Performance of the ATLAS Hadronic Endcap Calorimeter and the Physics of Electroweak Top Quark Production at ATLAS

The Large Hadron Collider (LHC) and the ATLAS experiment are currently under construction with first collisions expected in 2005. The performance of detector components built to the final ATLAS design specifications are evaluated in particle beams. In addition, detailed simulations are performed to estimate the sensitivity of the ATLAS experiment to various physical processes. This thesis is divided into two parts, with contributions to each of these types of performance studies. First, an analysis of the performance of the Hadronic Endcap Calorimeter (HEC) yields a pion energy resolution of s/E=78+/-2%/<rad><rcd>Eo( GeV)</rcd></rad> ⊕5.0+/-0.3% and an intrinsic electromagnetic to hadronic response ratio (e/h) of 1.6 +/- 0.1. Second, simulation studies have been performed to estimate the sensitivity of ATLAS to the measurement of Vtb and the polarization of the top quark from electroweak top production. Estimates from three independent channels yield statistical precisions of 0.5%, 2.2% and 2.8% after three years of low luminosity (1033cm-2s-1 ) LHC data-taking. The precision of the top polarization measurement from the highest rate electroweak channel is 1.6% after only 1 year of data- taking.