Search for doubly charged Higgs boson production in multi-lepton final states with the ATLAS detector using proton-proton collisions at root s=13TeV

Abstract

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

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of integrated luminosity recorded in 2015 and 2016 by the ATLAS detector at the LHC. This analysis focuses on the decays

H

± ±

→

e ±

e ±

,

H

± ±

→

e ±

μ ±

and

H

± ±

→

μ ±

μ ±

, 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 and consequently a lower limit on

m (

H

± ±

)

are derived at 95% confidence level. With

ℓ ±

ℓ ±

=

e ±

e ±

/

μ ±

μ ±

/

e ±

μ ±

, the observed lower limit on the mass of a doubly charged Higgs boson only coupling to left-handed leptons varies from 770 to 870 GeV (850 GeV expected) for

B (

H

± ±

→

ℓ ±

ℓ ±

) = 100 %

and both the expected and observed mass limits are above 450 GeV for

B (

H

± ±

→

ℓ ±

ℓ ±

) = 10 %

and any combination of partial branching ratios.