Jiggins, SP; (2018) Search for new resonances decaying to a Standard Model Vector boson (W/Z) and Higgs boson in the llbƃ, lνbƃ & vvbƃ channels, in proton-proton collisons at √s = 13 TeV with the ATLAS detector. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The following thesis presents the result of a Beyond the Standard Model search for heavy resonances (V'/A) decaying into a Standard Model W or Z boson, and a Higgs (h) boson with a final state signature llbb̄, lνbb̄, or ννbb̄, where l= e/μ , in proton-proton collisions at a center of mass energy of √s = 13 TeV. The data is collected using the ATLAS detector at the Large Hadron Collider, during the data periods of 2015+2016, amounting to 36.1 fb^{-1}. The search is conducted using the (transverse) invariant mass spectrum of the reconstructed Standard Model W/Z boson and Higgs boson system, W/Z + h, to search for excesses using the CL_{s} binned profile likelihood test statistic. No excess is observed, therefore the results are interpreted in terms of constraints on σ_{V/A} × BR(h→bb̄), for heavy vector bosons predicted by Heavy Vector Triplet models (HVT ), W'/Z', or the CP-odd scalar boson A predicted by Two-Higgs Doublet Models (2HDM ). The upper limits on the production cross-sections are then used to assign constraints to the model parameter space. For the HVT interpretation, limits on two benchmark models corresponding to fermiophobic and fermiophilic extensions, labelled A and B, of the heavy resonances are set: m_{V'} = 2800(2930) GeV. For 2HDMs, limits on the production cross-section for mediator masses ranging from 220-2000 GeV are set: 5.5 × 10^{−3} pb → 2.4 × 10^{−1} pb for gg→A production, and 3.4 × 10^{−3} → 7.3 × 10^{−1} pb for bbA associated production.

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