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).

Thesis presented in fulfilment of the requirements for the degree of Master of Science in Physics at the University of the Witwatersrand School of Physics, University of the Witwatersrand, 2015. / A search for the pseudoscalar A boson, which is predicted by in many models with an extended Higgs sector, gives a gateway to searches for physics beyond the Standard Model (SM). This thesis presents the results of a search for gluon-fusion produced A in the decay to Zh, with a final state of two electrons or muons and two τ leptons, in 20.3 fb−1of proton-proton collision data at √s = 8 TeV. Each tau lepton is allowed to dacay either leptonically, τlep, or hadronically,τhad, giving rise to three final states, τlepτlep, τlepτhad and τhadτhad. Focus is placed on the methodology and results of the fully hadronic channel. No evidence for the existence of an A boson is found in the scanned range of 220 ≤ mA ≤ 1000 GeV and 95% CL upper limits are placed on the gluon-fusion cross section times branching ratio, σ × BR(A → Zh) × BR(h → ℓℓττ). The results are combined with a complementing A → Zh search, where h → b¯b, and interpreted in view of two-Higgs-Doublet-Models (2HDMs), where exclusion limits are placed on large sections of phasepace.

No description available.

In preparations for the ATLAS experiment at the Large Hadron Collider at CERN, sections of the ATLAS Electromagnetic Endcap Calorimeter (EMEC) and Hadronic Endcap Calorimeter (HEC) were subjected to particle beams in the summer of 2002. The EMEC and HEC are non-compensating calorimeters with e/h > I: electromag¬netic showers will, on average; have a higher energy response than hadronic showers initiated by particles of the same energy. To reconstruct the energy of pions, the method of software compensation is investigated. Several beam energy dependent weighting schemes are studied, using calorimeter depth weights and cluster energy density weights. Finally, a beam energy independent cluster energy density weighting scheme is studied. Partial software compensation is achieved for pion energy recon¬struction, improving the energy resolution and response linearity of the calorimeters.

In preparation for the ATLAS experiment at the LHC at CERN. the high pseudorapidity region (|n| > 2.5) of the ATLAS end-cap liquid argon calorimeters underwent particle beam testing in 2004. One of the main goals of these tests is to study energy reconstruction in the complex interface region between the electromagnetic. hadronic, and forward calorimeters at. 1 - 3.2. These detectors were exposed to beams of electrons and pions with energies ranging from 6 GeV to 200 GeV. Three methods of calibration in the electromagnetic end-cap calorimeter (EMEC) are studied and compared to the results of a previous beam test. of the EMEC. The electromagnetic scale factor (aEM) is computed and compared to the previous beam test value. Studies of the energy response and resolution of the high pseudorapidity region of the three end-cap calorimeters to the particle beam position scans are given.

The HERA accelerator, an electron-proton collider facility based at the DESY laboratory in Hamburg, started delivering luminosity to the ZEUS experiment in May 1992. The short time of 96ns between bunch crossings and the fact that the primary source of detector activity in ZEUS does not come from the e-p interactions of interest but rather from other sources makes a high performance three level trigger system essential to data-taking. We present one part of the ZEUS trigger system, the Central Tracking Detector First Level Trigger (CTD-FLT). The principle of operation and the hardware implementation are discussed at length. A prototype system which was used during the early stages of ZEUS data-taking is described. We detail the principles of the CTD-FLT hardware testing and discuss aspects of the First Level Trigger data from the 1993 running period. During this time the CTD trigger has proved to be an invaluable part of the overall system. The high energies accessible at HERA make it possible to probe a variety of new physics models. The second part of this thesis focuses on one such model - Supersymmetry (SUSY). After an introduction to the model, a search for R-parity violating SUSY in the ZEUS data from the 1992 running period is described. No evidence for such signals has been found and hence we set upper limits on the mass scale of the theory. Finally we present a Monte Carlo study of the potential discovery reach of HERA for R-parity violating SUSY models, and come to the conclusion that HERA is an ideal place to look for such phenomena.