Abstract
Four-fermion final states qq̄e+e− and qq̄μ+μ− from neutral-current interactions in e+e− collisions are studied in the OPAL detector at LEP at centre-of-mass energies from 183 GeV to 209 GeV. The data analysed correspond to a total integrated luminosity of about 650 pb−1 recorded from 1997 to 2000. Corresponding to the acceptance of the OPAL detector, a signal definition is applied requiring both leptons to have a scattering angle satisfying |cosθ|<0.95. Further requirements are made on the invariant masses of the fermion pairs. The extracted cross-sections for the processes e+e−→qq̄e+e− and e+e−→qq̄μ+μ− are consistent with the expectations from the Standard Model.
Highlights
Four-fermion processes in e+e− collisions have proven to be an important tool for studying the validity of √the Standard Model and looking for signs of physics beyond
The cross-sections for these two processes are characterized by a steep increase near threshold. They have been measured by restricting the invariant masses of pairs of fermions to the W or Z mass, thereby selecting only some of all possible four-fermion final states
In this paper we describe a selection for qqe+e− and qqμ+μ− final states that is sensitive to all invariant masses of fermion pairs
Summary
Four-fermion processes in e+e− collisions have proven to be an important tool for studying the validity of √the Standard Model and looking for signs of physics beyond. The cross-sections for these two processes are characterized by a steep increase near threshold They have been measured by restricting the invariant masses of pairs of fermions to the W or Z mass, thereby selecting only some of all possible four-fermion final states. It is interesting to extend the measurement into regions where the invariant masses of the fermion-pairs are not as restricted Results on this have been reported from the LEP experiments for centre-of-mass energies up to 183 GeV [3]. In about 650 pb−1 of data recorded with the OPAL detector in the years 1997 to 2000 at centre-of-mass energies between 183 GeV and 209 GeV, the cross-sections for the processes e+e− → qqe+e− and e+e− → qqμ+μ− are measured within the kinematic bounds described above. After a description of the systematic studies, the measured cross-sections are given, together with a discussion of the results
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