Techniques For The Detection Of A New Physics Signature With The Cms Experiment

Abstract

This document investigates experimental and theoretical issues relating to the detection of physics beyond the Standard Model using the Compact Muon Solenoid (CMS). First, the structure of the CMS detector is reviewed. Particular attention is paid to the hardware and software components of the pixel tracking system. A description is presented of the algorithms that are used to reconstruct physics objects such as electrons and jets. Next, theoretical motivations are given for seeking new physics processes in the energy regime that is accessible by CMS. Two different theories, the Minimal Supersymmetric Standard Model and the Littlest Higgs model with T-parity, are introduced as extensions of the Standard Model. Their experimental signatures are considered, and a technique for discriminating between them using CMS observations is studied with Monte Carlo computer simulations. The remainder of the document focuses on a search for evidence of a new physics signature using CMS events that contain two electrons, two jets, and large missing transverse energy. A data-driven technique for estimating the QCD background due to fake electrons is developed, tested, and applied to this channel. The other background estimates are obtained from Monte Carlo simulations, and several sources of systematic uncertainty are surveyed. A correction factor to the Monte Carlo backgrounds is calculated from the electron recon- struction efficiencies in data and in simulation, which are measured using a tag and probe procedure. A statistical model is developed for propagating all of the background uncertainties to the calculation of the signal. Both Bayesian and semi-frequentist measures of significance are considered. The expected value of the signal is s = 0.238 ± 0.996 (stat) ± 0.304 (sys) events, and its 95% confidence interval is [0, 4.4].