Probing the Zbb coupling at the Z-pole of future lepton colliders

2023/07/16 by Bin Yan, Yan, Bin, C.–P. Yuan +3
Physics and Astronomy · Engineering · #Particle physics theoretical and experimental studies #Particle Detector Development and Performance #Superconducting Materials and Applications

paper · pdf · doi:10.48550/arxiv.2307.08014

Abstract

The determination of the Zbb coupling in experiments has been a long-standing challenge, as the limited precision of off Z-pole measurements at the LEP has resulted in two degenerate solutions remained to be resolved. In this paper, we propose a novel method to probe the Zbb coupling by measuring the forward-backward asymmetry of the bottom quark, A^b_FB, in the bb system of the e⁺ e^- → b b γ and/or e⁺ e^- → b b g processes at the Z-pole of future lepton colliders. The additional hard photon or light jet radiation can mimic the energy scanning of the e⁺e^-→ bb process, and the A_{\rm FB}^b distribution from the γ-Z interference process is linearly sensitive to the Zbb coupling. By combining the expected measurements of R⁰_b and A^0,b_FB at the Z-pole at the CEPC, the A^b_FB distributions can break the degeneracy observed at the LEP, leading to a unique determination of the Zbb coupling through Z-pole running alone.

Related

• Complementary constraints on Zbb couplings at the LHC
• Determination of the first-generation quark couplings at the Z-pole
• Revised QCD effects on the Z→ bb forward-backward asymmetry in e⁺e^- collisions
• New Physics Off the Z-Pole: e⁺ e^- → f f at Future Lepton Colliders
• Lepton and quark asymmetries