Tests of the standard model and constraints on new physics from measurements of fermion pair production at 130-GeV to 172-GeV at LEP

Production of events with hadronic and leptonic final states has been measured in e^+e^- collisions at centre-of-mass energies of 130-172 GeV, using the OPAL detector at LEP. Cross-sections and leptonic forward-backward asymmetries are presented, both including and excluding the dominant production of radiative Z \gamma events, and compared to Standard Model expectations. The ratio R_b of the cross-section for bb(bar) production to the hadronic cross-section has been measured. In a model-independent fit to the Z lineshape, the data have been used to obtain an improved precision on the measurement of \gamma-Z interference. The energy dependence of \alpha_em has been investigated. The measurements have also been used to obtain limits on extensions of the Standard Model described by effective four-fermion contact interactions, to search for t-channel contributions from new massive particles and to place limits on chargino pair production with subsequent decay of the chargino into a light gluino and a quark pair.

Note:

68 pages, LaTeX, uses a4p.sty and pennames.sty, 23 eps figures included, submitted to Zeit. Phys. C Report-no: CERN-PPE/97-101

electron positron: colliding beams
electron positron: annihilation
fermion: pair production
bottom
channel cross section: ratio
Z0: width
interference: (Z0 photon)
coupling constant: electromagnetic interaction
energy dependence
four-fermion interaction

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