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

• Received 14 July 2016

DOI:https://doi.org/10.1103/PhysRevD.94.032011

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© 2016 CERN, for the ATLAS Collaboration