Search for the Higgs boson and rare standard model processes in the ET+B-jets signature at the Collider Detector at Fermilab
Abstract
We study rare processes of the standard model of particle physics (SM) in events with missing transverse energy ([special characters omitted]), no leptons, and two or three jets, of which at least one is identified as originating from a b-quark ([special characters omitted]+b-jets signature). We present a search for the SM Higgs boson produced in association with a W or Z boson when the Higgs decays into bb¯. We consider the scenario where Z → νν, or W → lν and the lepton escapes detection. This dissertation analyzes 7.8 fb–1 of data collected by the CDF II experiment at Fermilab. For the first time, we analyze events with relaxed kinematic requirements, yielding an increase of 30-40% in acceptance to the WH/ZH signal. We collect events from three different triggers and parametrize the efficiency of their logical combination (OR) using a novel artificial neural network (NN) technique. To increase the sensitivity to the signal, we implement a NN to remove the huge instrumental background. An additional NN is used to discriminate the Higgs signal from the remaining background. We check our background modeling by comparing data against backgrounds in many control regions, and find good agreement. Observing no significant excess in the data, we place 95% confidence level (C.L.) upper limits on the Higgs boson production cross section. For a mass of 115 GeV/c 2 the expected (observed) limit is 2.9 (2.3) times the standard model prediction. Compared to the last iteration of this analysis, this result improves the significance by 10% throughout the 100–150 GeV/c 2 mass range. This is one of the most sensitive at the Tevatron in this mass range. We cross-check the tools developed in this dissertation by measuring the cross-section of top pair, electroweak single top and diboson ( WZ + ZZ) production.
Degree
Ph.D.
Advisors
Bortoletto, Purdue University.
Subject Area
Particle physics
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