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 (obt ained by boosting the nonrelativistic one) to calculate analytically the sp in orientation (polarization vector and alignment tensor) of the Z boson in the processes e(+)e(-) --> ZH, e(+)e(-) --> Z gamma with arbitrarily polar ized initial beams. Due to generality of the used technique the calculated expressions for Z boson polarization and alignment contain, in general mann er, all possible spin orientation terms. Using these expressions we conside r the energy-angular spectra of the final leptons in the chains of the proc esses e(+)e(-) --> ZH, Z gamma; Z --> l(+)l(-). (C) 2000 Elsevier Science B .V. All rights reserved.