Spin alignment in heavy and light flavour systems at OPAL

Spin alignment of inclusive vector mesons and longitudinal polarization of Lambda hyperons have been measured in a sample of 4.3 million hadronic Z(0) decays from the OPAL detector at LEP. Leading, light vector mesons have be en found to populate preferentially the helicity-zero state, a result which has no firm theoretical explanation. The values of off-diagonal elements o f the helicity density matrix are in agreement with a theory based on the S tandard Model with coherent fragmentation. The longitudinal polarization of the Lambda is well described by a model in which the constituent strange q uark carries all of the hyperon spin.