The main motivation of the Compact Muon Solenoid (CMS) experiment is to explore and to discover physics underlying electro-weak asymmetry breaking. Beside this, CMS detector provides an opportunity to do various experiments for detecting new physics signatures beyond the Standard Model (SM). Investigation of these signatures requires the identification and precise energy and moment measurement of electrons, muons, photons, and jets. The objective of this thesis is the calculation of the efficiencies for the measurement of W charge asymmetry in inclusive pp→W (μυ) production. The charge asymmetry is defined to be the difference between W^+ and W^- bosons, normalized to the sum. This asymmetry is sensitive to the u-quark and d-quark ratios in the proton and precise measurement of the W charge asymmetry can provides new insights to the proton structure functions. Therefore, to improve understanding of SM backgrounds in search for new physics, the moun trigger, isolation, reconstruction, identification efficiencies has been studied using partial data collected by the CMS detector during pp collisions at the LHC in 2011. The dataset corresponds to an integrated luminosity of 2.31 fb-1. The efficiencies are measured as functions of the decay muon pseudo rapidity and transverse momentum based on "tag and probe" method. The efficiency measurements are compared to their estimated value from the Monte Carlo simulations so as to provide scaling factors to correct to the residual mis-modeling of the CMS muon performance. The comparison with simulations based on MC simulations opens a gate for validation of the detector simulation and optimization of selection strategies.

This dissertation presents muon charge asymmetry, fiducial differential cross section and CMS single muon trigger efficiency measurements as a function of muon pseudorapidity for inclusive W→μν events produced in proton-proton collisions at the LHC. The data were recorded by the CMS detector at a center-of-mass energy of 8 TeV and correspond to an integrated luminosity of 18.8 fb-1. Several comparisons are performed to cross-check the experimental results. Muon efficiency measurements are compared to estimated values from Monte Carlo simulations and reference values recommended by CMS physics object groups. The differential cross section and the charge asymmetry measurements are compared to theoretical predictions based on next-to-leading order and next-to-next-to-leading order QCD calculations with different PDF models. Inputs from the charge asymmetry and the differential cross section measurements for the determination of the next generation of PDF sets are expected to bring different predictions closer together and aid in reducing PDF uncertainties. The impact of the charge asymmetry on PDFs has been investigated by putting the asymmetry results into a QCD analysis at next-to-leading order and next-to-next-leading order with inclusive deep-inelastic scattering data from HERA. Significant improvement of the accuracy on the valence-quark distributions is observed. This measurement is recommended for more accurate constraints in future PDF determinations. More precise measurements of PDFs will improve LHC predictions.

The Standard Model of particle physics is a successful theory, yet it is incomplete. Supersymmetry is one of the favoured extensions of the Standard Model, elegantly addressing several unresolved issues. This thesis presents a search for the pair production of supersymmetric particles chargino one and neutralino two, where the neutralino two decays to the lightest neutralino and the 125 GeV Higgs boson. The final states considered for the search have large missing transverse momentum, an isolated lepton and two jets identified as originating from bottom quarks. The analysis is based on 20.3 inverse femtobarns of 8 TeV proton-proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. No excess over Standard Model predictions is observed. The analysis has been combined with three independent searches that probe other decay modes of the Standard Model Higgs boson. Limits are set at 95% confidence level in the context of a simplified supersymmetric model. Common masses of chargino one and neutralino two are excluded up to 250 GeV for a massless neutralino one. The analysis of this dissertation has been reinterpreted in the context of a large scan of the phenomenological Minimal Supersymmetric Standard Model, along with 22 other ATLAS Run 1 searches. The resulting summary paper represents the most comprehensive assessment of the ATLAS constraints on Supersymmetry models to date. / Graduate / 0798 / cdavid@uvic.ca