Search for leptonic charge asymmetry in $t\bar{t}W$ production in final states with three leptons at $\sqrt{s} = 13$ TeV

The ATLAS collaboration
JHEP 07 (2023) 033, 2023.

Abstract
A search for the leptonic charge asymmetry ($A_\text{c}^{\ell}$) of top-quark$-$antiquark pair production in association with a $W$ boson ($t\bar{t}W$) is presented. The search is performed using final states with exactly three charged light leptons (electrons or muons) and is based on $\sqrt{s} = 13$ TeV proton$-$proton collision data collected with the ATLAS detector at the Large Hadron Collider at CERN during the years 2015$-$2018, corresponding to an integrated luminosity of 139 fb$^{-1}$. A profile-likelihood fit to the event yields in multiple regions corresponding to positive and negative differences between the pseudorapidities of the charged leptons from top-quark and top-antiquark decays is used to extract the charge asymmetry. At reconstruction level, the asymmetry is found to be $-0.123 \pm 0.136$ (stat.) $\pm \, 0.051$ (syst.). An unfolding procedure is applied to convert the result at reconstruction level into a charge-asymmetry value in a fiducial volume at particle level with the result of $-0.112 \pm 0.170$ (stat.) $\pm \, 0.054$ (syst.). The Standard Model expectations for these two observables are calculated using Monte Carlo simulations with next-to-leading-order plus parton shower precision in quantum chromodynamics and including next-to-leading-order electroweak corrections. They are $-0.084 \, ^{+0.005}_{-0.003}$ (scale) $\pm\, 0.006$ (MC stat.) and $-0.063 \, ^{+0.007}_{-0.004}$ (scale) $\pm\, 0.004$ (MC stat.) respectively, and in agreement with the measurements.

  • Results

    10.17182/hepdata.140938.v1/t1

    Measured values of the leptonic charge asymmetry ($A_c^{\ell}$) in ttW production in the three lepton channel. Results are given at...

  • Fiducial phase-space definition

    Section 9

    10.17182/hepdata.140938.v1/t2

    Definition of the fiducial phase space at particle level with the light lepton candidates $(\ell=e,\mu)$, jets ($j$) and invariant mass...

  • Nuisance Parameter correlation matrix

    Additional material

    10.17182/hepdata.140938.v1/t3

    Correlation matrix between the Normalisation Factors and the Nuisance Parameters (NP) in the fit using using both statistical and systematic...

  • Norm. Factor values for stat only fit

    Additional material

    10.17182/hepdata.140938.v1/t4

    Normalisation factors for the major background processes and ttW ($\Delta \eta < 0$) from the fit using only statistical uncertainties...

  • Norm. Factor values for stat+syst fit

    Figure 5

    10.17182/hepdata.140938.v1/t5

    Normalisation factors for the major background processes and ttW ($\Delta \eta < 0$) from the fit using using both statistical...

  • Nuisance Parameter correlation matrix Stat only

    Additional material

    10.17182/hepdata.140938.v1/t6

    Correlation matrix between the Normalisation Factors in the fit using only statistical uncertainties (fixing Nuisance Parameters (NP) to their fitted...

  • Nuisance Parameter ranking plot for $A_c^{\ell}$

    Figure Aux 01

    10.17182/hepdata.140938.v1/t7

    The most relevant systematic uncertainties ranked by their impact on the leptonic charge asymmetry ($A_c^{\ell}$) parameter at reconstructed level. The...

  • Nuisance Parameter ranking plot for ttW NF ($\Delta \eta < 0$)

    Additional material

    10.17182/hepdata.140938.v1/t8

    The most relevant systematic uncertainties ranked by their impact on the ttW Normalisation Factor ($\Delta \eta < 0$) parameter at...

  • Prefit yield table

    Table 2

    10.17182/hepdata.140938.v1/t9

    The predicted and observed numbers of events in the control and signal regions. The predictions are shown before the fit...

  • Postfit yield table

    Table 3

    10.17182/hepdata.140938.v1/t10

    The predicted and observed numbers of events in the control and signal regions. The predictions are shown after the fit...

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