A search for doubly charged Higgs bosons with pairs of prompt, isolated, highly energetic leptons with the same electric charge is presented. The search uses a proton-proton collision data sample at a centre-of-mass energy of 13 TeV corresponding to 36.1 $\mathrm{ fb}^{ -1}$ of integrated luminosity recorded in 2015 and 2016 by the ATLAS detector at the LHC. This analysis focuses on the decays $H^{ \pm\pm}\rightarrow e^{ \pm}e^{ \pm}$, $H^{ \pm\pm}\rightarrow e^{ \pm}\mu^{ \pm}$ and $H^{ \pm\pm}\rightarrow \mu^{ \pm}\mu^{ \pm}$, fitting the dilepton mass spectra in several exclusive signal regions. No significant evidence of a signal is observed and corresponding limits on the production cross-section are derived at 95% confidence level. The observed lower limit on the mass of a doubly charged Higgs boson only coupling to left-handed leptons ($e$,$\mu$) varies from 770 GeV to 870 GeV (850 GeV expected) for $B(H^{ \pm\pm}\rightarrow \ell^{ \pm}\ell^{ \pm})$ = 100% and both the expected and observed mass limits are above 450 GeV for $B(H^{ \pm\pm}\rightarrow \ell^{ \pm}\ell^{ \pm})$ = 10% and any combination of partial branching ratios.
Categories: hep-ex