The weak dipole moments of leptons and quarks, \ie those related to their \(Z\)--coupling, are reviewed. Standard Model predictions and experimental results may result in a stringent test for both ...their pointlike structure and also for the Standard Model. Special attention is devoted to the anomalous weak--magnetic dipole moment and to the \(CP\)--violating weak--electric dipole moment.
We show that coherent \(\eta\) and \(\etap\) photoproduction by means of the Primakoff Effect on the proton depends on the strange component of the neutral axial current coupling. We construct ...polarization asymmetries that are sensitive to this coupling through the \(\gamma - Z\) interference. The \(\eta^\prime\) is not a Goldstone boson of a spontaneously broken chiral symmetry, but a phenomenological analysis of the \(\eta\) and \(\eta^\prime\) production through chiral perturbation theory allows to calculate the observables of interest. The polarized proton or polarized photon asymmetries are predicted to be close to \(10^{-4}\) for \(-q^2 \sim 0.1-0.5\;\mbox{\rm GeV}^2\).
We calculate the prediction for the anomalous weak-magnetic form factor of the tau lepton at \(q^2=M_Z^2\) within the Standard Model. With all particles on-shell, this is a electroweak gauge ...invariant quantity. Its value is \(a_\tau^w (M_Z^2)= - \;(2.10 + 0.61\, i) \times 10^{-6}\). We show that the transverse and normal components of the single-tau polarization of tau pairs produced at \(e^+e^-\) unpolarized collisions are sensitive to the real and absorptive parts of the anomalous weak-magnetic dipole moment of the tau. The sensitivity one can achieve at LEP in the measurement of this dipole moment is discussed.
We show that transverse and normal single-\(tau\) polarization of \(tau\) pairs produced at \(e^+\) \(e^-\) unpolarized collisions, at the \(Z\) peak, are sensitive to weak (magnetic and electric) ...dipole moments of the \(tau\). We also show how these components of the \(\tau\) polarization are accessible by measuring appropriate azimuthal asymmetries in the angular distribution of its decay products. Sensitivities of the order of \(10^{-18}\) \(e\cdot cm\), for the weak-electric dipole moment, and \(10^{-4}\) (\(10^{-3}\)), for the real (imaginary) part of the weak-magnetic dipole moment of \(\tau\), may be achieved. Compatible bounds are also presented from spin-spin correlated asymmetries.
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