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Measurement of the energy asymmetry in $t\bar{t}j$ production at 13 TeV with the ATLAS experiment and interpretation in the SMEFT framework

The ATLAS collaboration
CERN-EP-2021-181, 2021.

Abstract (data abstract)
A measurement of the energy asymmetry in jet-associated top-quark pair production is presented using $139\,\mathrm{fb}^{-1}$ of data collected by the ATLAS detector at the Large Hadron Collider during $pp$ collisions at $\sqrt{s}=13\,\text{TeV}$. The observable measures the different probability of top and antitop quarks to have the higher energy as a function of the jet scattering angle with respect to the beam axis. The energy asymmetry is measured in the semileptonic $t\bar{t}$ decay channel, and the hadronically decaying top quark must have transverse momentum above $350\,\text{GeV}$. The results are corrected for detector effects to particle level in three bins of the scattering angle of the associated jet. The measurement agrees with the SM prediction at next-to-leading-order accuracy in quantum chromodynamics in all three bins. In the bin with the largest expected asymmetry, where the jet is emitted perpendicular to the beam, the energy asymmetry is measured to be $-0.043\pm0.020$, in agreement with the SM prediction of $-0.037\pm0.003$. Interpreting this result in the framework of the Standard Model effective field theory (SMEFT), it is shown that the energy asymmetry is sensitive to the top-quark chirality in four-quark operators and is therefore a valuable new observable in global SMEFT fits.

  • Table 1

    Table 3 and Figure 7 of the paper.

    10.17182/hepdata.111348.v1/t1

    Data Measurements and predictions of the energy asymmetry in three bins of the jet angle $\theta_j$. The SM prediction was...

  • Table 2

    Section 8 of the paper.

    10.17182/hepdata.111348.v1/t2

    Correlation coefficients $\rho_{i,j}$ for the statistical and systematic uncertainties between the $i$-th and $j$-th bin of the differential $A_E$ measurement...

  • Table 3

    Figure 6 of the paper.

    10.17182/hepdata.111348.v1/t3

    The effects on the energy asymmetry of $1\sigma$ variations in its influencing nuisance parameters for the three $\theta_j$ bins. These...

  • Table 4

    Section 8 of the paper.

    10.17182/hepdata.111348.v1/t4

    Covariances $c_{ij}$ for the highest ranked systematic uncertainties in the energy asymmetry measurement differential in $\theta_j$.

  • Table 5

    Section 4 of the paper.

    10.17182/hepdata.111348.v1/t5

    Definition of the fiducial phase space with lepton candidate ($\ell$), hadronic top candidate ($j_h$), leptonic top candidate ($j_l$) and associated...

  • Table 6

    Figure 9 and Table 4 of the paper.

    10.17182/hepdata.111348.v1/t6

    Bounds on individual Wilson coefficients $C($TeV$/\Lambda)^2$ from the energy asymmetry, obtained from a combined fit to its values in all...

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