Measurement of exclusive $\gamma \gamma \to W^{+}{W}^{-}$ production and search for exclusive Higgs boson production in $pp$ collisions at $\sqrt{s}=8$ TeV using the ATLAS detector

Searches for exclusively produced $W$ boson pairs in the process $pp(\gamma \gamma )\to p{W}^{+}{W}^{-}p$ and exclusively produced Higgs boson in the process $pp(gg)\to pHp$ have been performed using $e^{\pm }{\mu }^{\mp }$ final states. These measurements use 20.2 fb${}^{-1}$ of $pp$ collisions collected by the ATLAS experiment at a center-of-mass energy $\sqrt{s}=8$ TeV at the LHC. Exclusive production of $W^{+}{W}^{-}$ consistent with the Standard Model prediction is found with 3.0$\sigma$ significance. The exclusive $W^{+}{W}^{-}$ production cross-section is determined to be $\sigma (\gamma\gamma\rightarrow W^{+}W^{-}\rightarrow e^{\pm}\mu^{\mp} X) = 6.9 \pm 2.2 ($\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}\mathrm{.}$) \pm 1.4 ($\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{.}$)$ fb, in agreement with the Standard Model prediction. Limits on anomalous quartic gauge couplings are set at 95% confidence-level as $-1.7 \times 10^{-6} < a_0^W/\Lambda^2 < 1.7 \times 10^{-6}$GeV$^{-2}$and$-6.4 \times 10^{-6} < a_C^W/\Lambda^2 < 6.3 \times 10^{-6}$GeV$^{-2}$. A 95% confidence-level upper limit on the total production cross-section for exclusive Higgs boson is set to 1.2 pb.