6533b826fe1ef96bd128440c

RESEARCH PRODUCT

Tau-odd correlation on the Z0-Peak

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T-odd observables can be due either to T-violation or to unitarity corrections. We find a non-vanishing expectation value of a T-odd operator for from one-loop electroweak corrections to the resonant decay and from interference with the background. For unpolarized beams, chirality conservation allows only one relevant absorptive part of the interference between different amplitudes. We identify this unique T-odd effect as the spin correlation , where are the transverse (within the production plane) and normal (to the plane) spin components for f and , respectively. In the standard theory it is generated from the Z, W exchanges in the final vertex, from the Z-γ self-energy and from the tree-level Z-γ interference. Its value is −1.1% for e+e− → τ+τ− at 90°.