No description available.

There is strong motivation to study standard model physics using the highest-energy data provided by the Large Hadron Collider. This is aided by the process of defining clusters of hadrons to form ‘jets’. Existing jet-finders are dependent on pre-defined parameters which, to some extent, influence their properties. This thesis introduces a novel algorithm which aims to reconstruct partons outgoing from hard interactions, prior to any splitting, by concentrating solely on the highest momentum transfer scale. In this way parton properties such as fragmentation and structure functions from hadron colliders may be compared directly with results from DIS and e+e− annihilation. This original, standalone tool is named ‘traps’ - the Topological Reconstruction Algorithm for Parton Scatters. The algorithm was developed using Pythia Monte Carlo QCD events, under a pragmatic approach that assumes the model provides a good approximation to reality at both hadronic and partonic level. Various tests were made to gauge the performance of the algorithm against standard jet-finders. The infrared safety and algorithm speed were also assessed. The objective of traps is to have low sensitivity to parameters, and to be fast and robust. A high event acceptance is necessary, as maximum statistics are required where cross-sections are at their lowest. A chapter of this thesis is dedicated to a description of the author’s studies in calibration and monitoring of the timing of the ATLAS Level-1 Calorimeter Trigger system. Pulses from triggered energy are sent via largely η× φ = 0.1 × 0.1 granularity ‘trigger towers’. Synchronous triggering with 1-2 ns precision is required for the system to make an accurate energy estimate.

Graduate

Thesis (Ph. D.)--Florida State University, 2005. / Advisor: Dr. Laura Reina, Florida State University, College of Arts and Sciences, Dept. of Physics. Title and description from dissertation home page (viewed Sept. 14, 2005). Document formatted into pages; contains xv, 212 pages. Includes bibliographical references.

The low mass Drell-Yan di-muon process is investigated with the ATLAS detector at the LHC, in order to provide information that advances our knowledge of the Parton Density Functions in a region of phase space unaccessible at previous experiments. A cut-based selection of di-muon events is performed, using 2010 data with a centre of mass energy of the proton-proton collisions of 7TeV, and an integrated luminosity of 36 pb−1. The analysis probes the region of low muon transverse momentum (pT > 6GeV), and low di-muon mass region 12 < M < 66GeV. The main challenges of the analysis are the understanding of the muon isolation and the trigger efficiency. In order to reject the large QCD background the analysis relies on stringent isolation criteria. The efficiency of the chosen selection is presented in detail. The second main part of the analysis is the measurement of the trigger efficiency for low pT threshold muon triggers. This is an important aspect of the cross section measurement, since the pT spectrum of leptons from the low mass Drell-Yan process are soft and populate the trigger threshold region. In order to measure the differential cross section in mass d dM in the fiducial region of |η| < 2.4 and pT,μ1 > 9GeV and pT,μ2 > 6GeV (asymmetric analysis) or pT,μ1 > 6GeV and pT,μ2 > 6GeV (symmetric analysis), a one dimensional bin-by-bin unfolding is adopted to account for detector reconstruction and resolution effects; all the associated uncertainties are also presented. The fiducial and extrapolated differential cross sections are measured at the Born level. Dressed level corrections are also given. The measured cross sections are shown to agree with theoretical predictions within the margin of error. A precision of 9.7% is achieved in the asymmetric analysis in the lowest invariant mass bin between 12 and 17GeV; the statistical and systematic uncertainties in the same bin are 4.2% and 8.7% respectively. In the remaining mass region the total uncertainty is smaller. The luminosity error during the 2010 data taking period is estimated to be 3.4%. In addition to the Drell-Yan cross section measurement, the thesis describes the study performed in order to extract the Lorentz angle value in the ATLAS Semiconductor Tracker. The Lorentz angle is computed through the study of the SCT cluster width from both cosmic and collision data and comparison with simulation is shown. The track selection on collision data is defined and the fitting range is optimised to give robust results. Throughout this thesis the convention c = 1 is adopted.

Thesis (Ph. D.)--University of Iowa, 2003. / Supervisor: Yasar Onel. Includes bibliographical references (leaves 154-164).

No description available.

Any future linear collider requires a beam stabilisation system at the interaction point to the to maintain luminosities. This thesis details the development of prototypes of three such systems based at the Accelerator Test Facility 2 (ATF2) at KEK, Japan. The upstream feedback system utilises two stripline beam position monitors (BPMs) and two stripline kickers located in the ATF2 extraction line to stabilise the position and angle of the beam; the correction is then measured downstream at the ATF2 beam waist by a cavity BPM. The feedforward system uses the two upstream stripline BPMs to measure the position of the beam and calculate a correction signal which is then implemented locally by a stripline kicker located near the beam waist; the correction is then measured at the beam waist by a cavity BPM. The IP feedback system uses the position measured at the ATF2 beam waist by a cavity BPM and implements a correction based on this position using the local stripline kicker; the correction is then measured at the beam waist by a cavity BPM. Tests of the upstream feedback system have demonstrated stabilisation of the ATF2 beam waist at approximately the 300 nm level; tests of the feedforward and IP feedback systems have demonstrated stabilisation of the ATF2 beam waist at approximately the 100 nm level. Additional work undertaken to improve the processing electronics of the stripline BPMs is detailed. The cavity BPMs and their electronics are characterised and offline analysis techniques to improve the BPM resolutions set out. Results demonstrating resolutions of approximately 350 nm for the stripline BPMs and 80 nm for the cavity BPMs are presented.

Thesis (Ph. D.)--Florida State University, 2002. / Advisor: Dr. Horst Wahl, Florida State University, College of Arts and Sciences, Dept. of Physics. Title and description from dissertation home page (Oct. 6, 2003). Includes bibliographical references.

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