Doctor of Philosophy / Department of Physics / Glenn Horton-Smith / Double Chooz is a reactor neutrino experiment which has shown evidence of electron anti-neutrino disappearance at 1 km distance. It has been able to exclude the no-oscillation hypothesis at 99.8% CL (2.9ς) with only one detector. From a rate plus spectral shape analysis, the value of sin²2θ₁₃ was found to be 0.109±0.030(stat) ± 0.025(syst). Correlated events mimicking an anti-neutrino event are one of the most important backgrounds for a reactor neutrino experiment like Double Chooz which measured the neutrino mixing angle θ₁₃. Cosmic muons passing through the rock surrounding the detector produce fast neutrons which give rise to correlated events through proton recoil followed by a neutron capture. Muons stopping around the chimney region subsequently decay into Michel electrons also contributing to the correlated background. Measurement of the shape and rate of this background is very important for the precise measurement of θ₁₃. Experimental techniques to estimate of the shape and rate of this background in the Double Chooz far detector are presented in this thesis.

Doctor of Philosophy / Department of Physics / Glenn Horton-Smith / In March 2012, the Double Chooz reactor neutrino experiment published its most precise result so far: sin[superscript]2 2theta13 = 0.109 +/- 0.030(stat.) +/- 0.025(syst.). The statistical significance is 99.8% away from the no-oscillation hypothesis. The systematic uncertainties from background and detection efficiency are smaller than the first publication of the Double Chooz experiment. The neutron detection efficiency, one of the biggest contributions in detection systematic uncertainties, is a primary topic of this dissertation. The neutron detection efficiency is the product of three factors: the Gd-capture fraction, the efficiency of time difference between prompt and delayed signals, and the efficiency of energy containment. [superscript]252 Cf is used to determine the three factors in this study. The neutron detection efficiency from the [superscript]252 Cf result is confirmed by the electron antineutrino data and Monte Carlo simulations. The systematic uncertainty from the neutron detection efficiency is 0.91% used in the sin[superscript]2 2theta13 analysis. The seasonal variation in detector performance and the seasonal variations of the muon intensity are described in detail as well. The detector stability is confirmed by observation of two phenomena: 1) the [electron antineutrino] rate, which is seen to be uncorrelated with the liquid scintillator temperature, and 2) the daily muon rate, which has the expected correspondence with the effective atmospheric temperature. The correlation between the muon rate and effective atmospheric temperature is further analyzed in this thesis to determine the ratio of kaon to pion in the local atmosphere. An upper limit on instability of the neutron detection efficiency is established in the final chapter. The systematic error, 0.13%, from the relative instability is the deviation of the calibration runs. This thesis concludes with the potential systematic errors of neutron detection efficiency and estimation of how these potential systematic errors affect the result of sin[superscript]2 2theta13.

Doctor of Philosophy / Physics / Andrew G. Ivanov / In this thesis the measurement of production cross section of top-quark pairs in association with a photon in proton-proton collisions at a center of mass energy of 8 TeV is presented. The data was recorded at the CMS experiment at the LHC in 2012. This measurement aims to extend our knowledge of top quark properties and help to test consistency of the Standard Model (SM) of particle physics. Data-driven methods are used to estimate the photon identification efficiency and purity. The measured cross-section agrees with the standard model expectation.

Doctor of Philosophy / Department of Physics / Yurii Maravin / In this dissertation, you will find a study of di-boson production in pp collision with the Compact Muon Solenoid (CMS) detector at Large Hadron Collider (LHC). A study of Z+gamma process is performed on the data collected by the CMS during 2011 and corresponding to integrated luminosity L= 5 fb[superscript]-1. The study consists of two parts: cross section measurement and setting the limits on anomalous trilinear gauge couplings (aTGC) between a Z boson and a photon. The measured cross-section of Z+gamma agrees within the uncertainties with the standard model predicted cross section at next to leading order. Having found no excess in cross section measurement, we set the 95% con fidence level (C.L.) limit on aTGC. Another study discussed is a study of a low-scale walking Technicolor model with rho[subscript]T and a[subscript]T production in the fully leptonic fi nal state at 95% C.L. in proton-proton collisions at center of mass energy 10 TeV scenario using Monte Carlo simulation. We conclude that such processes can be excluded with 366 pb[superscript]-1 of data for rho[superscript]T masses up to 400 GeV and the observation would require 2.8 fb[superscript]-1 of data with 5 sigma precision.

Doctor of Philosophy / Department of Physics / Tim Bolton / This thesis represents the first study of the helicity distributions of Z[gamma] di-boson production at hadron colliders. I use 5 fb⁻¹ of [radical]s = 7 TeV center of mass energy proton-proton collision data, collected by the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC), to look at the angular distribution of the Z[gamma] [right arrow] e⁺e⁻[gamma] / [mu]⁺ [mu]⁻ [gamma] process and measure the helicity amplitudes that govern it. This study provides sensitivity to the interference terms between different quantum states and through the interference terms to the possible new physics. The final state is comprised of leptons (muon-antimuon or electron-positron pairs) with transverse momentum over 20 GeV and a photon with transverse energy over 30 GeV. Helicty amplitudes are measured for the total angular momentum of the quark-antiquark system up to J[subscript]q[subscript bar]q = 2. Four-dimensional multivariate analysis of the 2011 CMS data shows no significant deviations from the standard model prediction for the measured amplitudes.