Bottom quark forward-backward asymmetry at the future electron-positron collider FCC-ee

TL;DR

The paper discusses how the future FCC-ee collider could precisely measure the bottom quark forward-backward asymmetry at the Z-pole, potentially clarifying existing discrepancies with Standard Model predictions.

Contribution

It demonstrates that FCC-ee's high luminosity will significantly reduce uncertainties in measuring A_FB^{0,b}, improving upon LEP's measurements and addressing current tensions.

Findings

FCC-ee will collect much more data at the Z-pole than LEP.

Reduced statistical uncertainties will clarify the A_FB^{0,b} discrepancy.

Potential to confirm or challenge the Standard Model prediction.

Abstract

The Standard Model (SM) prediction for the \PZ-boson pole $b$-quark forward-backward (FB) asymmetry is: $(A_{FB}^{0,b})_{th} = 0.1030 \pm 0.0002$. The LEP electron-positron collider measured instead $A_{FB}^{0,b} = 0.0992 \pm 0.0016$, value which presents the largest discrepancy with any of the SM predictions as of today. All the $A_{FB}^b$ measurements performed at LEP suffered however of an important statistical uncertainty and of different sources of systematic uncertainties. This study shows that the proposed high-luminosity electron-positron collider FCC-ee, collecting orders of magnitude more data at the \PZ-pole than LEP, will significantly reduce the statistical uncertainties on the measurement of $A_{FB}^{0,b}$, thus allowing us to shed further light on this tension.