G. Abbiendi et al., Tests of the standard model and constraints on new physics from measurements of fermion-pair production at 189 GeV at LEP, EUR PHY J C, 13(4), 2000, pp. 553-572
Cross-sections and angular distributions for hadronic and lepton pair final
states in e(+) e(-) collisions at a centre-of-mass energy near 189 GcV. me
asured with the OPAL detector at LEP. are presented and compared with the p
redictions of the Standard Model. The results are used to measure the energ
y dependence of the electromagnetic coupling constant alpha(em), and to pla
ce limits: on new physics as described by four-fermion contact interactions
or bq the exchange of a new heavy particle such as a sneutrino in super sy
mmetric theories with R-parity violation. A search for the indirect effects
of the gravitational interaction in extra dimensions on the mu(+)mu(-) and
tau(+)tau(-) final states ia also presented.