Measurements Of Cross Section Of Gluon-Gluon Fusion Production Of Higgs Boson In Association With At Least 2 Jets Using H→WW~*→eνμν Decay Channel With The ATLAS Detector

In 2012,the Higgs boson was discovered by the ATLAS and CMS collaborations,which means the last elementary particle in the Standard Model was observed.Up to now,all the measurement results about Higgs properties at the Large Hadron Collider（LHC）are in good agreement with the Standard Model.With more data collected at the LHC,the precision of measurements will be further improved,which can provide stricter tests on the Standard Model predictions.At the same time,the distinctive properties of the Higgs boson also provide important clues to search for new physics.The gluon fusion（ggF）production of Higgs boson is the dominant production process in proton-proton collisions at the LHC.It takes up 87%,so the ggF production is the most important channel to study Higgs properties.The Higgs boson can get larger momentum when it is produced in association with jets,where the results are more sensitive to new physics.Thus the measurement of the Higgs boson properties in the ggF+≥2 jet final state provides chances to observe any possible deviations from the Standard Model prediction.Based on the full Run 2 dataset with an integrated luminosity of 139 fb-1 taken by the ATLAS detector at the center-of-mass energy（?）=13 TeV,In this thesis,the total and differential cross sections are measured for the process of ggF+≥2 jet,H+WW*→eνμν.The first analysis is to measure the cross section of Higgs boson production by the gluon fusion in association with two or more jets,and the result shows that the observed signal strength is μggF2J=1.22_-0.54^+0.60.A combined fit is further performed with the results of ggF N_jet=0 and=1 jet,ggF+≥2 jet,and VBF channels.The cross section times branching ratio of πggF·BH→WW*andσVBF·B_H→WW* are simultaneously measured to be 12.0 ± 1.4 pb and 0.75_-0.16^+0.19 pb,which are consistent with their theoretical predictions of 10.4 ± 0.6 pb and 0.81±0.02 pb,respectively.The second analysis is to measure the different ial cross section of ggF+≥2 jet,H→WW*→eνμν,which can be compared directly with the theory calculation to test the SM theory.There are 13 observables chosen and studied because they are sensitive to the Higgs boson production or decay properties.First step is to perform a 2-dimensional likelihood fit to extract the signal events and then get their distributions in these 13 observables,which are further unfolded by the iterative Bayesian unfolding technique to get the observed differential cross section for each observable.Extensive optimization studies are carried out in this thesis,including binning optimization and the regularization parameter optimization for the iterative Bayesian unfolding method.As only control regions are unblinded,a Hybrid dataset is used to perform the measurement for the expected differential cross-section distributions.