS CR Abstract: The seemingly simple elastic scattering of protons still presents a challenge for the theory. In this thesis we discuss the elastic scattering from theoretical as well as experimental point of view. In the theory part, we present several mod- els and their predictions for the LHC. We also discuss the Coulomb-hadronic interference, where we present a new eikonal calculation to all orders of α, the fine-structure constant. In the experimental part we introduce the TOTEM experiment which is dedicated, among other subjects, to the measurement of the elastic scattering at the LHC. This measurement is performed primarily with the Roman Pot (RP) detectors - movable beam-pipe insertions hundreds of meters from the interaction point, that can detect protons scattered to very small angles. We discuss some aspects of the RP simulation and reconstruc- tion software. A central point is devoted to the techniques of RP alignment - determining the RP sensor positions relative to each other and to the beam. At the end we present the analysis of TOTEM's first elastic scattering mea- surement at the LHC. The resulting...
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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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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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The QCD analysis of multijet events in proton-antiproton collisions at the Tevatron
Kepka, Oldřich ; Kupčo, Alexander (advisor) ; Žáček, Josef (referee)
The recent developments in theoretical calculations (code NLOJET++) allow us to evaluate the 3-jet observables at the next-to-leading order precision. In this diploma thesis we investigate the potential of using 3-jet observables for the measurement of strong coupling s at hadron colliders. First, we analyze the inclusive jet cross section measured by DO Collaboration, determine s and demonstrate its running in a similar way as was previously done by CDF Collaboration. In the second part of the thesis, we analyze the DO measurement of dijet azimuthal decorrelations. With this choice of 3-jet observable we were able to achieve a better precision of s than in the previous s measurements based on the inclusive jet production.
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