Search for a Charged Higgs Boson Produced in the Vector-Boson Fusion Mode with Decay $H^{\pm }\to W^{\pm }Z$ using $pp$ Collisions at $\sqrt{s}=8\mathrm{TeV}$ with the ATLAS Experiment

A search for a charged Higgs boson, $H^{\pm }$, decaying to a $W^{\pm }$ boson and a $Z$ boson is presented. The search is based on $20.3{\mathrm{fb}}^{-1}$ of proton-proton collision data at a center-of-mass energy of 8 TeV recorded with the ATLAS detector at the LHC. The $H^{\pm }$ boson is assumed to be produced via vector-boson fusion and the decays $W^{\pm }\to q\overline{q^{\prime }}$ and $Z\to e^{+}{e}^{-}/{\mu }^{+}{\mu }^{-}$ are considered. The search is performed in a range of charged Higgs boson masses from 200 to 1000 GeV. No evidence for the production of an $H^{\pm }$ boson is observed. Upper limits of 31–1020 fb at 95% C.L. are placed on the cross section for vector-boson fusion production of an $H^{\pm }$ boson times its branching fraction to $W^{\pm }Z$. The limits are compared with predictions from the Georgi-Machacek Higgs triplet model.

Figure 1

The $m_{\ell \ell jj}$ distribution for data and the expected SM background. The hashed band indicates the postfit systematic uncertainty. Included in the plot is an example signal sample with $m_{H^{\pm }}=400\mathrm{GeV}$, which has been plotted with a cross section times branching fraction, $\sigma \times \mathrm{BR}(H^{\pm }\to W^{\pm }Z)=1\mathrm{pb}$ for illustration. No data events are observed for values of $m_{\ell \ell jj}>600\mathrm{GeV}$.

Figure 2

Exclusion limits in fb at the 95% C.L. for the vector-boson fusion production cross section of a $H^{\pm }$ boson times its branching fraction to $W^{\pm }Z$, assuming the signal has a narrow intrinsic width. Also included on the plot are the median, $\pm 1\sigma$, and $\pm 2\sigma$ values within which the limit is expected to lie in the absence of a signal.

Figure 3

Exclusion limits at the 95% C.L. for $s_H$ versus $m_{H^{\pm }}$ in the Georgi-Machacek Higgs triplet model. Also included on the plot are the median, $\pm 1\sigma$, and $\pm 2\sigma$ values within which the limit is expected to lie in the absence of a signal.