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Register a new userHiggs Boson Searches and the Hbbar Coupling at the LHeC
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Once the existence of the Higgs boson is established at the CERN Large Hadron Collider (LHC), the focus will be shifted toward understanding its couplings to other particles. A crucial aspect is the measurement of the bottom Yukawa coupling, which is challenging at the LHC. In this paper we study the use of forward jet tagging as a means to secure the observation and to significantly improve the purity of the Higgs boson signal in the H to bbar decay mode from deep inelastic electron-proton scattering at the LHC. We demonstrate that the requirement of forward jet tagging in charged current events strongly enhances the signal-to-background ratio. The impact of a veto on additional partons is also discussed. Excellent response to hadronic shower and b-tagging capabilities are pivotal detector performance aspects.
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We present results from CDF and D0 on direct searches for high mass standard model (SM) Higgs boson (H) in ppbar collisions at the Fermilab Tevatron at sqrt(s) = 1.96 TeV. Compared to previous Higgs boson Tevatron combinations, more data and new channels (H -> W+W- -> lnujj, H -> WW -> l+tau + X and trilepton final states) have been added. Most previously used channels have been reanalyzed to gain sensitivity. Analyzing 5.9 fb^-1 of data at CDF, and 5.4-6.7 fb^-1 at D0, the combination excludes with 95% C.L. a standard model Higgs boson in the mass range of m_H = 158-175 GeV/c2.
The search for the Higgs boson, both in the context of the standard model and extensions to it, has been a key focus during Run II of the Tevatron. I report on the status of these searches, which are highlighted by evidence at the 3 standard deviation level for the SM Higgs in its $bbar{b}$ decay mode, the strongest direct evidence to date for fermionic couplings of the Higgs boson.
The prospects of observing the non-resonant di-Higgs production in the Standard Model at the proposed high energy upgrade of the LHC, $viz.$ the HE-LHC$~$($sqrt{s}=27~{rm TeV}$ and $mathcal{L} = 15~{rm ab^{-1}}$) is studied. Various di-Higgs final states are considered based on their cleanliness and signal yields. The search for the non-resonant double Higgs production at the HE-LHC is performed in the $bbar{b}gammagamma$, $bbar{b}tau^{+}tau^{-}$, $bbar{b}WW^{*}$, $WW^{*}gammagamma$, $bbar{b}ZZ^{*}$ and $bbar{b}mu^{+}mu^{-}$ channels. The signal-background discrimination is performed through multivariate analyses using the Boosted Decision Tree Decorrelated$~$(BDTD) algorithm in the$~$TMVA framework, the XGBoost toolkit and Deep Neural Network$~$(DNN). The variation in the kinematics of Higgs pair production as a function of the self-coupling of the Higgs boson, $lambda_{h}$, is also studied. The ramifications of varying $lambda_{h}$ on the $bbar{b}gammagamma$, $bbar{b}tau^{+}tau^{-}$ and $bbar{b}WW^{*}$ search analyses optimized for the SM hypothesis is also explored.
Vector-boson pair production is an important background for Higgs boson and new physics searches at the Large Hadron Collider LHC. We have calculated the loop-induced gluon-fusion process gg -> WW -> leptons, allowing for arbitrary invariant masses of the intermediate W bosons. This process contributes at O(alpha_s^2) relative to quark-antiquark annihilation, but its importance is enhanced by the large gluon flux at the LHC and by experimental cuts employed in Higgs boson searches. We find that gg -> WW provides only a moderate correction (ca. 5%) to the inclusive W-pair production cross section at the LHC. However, after taking into account realistic experimental cuts, the gluon-fusion process becomes significant and increases the theoretical WW background estimate for Higgs searches in the pp -> H -> WW -> leptons channel by approximately 30%.
A summary of the Higgs boson searches by the ATLAS and CMS collabrations using 1 f b-1 of LHC data is presented, concentrating on the Standard Model Higgs boson. Both experiments have the sensitivity to exclude at 95% CL a Standard Model Higgs boson in most of the Higgs boson mass region between about 130 GeV and 400 GeV. The observed data allow the exclusion of a Higgs Boson of mass 155 GeV to 190 GeV and 295 GeV to 450 GeV (ATLAS) and 149 GeV to 206 GeV and 300 GeV to 440 GeV (CMS). The lower limits are not as constraining as might be expected due to an excess in both experiments of order 2-3{sigma} which could be related to a low mass Higgs boson or to a statistical fluctuation.
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