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Overview of the \(H\rightarrow \textit{WW}\) Analysis

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Discovery and Measurement of the Higgs Boson in the WW Decay Channel

Part of the book series: Springer Theses ((Springer Theses))

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Abstract

The \(WW\) decay of the Higgs boson is a promising search channel as it has a large branching ratio (BR) for a wide range of \(m_H\). In fact, it is the most probable decay for \(m_H > 135\) GeV (see Fig. 1.5). This chapter will describe the experimental search for \(gg\rightarrow H \rightarrow WW \rightarrow \ell \nu \ell \nu \) (where \(\ell = { e}, \mu \)) using the 2012 dataset of \(pp\) collisions at \(\sqrt{s} = 8\)  TeV. The search strategy is optimised for a low mass Higgs boson, as favoured by electroweak fits, and thus accounts for off-shell \(W\) bosons.

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Notes

  1. 1.

    Events with one or two \(W \rightarrow \tau \nu \) decays can contribute to the dileptonic search when the \(\tau \) decays to an electron or muon. This contribution is small however, since \(\text {BR}({\tau \rightarrow \ell \nu _{\ell }\nu _{\tau }}) = 17.6\,\%\) [1]. Also, the kinematics of such events are different due to the additional decay(s) and neutrinos.

  2. 2.

    Each SCT module comprises two layers of silicon strips with a small stereo angle, enabling the three-dimensional coordinate to be precisely measured (see Sect. 3.3.1).

  3. 3.

    A variety of muon reconstruction strategies are available: stand-alone muons have only MS tracks, combined muons have both MS and ID tracks, segment-tagged muons have ID tracks that match to an MS track segment, and calorimeter-tagged muons have ID tracks matched to the calorimeter deposit of a minimum ionising particle (used to recover efficiency at \(\eta \approx 0\), where detector services reduce the MS coverage). This thesis uses combined muons, which offer the best performance.

  4. 4.

    Significant hadronic shower energy is lost through slow neutrons, nuclear excitations and neutrinos.

  5. 5.

    ATLAS good runs list:

    figure b
    figure c

    .

  6. 6.

    A prescaled trigger reduces the threshold \(p_{\mathrm{T}}\) by recording only 1 in N events passing the trigger, and weighting such events by a factor N. In doing so, statistical power is lost.

  7. 7.

    It follows that events featuring an electron with \(p_{\mathrm{T}} < 15\) GeV must fire a single-lepton trigger, and thus the leading lepton must have \(p_{\mathrm{T}} > 25\) GeV.

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  1. Denys Wilkinson Building, University of Oxford, Oxford, UK

    David Hall

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  1. David Hall
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Correspondence to David Hall .

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Hall, D. (2015). Overview of the \(H\rightarrow \textit{WW}\) Analysis. In: Discovery and Measurement of the Higgs Boson in the WW Decay Channel. Springer Theses. Springer, Cham. https://doi.org/10.1007/978-3-319-19989-4_4

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