Abstract
Many extensions of the Standard Model (SM) contain (pseudo)scalar bosons with masses in the TeV range. At hadron colliders, such particles would predominantly be produced in gluon fusion and would decay into top quark pair final sates, a signal that interferes with the large QCD background ggto toverline{t} . This phenomenon is of interest for searches for by the LHC experiments. Here, we consider the signal and background interference in this process and study it in various benchmark scenarios, including models with extra singlet (pseudo)scalar resonances, two-Higgs doublet models (2HDM), and the minimal supersymmetric extension of the SM with parameters chosen to obtain the measured light Higgs mass (the hMSSM). We allow for the possible exchanges of beyond the SM vector-like particles as well as scalar quarks. We calculate the possible interference effects including realistic estimates of the attainable detection efficiency and mass resolution. Studies of our benchmark scenarios indicate that searches with an LHC detector could permit the observation of the toverline{t} final states or constrain significantly large regions of the parameter spaces of the benchmark scenarios.
Highlights
Of a 750-GeV feature in the γγ spectrum at the LHC [27, 31], but their principles have broader applicability
As we show in this paper using various benchmark scenarios, including a model with an extra scalar singlet and models with two Higgs doublets such as the 2HDM and the MSSM, interference signatures in the cross section for producing ttfinal states at the LHC provide distinctive and sensitive signatures for searches of new physics beyond the Standard Model (SM)
We have explored in this paper the prospective sensitivity of LHC measurements of the ttinvariant-mass spectrum to various beyond the Standard Model (BSM) scenarios with additional heavyscalar bosons, via the peak-and-dip features induced by interference between BSM and SM contributions to the production amplitude that are illustrated at the parton level in figure 3
Summary
We consider first a minimal benchmark model, namely the SM supplemented by just one of the following terms for the interaction of a heavy scalar H or pseudoscalar A with the top quark: LnewYukawa ⊃ −gHttttH or igAtttγ5tA. We use the SM-like Higgs coupling to fermions as a reference, expressing these new scalar and pseudoscalar couplings to the top quark in the form: gΦtt mt v. √ where Φ = H or A, and with the vev v = 1/ 2GF = 246 GeV With this definition, the SM Higgs coupling ghtt = mt/v corresponds to ghtt = 1. The Feynman rules associated with these couplings are obtained by multiplying gΦttby (−i). These new interactions induce ggΦ couplings via quantum corrections
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