Abstract
A search for heavy pseudoscalar (A) and scalar (H) Higgs bosons decaying into a top quark pair (tt[over ¯]) has been performed with 20.3 fb^{-1} of proton-proton collision data collected by the ATLAS experiment at the Large Hadron Collider at a center-of-mass energy sqrt[s]=8 TeV. Interference effects between the signal process and standard model tt[over ¯] production, which are expected to distort the signal shape from a single peak to a peak-dip structure, are taken into account. No significant deviation from the standard model prediction is observed in the tt[over ¯] invariant mass spectrum in final states with an electron or muon, large missing transverse momentum, and at least four jets. The results are interpreted within the context of a type-II two-Higgs-doublet model. Exclusion limits on the signal strength are derived as a function of the mass m_{A/H} and the ratio of the vacuum expectation values of the two Higgs fields, tanβ, for m_{A/H}>500 GeV.
Highlights
A search for heavy pseudoscalar (A) and scalar (H) Higgs bosons decaying into a top quark pair has been performed with 20.3 fb−1 of proton-proton collipsioffiffin data collected by the ATLAS experiment at the Large Hadron Collider at a center-of-mass energy s 1⁄4 8 TeV
No significant deviation from the standard model prediction is observed in the tt invariant mass spectrum in final states with an electron or muon, large missing transverse momentum, and at least four jets
Introduction.—The production of new particles at the Large Hadron Collider (LHC) with masses close to the TeV scale is predicted by many models of physics beyond the standard model (SM)
Summary
A search for heavy pseudoscalar (A) and scalar (H) Higgs bosons decaying into a top quark pair (tt) has been performed with 20.3 fb−1 of proton-proton collipsioffiffin data collected by the ATLAS experiment at the Large Hadron Collider at a center-of-mass energy s 1⁄4 8 TeV. The S and S þ I samples with this setup were generated separately for pseudoscalar and scalar Higgs bosons Event samples for both the S and S þ I components for different values of ðmA=H; tan βÞ were obtained from signal samples S after the detector simulation by applying an event-by-event reweighting. Signal hypotheses with mA=H < 500 GeV were not considered as they require an accurate modeling of the Higgs boson decay into virtual top quarks and the implementation of higher-order corrections that are not available in the MADGRAPH5_aMC@NLO model. Events with a resolved topology, in which the three jets from the hadronically decaying top quark are well separated in the detector, are selected This is the most efficient selection strategy for signal hypotheses with mA=H < 800 GeV.
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