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 text {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 and consequently a lower limit on m(H^{pm pm }) are derived at 95% confidence level. With ell ^{pm }ell ^{pm }=e^{pm }e^{pm }/mu ^{pm }mu ^{pm }/e^{pm }mu ^{pm }, 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^{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.
Highlights
Events with two prompt, isolated, highly energetic leptons with the same electric charge are produced very rarely in a proton–proton collision according to the predictions of the standard model (SM), but may occur with higher rate in various theories beyond the standard model (BSM)
Charged Higgs bosons can arise in a large variety of BSM theories, namely in left-right symmetric (LRS)
The ATLAS detector at the Large Hadron Collider was used to search for doubly charged Higgs bosons in the same-charge dilepton invariant mass spectrum at high values, using e±e±, e±μ± and μ±μ± final states as well as final states with three or four leptons
Summary
Events with two prompt, isolated, highly energetic leptons with the same electric charge (same-charge leptons) are produced very rarely in a proton–proton collision according to the predictions of the standard model (SM), but may occur with higher rate in various theories beyond the standard model (BSM). Theoretical studies [19,20,21] indicate that the doubly charged Higgs bosons would be predominantly pair-produced via the Drell–Yan process at the LHC For this search, the cross-sections utilised to set the final exclusion limits are computed according to the model in Ref. Higgs triplet vacuum expectation value v , it decays almost exclusively to leptons while for high values of v the decay is mostly to a pair of W bosons [9,12] In this analysis, the coupling to W bosons is assumed to be negligible and only pair production via the Drell–Yan process is considered. A software-based high-level trigger executes algorithms similar to those used in the offline reconstruction software, reducing the event rate to about 1 kHz
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