P. Abreu et al., MEASUREMENT OF THE FORWARD-BACKWARD ASYMMETRY OF E(-)-]Z-]B(B)OVER-BAR USING PROMPT LEPTONS AND A LIFETIME TAG()E(), Zeitschrift fur Physik. C, Particles and fields, 65(4), 1995, pp. 569-585
The forward-backward asymmetry of the process e(+)e(-) --> Z --> b ($)
over bar b has been measured using events collected ee by the DELPHI
experiment during the 1991 and 1992 LEP runs. This data sample corresp
onded to 884 000 hadronic Z decays at a centre-of-mass energy root s s
imilar to M(Z). The tagging of b-quark events was performed using two
approaches; the first was based on the semileptonic decay channels b -
-> X + mu and b --> X + e, the second used a lifetime tag with jet-cha
rge reconstruction. The results of these two methods were combined to
give A(FB)(b ($) over bar b) = 0.107 +/- 0.011(stat. + syst. + mixing)
. With the semileptonic sample, the forward-backward asymmetry of the
process e(+)e(-) --> Z --> c ($) over bar c was also measured to be A(
FB)(c ($) over bar c) = 0.083 +/- 0.022(stat.) +/- 0.016(syst.). The e
ffective value of the Weinberg mixing angle derived from these measure
ments was sin(2) theta(eff)(lep) = 0.2294 +/- 0.0021.