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Search for type-III seesaw heavy leptons in dilepton final states in $pp$ collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector

The ATLAS collaboration
Eur.Phys.J.C 81 (2021) 218, 2021.

Abstract
A search for the pair production of heavy leptons as predicted by the type-III seesaw mechanism is presented. The search uses proton-proton collision data at a centre-of-mass energy of 13 TeV, corresponding to 139 fb$^{-1}$ of integrated luminosity recorded by the ATLAS detector during Run 2 of the Large Hadron Collider. The analysis focuses on the final state with two light leptons (electrons or muons) of different flavour and charge combinations, with at least two jets and large missing transverse momentum. No significant excess over the Standard Model expectation is observed. The results are translated into exclusion limits on heavy-lepton masses, and the observed lower limit on the mass of the type-III seesaw heavy leptons is 790 GeV at 95% confidence level.

  • Table 1

    Data from Table 1 of auxiliary material

    10.17182/hepdata.95742.v1/t1

    Cross-sections of the type-III seesaw process for mass points used in the analysis. Branching ratios into at least two leptons...

  • Table 2

    Data from Figure 7

    10.17182/hepdata.95742.v1/t2

    Expected and observed 95 % CLs exclusion limits for the type-III seesaw process with the corresponding one- and two-standard-deviation bands,...

  • Table 3

    Data from Table 2 of auxiliary material

    10.17182/hepdata.95742.v1/t3

    Selection efficiencies in percentage relative to the events with at least two leptons for signal mass points used in the...

  • Table 4

    Data from Table 3 of auxiliary material

    10.17182/hepdata.95742.v1/t4

    Expected signal yields after each of the analysis selection cuts for the 800 GeV mass point. Total expected events represents...

  • Table 5

    Data from Figure 3a

    10.17182/hepdata.95742.v1/t5

    Distribution of $H_\text{T} + E_\text{T}^\text{miss}$ in the opposite-sign electron-electron signal region after the background-only fit.

  • Table 6

    Data from Figure 3b

    10.17182/hepdata.95742.v1/t6

    Distribution of $H_\text{T} + E_\text{T}^\text{miss}$ in the opposite-sign electron-muon signal region after the background-only fit.

  • Table 7

    Data from Figure 3c

    10.17182/hepdata.95742.v1/t7

    Distribution of $H_\text{T} + E_\text{T}^\text{miss}$ in the opposite-sign muon-muon signal region after the background-only fit.

  • Table 8

    Data from Figure 4a

    10.17182/hepdata.95742.v1/t8

    Distribution of $H_\text{T} + E_\text{T}^\text{miss}$ in the same-sign electron-electron signal region after the background-only fit.

  • Table 9

    Data from Figure 4b

    10.17182/hepdata.95742.v1/t9

    Distribution of $H_\text{T} + E_\text{T}^\text{miss}$ in the same-sign electron-muon signal region after the background-only fit.

  • Table 10

    Data from Figure 4c

    10.17182/hepdata.95742.v1/t10

    Distribution of $H_\text{T} + E_\text{T}^\text{miss}$ in the same-sign muon-muon signal region after the background-only fit.

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