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Search for heavy lepton resonances decaying to a $Z$ boson and a lepton in $pp$ collisions at $\sqrt{s}=8$ TeV with the ATLAS detector

The collaboration
JHEP 1509 (2015) 108, 2015

Abstract (data abstract)
CERN-LHC. A search for heavy leptons decaying to a $Z$ boson and an electron or a muon is presented. The search is based on $pp$ collision data taken at $\sqrt{s}=8$ TeV by the ATLAS experiment at the CERN Large Hadron Collider, corresponding to an integrated luminosity of 20.3 fb$^{-1}$. Three high-transverse-momentum electrons or muons are selected, with two of them required to be consistent with originating from a $Z$ boson decay. No significant excess above Standard Model background predictions is observed, and 95% confidence level limits on the production cross section of high-mass trilepton resonances are derived. The results are interpreted in the context of vector-like lepton and type-III seesaw models. For the vector-like lepton model, most heavy lepton mass values in the range 114-176 GeV are excluded. For the type-III seesaw model, most mass values in the range 100-468 GeV are excluded.

• #### Table 1

Data from Figure 3 a

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The $\delta m=m_{3\ell}-m_{ell^+\ell^-}$ distributions for the $4\ell$ category and $Z+e$ flavor channel.

• #### Table 2

Data from Figure 3 b

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The $\delta m=m_{3\ell}-m_{ell^+\ell^-}$ distributions for the $4\ell$ category and $Z+\mu$ flavor channel.

• #### Table 3

Data from Figure 3 c

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The $\delta m=m_{3\ell}-m_{ell^+\ell^-}$ distributions for the $3\ell+jj$ category and $Z+e$ flavor channel.

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Data from Figure 3 d

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The $\delta m=m_{3\ell}-m_{ell^+\ell^-}$ distributions for the $3\ell+jj$ category and $Z+\mu$ flavor channel.

• #### Table 5

Data from Figure 3 e

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The $\delta m=m_{3\ell}-m_{ell^+\ell^-}$ distributions for the $3\ell$-only category and $Z+e$ flavor channel.

• #### Table 6

Data from Figure 3 f

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The $\delta m=m_{3\ell}-m_{ell^+\ell^-}$ distributions for the $3\ell$-only category and $Z+\mu$ flavor channel.

• #### Table 7

Data from Figure 5 a

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95\% CL upper limits on the vector-like lepton cross section, for heavy vector-like leptons coupling exclusively to electrons.

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Data from Figure 5 b

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95\% CL upper limits on the vector-like lepton cross section, for heavy vector-like leptons coupling exclusively to muons.

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Data from Figure 6 a

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95% CL upper limits on the type-III seesaw production cross section, for the seesaw leptons coupling exclusively to electrons.

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Data from Figure 6 b

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95% CL upper limits on the type-III seesaw production cross section, for the seesaw leptons coupling exclusively to muons.

• #### Table 11

Data from Figure 7 a

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95% CL upper limits on $\sigma_{\mathrm{vis}}$ for the $Z+e$ flavour channel, derived without dividing events into the three categories.

• #### Table 12

Data from Figure 7 b

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95% CL upper limits on $\sigma_{\mathrm{vis}}$ for the $Z+\mu$ flavour channel, derived without dividing events into the three categories.

• #### Table 13

Data from Figure 7 a (auxiliary)

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95% CL upper limits on $\sigma_{\mathrm{vis}}$ for the $Z+e$ flavour channel, for events in the four lepton signal region.:.

• #### Table 14

Data from Figure 7 b (auxiliary)

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95% CL upper limits on $\sigma_{\mathrm{vis}}$ for the $Z+\mu$ flavour channel, for events in the four lepton signal region.

• #### Table 15

Data from Figure 8 a (auxiliary)

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95% CL upper limits on $\sigma_{\mathrm{vis}}$ for the $Z+e$ flavour channel, for events in the two-jet signal region.

• #### Table 16

Data from Figure 8 b (auxiliary)

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95% CL upper limits on $\sigma_{\mathrm{vis}}$ for the $Z+\mu$ flavour channel, for events in the two-jet signal region.

• #### Table 17

Data from Figure 9 a (auxiliary)

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Efficiencies for reconstructing and correctly identifying the $L^{\pm}\rightarrow Z(\ell\ell)e^{\pm}$ decay in the inclusive category and $Z+e$ flavor channel, for events...

• #### Table 18

Data from Figure 9 b (auxiliary)

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Efficiencies for reconstructing and correctly identifying the $L^{\pm}\rightarrow Z(\ell\ell)\mu^{\pm}$ decay in the inclusive category and $Z+\mu$ flavor channel, for events...

• #### Table 19

Data from Figure 10 a (auxiliary)

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Efficiencies for reconstructing and correctly identifying the $L^{\pm}\rightarrow Z(\ell\ell)e^{\pm}$ decay in the $4\ell$ category and $Z+e$ flavor channel, for events...

• #### Table 20

Data from Figure 10 b (auxiliary)

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Efficiencies for reconstructing and correctly identifying the $L^{\pm}\rightarrow Z(\ell\ell)\mu^{\pm}$ decay in the $4\ell$ category and $Z+\mu$ flavor channel, for events...

• #### Table 21

Data from Figure 11 a (auxiliary)

10.17182/hepdata.69501.v1/t21

Efficiencies for reconstructing and correctly identifying the $L^{\pm}\rightarrow Z(\ell\ell)e^{\pm}$ decay in the $3\ell+jj$ category and $Z+e$ flavor channel, for events...

• #### Table 22

Data from Figure 11 b (auxiliary)

10.17182/hepdata.69501.v1/t22

Efficiencies for reconstructing and correctly identifying the $L^{\pm}\rightarrow Z(\ell\ell)\mu^{\pm}$ decay in the $3\ell+jj$ category and $Z+\mu$ flavor channel, for events...

• #### Table 23

Data from Figure 12 a (auxiliary)

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Efficiencies for reconstructing and correctly identifying the $L^{\pm}\rightarrow Z(\ell\ell)e^{\pm}$ decay in the $3\ell$-only category and $Z+e$ flavor channel, for events...

• #### Table 24

Data from Figure 12 b (auxiliary)

10.17182/hepdata.69501.v1/t24

Efficiencies for reconstructing and correctly identifying the $L^{\pm}\rightarrow Z(\ell\ell)\mu^{\pm}$ decay in the $3\ell$-only category and $Z+\mu$ flavor channel, for events...