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Gauge Invariance and the Unstable Particle

Robin G. Stuart

hep-pharXiv:hep-ph/9706550

Abstract

It is shown how to construct exactly gauge-invariant S-matrix elements for processes involving unstable gauge particles such as the Z0 boson. The results are applied to derive a physically meaningful expression for the cross-section σ(e+e- Z0Z0) and thereby provide a solution to the long-standing problem of the unstable particle.

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