Abstract
A search for resonant and nonresonant pair production of Higgs bosons in the bb[over ¯]τ^{+}τ^{-} final state is presented. The search uses 36.1 fb^{-1} of pp collision data with sqrt[s]=13 TeV recorded by the ATLAS experiment at the LHC in 2015 and 2016. Decays of the τ-lepton pairs with at least one τ lepton decaying to final states with hadrons and a neutrino are considered. No significant excess above the expected background is observed in the data. The cross-section times branching ratio for nonresonant Higgs boson pair production is constrained to be less than 30.9fb, 12.7 times the standard model expectation, at 95%confidence level. The data are also analyzed to probe resonant Higgs boson pair production, constraining a model with an extended Higgs sector based on two doublets and a Randall-Sundrum bulk graviton model. Upper limits are placed on the resonant Higgs boson pair production cross-section times branching ratio, excluding resonances X in the mass range 305 GeV<m_{X}<402 GeV in the simplified hMSSM minimal supersymmetric model for tanβ=2 and excluding bulk Randall-Sundrum gravitons G_{KK} in the mass range 325 GeV<m_{G_{KK}}<885 GeV for k/M[over ¯]_{Pl}=1.
Highlights
Experiment at the LHC in 2015 and 2016
This Letter describes a search for resonant and nonresonant Higgs boson pair production in a final state with two b quarks and two τ leptons using 36.1 fb−1 of pp collision
The boosted decision tree (BDT) are more sensitive to the box diagram where the two Higgs bosons are produced at higher pT and the selection efficiency is greater
Summary
[23,24,25,26,27] using the CT10 parton distribution function (PDF) set [28]. Parton showers and hadronization were simulated with HERWIG++ [29] using the UEEE5 set of tuned parameters (tune) [30]. The BDTs are more sensitive to the box diagram where the two Higgs bosons are produced at higher pT and the selection efficiency is greater In both channels, simulated events are used to model background processes containing reconstructed τhad-vis that are matched to generated τhad within ΔR 1⁄4 0.2 (subsequently referred to as true τhad) and other minor background contributions. In order to account for potential acceptance differences between control and signal regions, the normalization of the tt background containing true τhad, determined predominantly from the τlepτhad SR in the final fit, is allowed to vary within a range determined by the acceptance variations associated with the tt modeling uncertainties This amounts to þ30%= − 32% for the τhadτhad SR and þ8.1%= − 9.3% for the Z → μμ þ heavy-flavor control region. Gkk at exp limit mG=500 GeV, k/MPl=1 Top-quark jet → τhad fakes Z → ττ +(bb,bc,cc) Other
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