K. Ackerstaff et al., PRODUCTION OF FERMION-PAIR EVENTS IN E(-) COLLISIONS AT 161 GEV CENTER-OF-MASS ENERGY()E(), Physics letters. Section B, 391(1-2), 1997, pp. 221-234
Cross-sections for hadronic and leptonic two-fermion events, and lepto
nic forward-backward asymmetries, have been measured in e(+)e(-) colli
sions at a centre-of-mass energy of 161 GeV, using the OPAL detector a
t LEP. Results are presented both including and excluding the dominant
production of radiative gamma Z(0) events. We have measured Rb, the r
atio of the number of bb to all multihadronic events at 161 GeV, and c
ompared it to the result obtained at 130-136 GeV. All results agree we
ll with the Standard Model expectations. In a model-independent fit to
the Z(0) lineshape, the data presented here give an improved precisio
n on the gamma Z(0)-interference term The data have also been used to
obtain new limits on extensions of the Standard Model described by eff
ective four-fermion contact interactions.