A search for the Higgs boson in H->WW->lvlv with 8.2 fb-1

Higgs;Collider Detector at Fermilab (CDF);Tevatron

Carls, Benjamin

关键词: Higgs;    Collider Detector at Fermilab (CDF);    Tevatron;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/31020/Carls_Benjamin.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

This thesis documents a search for Standard Model (SM) Higgs boson to WW production in the final stateof two charged leptons (e, μ) and two neutrino final state resulting from in pp collisions at√s = 1.96 TeV.The data collected by the CDF II detector at the Tevatron collider at Fermilab, corresponds to an integratedluminosity of 8.2 fb−1.This iteration of the analysis incorporated several improvements to increase Higgs sensitivity. We reevaluatedlepton isolation values to recover signal events in which leptons mutually spoil each other’s isolationrequirements. We additionally incorporated new lepton identification selections, namely likelihood basedforward electrons and a better recovery of electrons passing through detector cracks.The base analysis searches for opposite-sign dilepton events. We employed three separately trained neuralnetworks to distinguish signal from background processes for events with 0, one, or two jets. To furtherincrease sensitivity for 0-jet events, we constructed a likelihood ratio discriminant based on Matrix Elementcalculations as an additional input to the neural network. For the base opposite-sign analysis, summing overall jet multiplicities, we observed 3513 events in data compared with a background expectation of 3409 ± 233and a signal expectation of 53.6 ± 9.4 for a mass of 165 GeV/c2.To further increase signal acceptance, we incorporated several separate search regions in addition to thebase analysis. We include subchannels searching for Higgs production in events with low dilepton invariantmass and in events having final states with either same-sign dileptons or trileptonsWith the combination of the separate analyses, we observed a 95% C.L. upper production limit of 0.77times the SM expectation for a Higgs mass of 165 GeV/c2 to be compared with the value for the median of theexpected limit (0.78). We additionally present results for eighteen Higgs masses ranging from 110 GeV/c2to 200 GeV/c2. We excluded at the 95% C.L., a SM Higgs boson in the mass range between 156 and175 GeV/c2.