Anomalous Zbb[over ¯] Couplings: From LEP to LHC

The bottom quark forward-backward asymmetry (A_{FB}^{b}) data at LEP exhibits a long-standing discrepancy with the standard model prediction. We propose a novel method to probe the Zbb[over ¯] interactions through gg→Zh production at the LHC, which is sensitive to the axial-vector component of the Zbb[over ¯] couplings. The apparent degeneracy of the anomalous Zbb[over ¯] 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 Zbb[over ¯] 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.