Spin polarization and alignment of the single Z boson from e+e- annihilation

We apply a formalism of the general relativistic spin-1 density matrix (obtained by boosting the nonrelativistic one) to calculate analytically the spin orientation (polarization vector and alignment tensor) of the Z boson in the processes e(+)e(-) --> ZH, e(+)e(-) --> Z gamma with arbitrarily polarized initial beams. Due to generality of the used technique the calculated expressions for Z boson polarization and alignment contain, in general manner, all possible spin orientation terms. Using these expressions we consider the energy-angular spectra of the final leptons in the chains of the processes e(+)e(-) --> ZH, Z gamma; Z --> l(+)l(-). (C) 2000 Elsevier Science B.V. All rights reserved.