A Search in the Two-Photon Final State for Evidence of New Particle Production in pp Collisions at $\sqrt{s}$ = 7 TeV

This thesis presents a search for evidence of new particle production in the twophoton + jets + missing transverse energy final state using the 2011 Large HadronCollider proton-proton data, at a center-of-mass energy of 7 TeV, collected by theCompact Muon Solenoid experiment. The distinctive signature of two photons, jets,and a momentum imbalance in the plane transverse to the proton beam direction ischiefly motivated by the theory of supersymmetry, which may provide a solution tothe hierarchy problem in particle physics. The instrumental background from ordinaryquantum chromodynamics and W → eν production dominates the total backgroundestimate, and is measured from the data. This background estimate, as well as thehigh efficiency (∼ 80%) to select and identify two high-energy photons in the data,relies on the superior energy resolution of the lead tungstate crystal electromagneticcalorimeter of the Compact Muon Solenoid. Signal efficiencies for gauge-mediatedsupersymmetric models, ranging from a few percent to approximately 25%, are takenfrom Monte Carlo simulation. No evidence of new particles is found in a datasetcorresponding to 4.7 fb−1 of integrated luminosity. Upper limits between 5 and 15fb on the cross sections of various new physics models are set at the 95% confidencelevel. The upper limits measured in this search are the most stringent to date forgauge-mediated models of supersymmetry.