Measurements of the b quark forward-backward asymmetry around the Z $^0$ peak using jet charge and vertex charge

Abstract

The b quark forward-backward asymmetry has been measured using approximately four million hadronic Z 0 decays collected with the OPAL detector at LEP. Both jet charge and vertex charge were used to estimate whether the b quark was produced in the forward or backward thrust hemisphere. The measured values corrected to the hadronlevel thrust axis are A b FB = 0.041 ±0.021 ±0.002 √ s = 89.44 GeV A b FB = 0.0994 ±0.0052 ±0.0044 √ s = 91.21 GeV A b FB = 0.145 ±0.017 ±0.007 √ s = 92.91 GeV where in each case the first error is statistical and the second systematic. Within the framework of the Standard Model these measurements correspond to an effective weak mixing angle of sin 2 θ eff,e W = 0.2308 ± 0.0013. The measurements are in agreement with the Standard Model and other measurements at LEP.

Review of the Weak Mixing Angle Results with Heavy Quarks at LEP and SLC

“…The distance between the primary and the secondary vertex divided by its corresponding error is used as tagging variable. The lifetime inside b events leads to well separated vertices as pictured in Fig.5 [13]. The third approach was developed from the impact parameter method.…”

“…While DELPHI and OPAL are using the integral ansatz and perform only a fit in the angle. ALEPH uses in addition the information of the different κ values [4,7,11,13,15,19].…”

The International Linear Collider

“…Jet-charge and vertex-charge reconstruction allows then to tell the quark from the antiquark produced in the same event. 89,90 Similarly to LEP and SLC analyses, the forward-backward asymmetry can be obtained from a fit to the flow of the jet charge Q jet , defined as…”