Abstract

A search for pair production of doubly charged Higgs bosons ($H^{\pm \pm}$), each decaying into a pair 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 an integrated luminosity of 139 fb$^{-1}$ recorded by the ATLAS detector during Run 2 of the Large Hadron Collider. This analysis focuses on same-charge leptonic decays, $H^{\pm \pm} \rightarrow \ell^{\pm} \ell^{\prime \pm}$ where $\ell, \ell^\prime=e, \mu, \tau$, in two-, three-, and four-lepton channels, but only considers final states which include electrons or muons. No evidence of a signal is observed. Corresponding limits on the production cross-section and consequently a lower limit on $m(H^{\pm \pm})$ are derived at 95% confidence level. Assuming that the branching ratios to each of the possible leptonic final states are equal, $\mathcal{B}(H^{\pm \pm} \rightarrow e^\pm e^\pm) = \mathcal{B}(H^{\pm \pm} \rightarrow e^\pm \mu^\pm) = \mathcal{B}(H^{\pm \pm} \rightarrow \mu^\pm \mu^\pm) = \mathcal{B}(H^{\pm \pm} \rightarrow e^\pm \tau^\pm) = \mathcal{B}(H^{\pm \pm} \rightarrow \mu^\pm \tau^\pm) = \mathcal{B}(H^{\pm \pm} \rightarrow \tau^\pm \tau^\pm) = 1/6$, the observed lower limit on the mass of a doubly charged Higgs boson is 1080 GeV within the left-right symmetric type-II seesaw model, which is an improvement over previous limits. Additionally, a lower limit of $m(H^{\pm \pm})$ = 900 GeV is obtained in the context of the Zee-Babu neutrino mass model.

Table 1

Data from Table 1 of auxiliary material

10.17182/hepdata.138987.v1/t1

LO, NLO cross-sections and K-factors for the pair-production of doubly charged Higgs bosons in pp collisions at $\sqrt{s}$ = 13...
Table 2

Data from Figure 8

10.17182/hepdata.138987.v1/t2

Observed (solid line) and expected (dashed line) 95% CL upper limits on the $H^{\pm\pm}$ pair production cross-section as a function...
Table 3

Data from Figure 6a

10.17182/hepdata.138987.v1/t3

Distribution of $m(e^{\pm},e^{\pm})_{\mathrm{lead}}$ in the electron-electron signal region after the background-only fit.
Table 4

Data from Figure 6b

10.17182/hepdata.138987.v1/t4

Distribution of $m(e^{\pm},\mu^{\pm})_{\mathrm{lead}}$ in the electron-muon signal region after the background-only fit.
Table 5

Data from Figure 6c

10.17182/hepdata.138987.v1/t5

Distribution of $m(\mu^{\pm},\mu^{\pm})_{\mathrm{lead}}$ in the muon-muon signal region after the background-only fit.
Table 6

Data from Figure 7a

10.17182/hepdata.138987.v1/t6

Distribution of $m(\ell^{\pm},\ell^{\prime \pm})_{\mathrm{lead}}$ in the three-lepton signal region after the background-only fit.
Table 7

Data from Figure 7b

10.17182/hepdata.138987.v1/t7

Event yield in the four-lepton signal region after the background-only fit.
Table 8

Data from Table 3 of auxiliary material

10.17182/hepdata.138987.v1/t8

Two-lepton signal region weighted cutflows for electron-electron channel. Data and a few representative signal samples are presented alongside the main...
Table 9

Data from Table 3 of auxiliary material

10.17182/hepdata.138987.v1/t9

Two-lepton signal region weighted cutflows for electron-muon channel. Data and a few representative signal samples are presented alongside the main...
Table 10

Data from Table 3 of auxiliary material

10.17182/hepdata.138987.v1/t10

Two-lepton signal region weighted cutflows for muon-muon channel. Data and a few representative signal samples are presented alongside the main...
Table 11

Data from Table 4 of auxiliary material

10.17182/hepdata.138987.v1/t11

Three-lepton signal region weighted cutflow for $\ell \ell \ell$ channel. Data and a few representative signal samples are presented alongside...
Table 12

Data from Table 5 of auxiliary material

10.17182/hepdata.138987.v1/t12

Four-lepton signal region weighted cutflow for $\ell \ell \ell \ell$ channel. Data and a few representative signal samples are presented...

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