This thesis describes the first search for Standard Model Higgs boson production in association with a top-antitop quark pair in proton-antiproton collisions at a centre of mass energy of 1.96 TeV. The integrated luminosity for othis search corresponds to 319 pb-1 of data recorded by the Collider Detector at Fermilab. We outline the even selection criteria, evaluate the even acceptance and estimate backgrounds from Standard Model sources. These events are observed that satisfy our event selection, while 2.16 ± 0.66 events are expected from background processes. no significant excess of events above background is thus observed, and we set 95% confidence level upper limits on the production cross section for this process as a function of the Higgs mass. For a Higgs boson mass of 115 GeV/c2 we find that [sigma]$t\bar{t}H$ x BR (H 2!bb)

This thesis describes the first search for Standard Model Higgs boson production in association with a top-antitop quark pair in proton-antiproton collisions at a centre of mass energy of 1.96 TeV. The integrated luminosity for this search corresponds to 319 pb-1 of data recorded by the Collider Detector at Fermilab. We outline the event selection criteria, evaluate the event acceptance and estimate backgrounds from Standard Model sources. Three events are observed that satisfy our event selection, while 2.16 +/- 0.66 events are expected from background processes. No significant excess of events above background is thus observed, and we set 95% confidence level upper limits on the production cross section for this process as a function of the Higgs mass. For a Higgs boson mass of 115 GeV/ c2, we find that sigmatt H x BR(H b b)

We present a search for a standard model Higgs boson produced in association with a W boson using data collected with the CDF II detector from proton/antiproton collisions at a center of mass energy of 1.96 TeV. The search is performed in the WH channel where the W boson decays leptonically and the Higgs boson decays to a bottom/antibottom quark pair. The two quarks usually fragment into two jets, but sometimes a third jet can be produced via gluon radiation, so we have increased the standard two-jet sample by including events that contain three jets. We reconstruct the Higgs boson using two or three jets depending on the kinematics of the event. We find an improvement in our search sensitivity using the larger sample together with this multijet reconstruction technique. Our data show no evidence of a Higgs boson, so we set 95% confidence level upper limits on the WH production rate. We set limits between 3.36 and 28.7 times the standard model prediction for Higgs boson masses ranging from 100 to 150 GeV/c^2.

We present a search for the standard model Higgs boson produced with a Z boson in 4.1 fb−1 of data collected with the CDF II detector at the Tevatron. In events consistent with the decay of the Higgs boson to a bottom-quark pair and the Z boson to electrons or muons, we set 95% credibility level upper limits on the ZH production cross section times the H --> b{bar b} branching ratio. Improved analysis methods enhance signal sensitivity by 20% relative to previous searches beyond the gain due to the larger data sample. At a Higgs boson mass of 115 GeV/c2 we set a limit of 5.9 times the standard model value.

Results for the search of a Higgs boson decaying to a bottom quark-antiquark pair produced with a top quark-antiquark pair (t ̄tH) in the lepton plus jets channel in proton-proton collisions at a center-of-mass energy of √ s = 13 TeV are presented. The data used corresponds to an integrated luminosity of 12.9 fb−1 recorded with the CMS experiment in 2016. To increase the sensitivity of the search, selected events are categorized by number of jets and number of b-tagged jets resulting in different expected signal and background rates. For each category two multivariate techniques are combined to separate the signal and background events. A machine learning process called a boosted decision tree (BDT) is trained on the two types of classes of events and then split into high and low purity based on the output. The physics motivated matrix element method (MEM) is applied to the BDT output to obtain the final two dimensional discriminator. The result is presented in terms of the t ̄tH signal strength modifier μ, the ratio of the observed t ̄tH production cross section relative to the expected cross section based on a 125 GeV Standard Model Higgs boson. A combined fit of the final discriminant in all categories of the lepton plus jets channel results an observed (expected) upper limit of μ