Evidence of Higgs Boson Production through Vector Boson Fusion
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2015
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Abstract
The discovery of the Higgs boson in 2012 provided confirmation of the
proposed mechanism for preserving the electroweak $SU(2) \times U(1)$
gauge symmetry of the Standard Model of particle physics. It also
heralded in a new era of precision Higgs physics. This thesis presents a
measurement of the rate at which the Higgs boson is produced by vector
boson fusion in the $WW^{(\ast)}\rightarrow\,\ell\nu\ell\nu$ decay channel. With gauge boson couplings
in both the production and decay vertices, a VBF measurement in this
channel is a powerful probe of the $VVH$ vertex strength. Using
$4.5$~fb$^{-1}$ and $20.3$~fb$^{-1}$ of $pp$ collision data collected
at respective center-of-mass energies of 7 and $8 \tev$ in the ATLAS
detector, measurements of the statistical significance and the signal
strength are carried out in the Higgs mass range $100 \leq m_H \leq
200 \gev$. These measurements are enhanced with a boosted decision
tree that exploits the correlations between eight kinematic inputs in
order to separate signal and background processes. At the benchmark
Higgs mass of $125.36 \gev$, the significance of the data assuming the
background-only hypothesis to be true has been observed to be
$3.2\sigma$ ($2.7\sigma$ expected), constituting evidence of VBF Higgs boson
production. The measured signal strength (ratio of observed cross section times
branching ratio to that predicted by the SM) is
$1.27^{+0.53}_{-0.45}$. The inclusive cross section times
branching ratio is found to be $0.51^{+0.22}_{-0.17}$~pb at $\sqrts =
8 \tev$, consistent with the SM prediction of $0.34$~pb. No
significant deviations from the SM predictions for VBF Higgs boson
production are observed.
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Cerio, Benjamin C (2015). Evidence of Higgs Boson Production through Vector Boson Fusion. Dissertation, Duke University. Retrieved from https://hdl.handle.net/10161/9820.
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