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Register a new userHiggs boson production in association with top quarks in the POWHEG BOX
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Authors
Heribertus B. Hartanto
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We present results from the analytic calculation of top+antitop+Higgs hadronic production at Next-to-Leading Order in QCD interfaced with parton-shower Monte Carlo event generators in the POWHEG BOX framework. We consider kinematic distributions of the top quark and Higgs boson at the 8 TeV Large Hadron Collider and study the theoretical uncertainties due to specific choices of renormalization/factorization scales and parton-showering algorithms, namely PYTHIA and HERWIG. The importance of spin-correlations in the production and decay stages of a top/antitop quark is discussed on the example of kinematic distributions of leptons originating from the top/antitop decays. The corresponding code is now part of the public release of the POWHEG BOX.
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The hadronic production of a Higgs boson (H) in association with b jets will play an important role in investigating the Higgs-boson couplings to Standard Model particles during Run II of the CERN Large Hadron Collider, and could in particular reveal the presence of anomalies in the assumed hierarchy of Yukawa couplings to the third-generation quarks. A very high degree of accuracy in the theoretical description of this process is crucial to implement the rich physics program that could lead to either direct or indirect evidence of new physics from Higgs-boson measurements. Aiming for accuracy in the theoretical modeling of H+b-jet production, we have interfaced the analytic Next-to-Leading-Order QCD calculation of H-bottom-antibottom production with parton-shower Monte Carlo event generators in the POWHEG BOX framework. In this paper we describe the most relevant aspects of the implementation and present results for the production of H+1 b jet, H+2 b jets, and $H$ with no tagged b jets, in the form of kinematic distributions of the Higgs boson, of the b jets, and of the non-b jets, at the 13 TeV Large Hadron Collider. The corresponding code is part of the public release of the POWHEG BOX.
We analyse the production of a Higgs boson in association with a top--antitop-quark pair in the Standard Model at the LHC. Considering the final state consisting of four b jets, two jets, one identified charged lepton and missing energy, we examine the irreducible background for the production rate and several kinematical distributions. While ttH production and decay is roughly a fourth of the full process for the final state specified above, ttbb production constitutes the main contribution with about $92%$. Surprisingly, interference effects result in a reduction of the cross-section by five per cent. Furthermore, we consider NLO QCD corrections for the production of a Higgs boson, two charged leptons, two neutrinos, and two b jets. We discuss the size of the corrections and the scale dependence for the integrated cross section and different distributions. For the integrated cross section we find a $K$ factor of 1.17 and a reduction of the scale dependence from $30%$ at leading order to $5%$ at next-to-leading order.
The Madala hypothesis is the prediction of a new heavy scalar, the Madala boson, that has had previous success in explaining several anomalies in LHC Run 1 and 2 data. In the literature, the Madala boson has so far primarily been discussed in the context of its dominant production mode, gluon fusion. However, it can be shown that a study of its production in association with top quarks can provide us with crucial information about the model, as well as explain the enhancement of top associates Higgs production that has been observed in the data -- most notably in leptonic channels. For this study, Monte Carlo events have been produced and passed through a detector simulation. These events are then run through an event selection designed by a CMS search for a single top quark in association with a Higgs boson. A fit is made to the CMS data, yielding a parameter constraint on the Madala hypothesis. With the Madala hypothesis prediction, an effective signal strength is calculated and compared with the observed values.
We study the production of a Higgs boson in association with bottom quarks in hadronic collisions, and present phenomenological predictions relevant to the 13 TeV LHC. Our results are accurate to the next-to-leading order in QCD, and matched to parton showers through the MC@NLO method; thus, they are fully differential and based on unweighted events, which we shower by using both Herwig++ and Pythia8. We perform the computation in both the four-flavour and the five-flavour schemes, whose results we compare extensively at the level of exclusive observables. In the case of the Higgs transverse momentum, we also consider the analytically-resummed cross section up to the NNLO+NNLL accuracy. In addition, we analyse at ${cal O}(alpha_S^3)$ the effects of the interference between the $bbar{b}H$ and gluon-fusion production modes.
We discuss the calculation of charged Higgs boson production in association with top quark in the MC@NLO framework for combining NLO matrix elements with a parton shower. The process is defined in a model independent manner for wide applicability, and can be used if the charged Higgs boson mass is either greater or less than the mass of the top quark. For the latter mass region, care is needed in defining the charged Higgs production mode due to interference with top pair production. We give a suitable definition applicable in an NLO (plus parton shower) context, and present example results for the LHC.
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