In this paper, a search for Higgs boson production in association with a pair of top quarks ($ t\overline{t} $H) is performed, where the Higgs boson decays to $ b\overline{b} $ , and both top quarks decay hadronically. The data used correspond to an integrated luminosity of 20.3 fb -1 of pp collisions at √s = 8 TeV collected with the ATLAS detector at the Large Hadron Collider. The search selects events with at least six energetic jets and uses a boosted decision tree algorithm to discriminate between signal and Standard Model background. The dominant multijet background is estimated using a dedicated data-driven technique. For a Higgs boson mass of 125 GeV, an upper limit of 6.4 (5.4) times the Standard Model cross section is observed (expected) at 95% confidence level. The best-fit value for the signal strength is [mu] = 1.6 ± 2.6 times the Standard Model expectation for mH = 125 GeV. Combining all $ t\overline{t}$H searches carried out by ATLAS at √s = 8 and 7 TeV, an observed (expected) upper limit of 3.1 (1.4) times the Standard Model expectation is obtained at 95% confidence level, with a signal strength [mu] = 1.7 ± 0.8.

This thesis presents a search for Standard Model Higgs boson produced in association with top quark pairs, ttH. The analysis uses 13.2 fb-1 of pp collision data at √s = 13 TeV collected in 2015 and 2016 with the ATLAS detector at the LHC. The considered decay mode for the Higgs boson is H->bb and the single lepton decay channel (electron or muon) for the tt pair. The sensitivity of this channel is improved by an event categorisation according to the jet multiplicity and the number of jets containing a b-hadron decay. Multivariate techniques are used to distinguish the signa...

A search for the standard model Higgs boson is shown in the associated production channel with a Z boson and decay to bottom quarks. The data for this search was gathered from April 2011 until December 2012. The dataset corresponds to 5.0 fb ... 1 of pp collisions at p s = 7 TeV and 19.04 fb ... 1 of pp collisions at p s = 8 TeV . An excess of events is observed above the expected background with a local significance of 2.1 standard deviations, which is consistent with the expectation from the production of the standard model Higgs boson.

A search for the standard model Higgs boson is presented in the associated production channel Z ([Pi]) H (bb ) where each tau decays leptonically, one to an electron, the other to a muon and associated neutrinos. A data sample comprising of 5.0 fb[superscript -1] and 19.0 fb[superscript -1] from the 2011 and 2012 proton collision running periods at a center of mass of 7 and 8TeV, respectively, has been analyzed and 95% C.L. upper limits derived for Higgs masses of 110-135 GeV. vi

A search for the standard model Higgs boson (H) decaying to b b-bar when produced in association with a weak vector boson (V) is reported for the following channels: W(mu nu)H, W(e nu)H, W(tau nu)H, Z(mu mu)H, Z(e e)H, and Z(nu nu)H. The search is performed in data samples corresponding to integrated luminosities of up to 5.1 inverse femtobarns at sqrt(s) = 7 TeV and up to 18.9 inverse femtobarns at sqrt(s) = 8 TeV, recorded by the CMS experiment at the LHC. An excess of events is observed above the expected background with a local significance of 2.1 standard deviations for a Higgs boson mass of 125 GeV, consistent with the expectation from the production of the standard model Higgs boson. The signal strength corresponding to this excess, relative to that of the standard model Higgs boson, is 1.0 +/- 0.5./abstract