Triple gauge couplings in polarised $e^-e^+ \rightarrow W^-W^+$ and their measurement using optimal observables

Abstract.

The sensitivity of optimal integrated observables to electroweak triple gauge couplings is investigated for the process $e^-e^+ \rightarrow W^-W^+ \rightarrow 4$ fermions at future linear colliders. By a suitable reparameterisation of the couplings we achieve that all 28 coupling parameters have uncorrelated statistical errors and are naturally normalised for this process. Discrete symmetry properties simplify the analysis and allow checks on the stability of numerical results. We investigate the sensitivity to the couplings of the normalised event distribution and the additional constraints that can be obtained from the total rate. Particular emphasis is put on the gain in sensitivity one can achieve with longitudinal beam polarisation. We also point out questions that may best be settled with transversely polarised beams. In particular we find that with purely longitudinal polarisation one linear combination of coupling parameters is hardly measurable by means of the normalised event distribution.