LEP 1 Heavy Flavour Electroweak Physics and 2-Fermion Processes at LEP 2

TL;DR

This paper reviews heavy flavour electroweak measurements at LEP1 and 2-fermion process results at LEP2, highlighting key asymmetry measurements, their implications for electroweak parameters, and constraints on new physics beyond the Standard Model.

Contribution

It provides a comprehensive analysis of heavy quark asymmetries and decay widths at LEP, and sets limits on new physics using LEP2 data, with a focus on electroweak parameters and discrepancies.

Findings

Measured heavy quark asymmetries used to determine sin^2(theta_eff^lept)

Observed a 2.9 sigma discrepancy between A_l^SLD and A_FB^b measurements

All LEP2 measurements align with Standard Model predictions and set limits on beyond Standard Model physics.

Abstract

Results from heavy flavour electroweak physics at LEP1 are reviewed together with measurements of 2-fermion processes at LEP2. For the former measurements the emphasis is on analyses of heavy quark forward-backward asymmetries, A_FB^b,c, and on the partial decay widths of the Z^0 to heavy quarks, R_b,c. The measurements of the heavy quark asymmetries are used to extract the effective electroweak mixing angle for leptons, sin^2(theta_eff^lept). A 2.9 sigma discrepancy between measurements of this quantity from A_l^SLD and from A_FB^b is observed. The 2-fermion processes at LEP2 are used to place stringent limits on physics processes beyond the Standard Model. However, all measured quantities are in reasonable agreement with the Standard Model expectations, and all calculated limits are well above the highest LEP2 center-of-mass energies.