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Evidence for $t\bar{t}t\bar{t}$ production in the multilepton final state in proton–proton collisions at $\sqrt{s}=13$ $\text {TeV}$ with the ATLAS detector

The collaboration
Eur.Phys.J.C 80 (2020) 1085, 2020.

Abstract (data abstract)
A search is presented for four-top-quark production using an integrated luminosity of 139 fb$$^{-1}$$ of proton--proton collision data at a centre-of-mass energy of 13 TeV collected by the ATLAS detector at the LHC. Events are selected if they contain a same-sign lepton pair or at least three leptons (electrons or muons). Jet multiplicity, jet flavour and event kinematics are used to separate signal from the background through a multivariate discriminant, and dedicated control regions are used to constrain the dominant backgrounds. The four-top-quark production cross section is measured to be $24^{+7}_{-6}$ fb. This corresponds to an observed (expected) significance with respect to the background-only hypothesis of 4.3 (2.4) standard deviations and provides evidence for this process.

• #### Fitted cross section

10.17182/hepdata.100170.v1/t1

The results of fitted inclusive ${t\bar{t}t\bar{t}}$ cross-section

• #### Fitted $\mu$

10.17182/hepdata.100170.v1/t2

The results of the fitted signal strength $\mu$

• #### Fitted mu uncertainties

Data from Table 4

10.17182/hepdata.100170.v1/t3

List of the uncertainties in the signal strength $\mu$, grouped in categories. The quoted values are obtained by repeating the...

• #### Postfit yields

Data from Table 3

10.17182/hepdata.100170.v1/t4

Post-fit background and signal yields in the full signal region. The total systematic uncertainty differs from the sum in quadrature...

• #### Ranking

Data from Figure 4 auxiliary

10.17182/hepdata.100170.v1/t5

Ranking of the nuisance parameters included in the fit according to their impact on the signal strength $\mu$. Only the...

• #### CR HF e prefit

Data from Figure 5(a) auxiliary

10.17182/hepdata.100170.v1/t6

Comparison between data and prediction before the fit ('Pre-Fit') for the 'HF e' control region. Mat. Conv. and Low $m_{\gamma^*}$...

• #### CR HF mu prefit

Data from Figure 5(b) auxiliary

10.17182/hepdata.100170.v1/t7

Comparison between data and prediction before the fit ('Pre-Fit') for the 'HF mu' control region. Mat. Conv. and Low $m_{\gamma^*}$...

• #### CR Conv. prefit

Data from Figure 5(c) auxiliary

10.17182/hepdata.100170.v1/t8

Comparison between data and prediction before the fit ('Pre-Fit') for the $m_{ee}^{PV}$ variable in the 'Conv.' control region. The first...

• #### CR ttW prefit

Data from Figure 5(d) auxiliary

10.17182/hepdata.100170.v1/t9

Comparison between data and prediction before the fit ('Pre-Fit') for the $\Sigma p_{T}^{l}$ variable in the 'ttW' control region. The...

• #### CR HF e postfit

Data from Figure 4(a)

10.17182/hepdata.100170.v1/t10

Comparison between data and prediction after the fit ('Post-Fit') for the 'HF e' control region. Mat. Conv. and Low $m_{\gamma^*}$...

• #### CR HF mu postfit

Data from Figure 4(b)

10.17182/hepdata.100170.v1/t11

Comparison between data and prediction after the fit ('Post-Fit') for the 'HF mu' control region. Mat. Conv. and Low $m_{\gamma^*}$...

• #### CR Conv. postfit

Data from Figure 4(c)

10.17182/hepdata.100170.v1/t12

Comparison between data and prediction after the fit ('Post-Fit') for the $m_{ee}^{PV}$ variable in the 'Conv.' control region. The first...

• #### CR ttW postfit

Data from Figure 4(d)

10.17182/hepdata.100170.v1/t13

Comparison between data and prediction after the fit ('Post-Fit') for the $\Sigma p_{T}^{l}$ variable in the in 'ttW' control region....

• #### SR prefit

Data from Figure 5(e) auxiliary

10.17182/hepdata.100170.v1/t14

Comparison between data and prediction before the fit ('Pre-Fit') for the BDT score in the signal region. The first and...

• #### SR postfit

Data from Figure 3

10.17182/hepdata.100170.v1/t15

Comparison between data and prediction after the fit ('Post-Fit') for the BDT score in the signal region. The first and...