Search for Physics beyond the Standard Model with the ATLAS detector and the development of radiation detectors

We are investigating a radiation detector based on plasma display panel technology, the principal component of plasma television displays. This Plasma Panel Sensor (PPS) technology is a variant of micro-pattern gas radiation detectors. Based on the properties of existing plasma display panels, we expect eventually to be able to build a sealed array of plasma discharge gas cells to detect ionizing radiation with fast rise time of less than 10ns and high spatial resolution using a pixel pitch of less than 100 micrometer. In this thesis I shall describe our program of testing plasma display panels as detectors, including simulations, design and the first laboratory and beam studies that demonstrate the detection of cosmic ray muons, beta rays and medium energy protons. The ATLAS detector is used to search for high-mass resonances, in particular heavy neutral gauge bosons (Z') and excited states of Kaluza-Klein γ/Z bosons decaying to an electron-positron pair or a muon-antimuon pair. Results are presented based on the analysis of pp collisions at a center-of-mass energy of 7 TeV and 8 TeV at the LHC. These results corresponds to an integrated luminosity of 4.9 (e+e-) / 5.9 (μ−μ+) /fb and the 5.9 (e+e-) / 6 (μ−μ+) /fb collected by the ATLAS experiment in 2011 and 2012 respectively. In both the 2011 and 2012 analyses no deviation from the Standard Model (SM) were found. In the 2011 analysis the Kaluza-Klein γ/Z bosons were excluded at 95% confidence level (CL) for masses below 4.03 TeV in the electronic channel and below 4.71 TeV when the muon channel is included. A Z' with SM couplings is excluded at 95% CL for masses below 2.08 TeV in the electron channel and 2.22 TeV when the muon channel is included. In the 2012 analysis the exclusion of the Z′ with SM coupling was extended, so that with 95% CL the model is excluded for masses below 2.39 TeV in the electron channel and 2.49 TeV when the muon channel is included. The results were also interpreted in a Grand Unification model based on the E6 gauge group.