The bottom quark forward-backward asymmetry ($A_{\mathrm{FB}}^b$) data at LEP exhibits a long-standing discrepancy with the standard model prediction. We propose a novel method to probe the $Zb\overline{b}$ interactions through $gg\to Zh$ production at the LHC, which is sensitive to the axial-vector component of the $Zb\overline{b}$ couplings. The apparent degeneracy of the anomalous $Zb\overline{b}$ couplings implied by the LEP precision electroweak measurements seems to be resolved by the current 13 TeV LHC $Zh$ data, which is, however, dominated by the two data points with high transverse momentum of $Z$ boson whose central values are in conflict with the standard model prediction. We also show the potential of the HL-LHC to either verify or exclude the anomalous $Zb\overline{b}$ couplings observed at LEP through measuring the $Zh$ production rate at the HL-LHC, and this conclusion is not sensitive to the possible new physics contribution induced by top quark or Higgs boson anomalous couplings in the loop.

• Received 23 January 2021
• Revised 19 June 2021
• Accepted 6 July 2021

DOI:https://doi.org/10.1103/PhysRevLett.127.051801

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Published by the American Physical Society