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

Area of Science:

• High Energy Physics
• Particle Physics
• Standard Model Physics

Background:

• The bottom quark forward-backward asymmetry (A_{FB}^{b}) at LEP shows a persistent deviation from Standard Model predictions.
• Precision electroweak measurements at LEP suggest an apparent degeneracy in anomalous Zbb couplings.

Purpose of the Study:

• To propose and analyze a novel method for probing Zbb interactions via gg→Zh production at the LHC.
• To investigate the sensitivity of this process to the axial-vector component of Zbb couplings.
• To assess the potential of current and future LHC data to resolve anomalous couplings and probe new physics.

Main Methods:

• Analysis of gg→Zh production at the LHC as a probe for Zbb interactions.
• Examination of current 13 TeV LHC Zh data, particularly focusing on high transverse momentum Z boson events.
• Projection of the potential of the High-Luminosity LHC (HL-LHC) to measure Zh production rates.

Main Results:

• Current 13 TeV LHC Zh data, while dominated by high transverse momentum Z boson events, shows central values conflicting with the Standard Model.
• These results suggest a potential resolution to the degeneracy observed in anomalous Zbb couplings from LEP data.
• The HL-LHC has significant potential to either confirm or exclude the anomalous Zbb couplings observed at LEP.

Conclusions:

• Measuring Zh production rates at the HL-LHC offers a robust method to test anomalous Zbb couplings.
• This analysis is shown to be insensitive to potential new physics contributions from anomalous top quark or Higgs boson couplings in the loop.
• The study highlights the LHC's capability to address long-standing discrepancies in electroweak measurements and probe beyond Standard Model physics.