Spin alignment of leading K*(892)0 mesons in hadronic Z0 decays

Abstract

Helicity density matrix elements for inclusive K*(892)0 mesons from hadronic Z0 decays have been measured over the full range of K*0 momentum using data taken with the OPAL experiment at LEP. A preference for occupation of the helicity zero state is observed at all scaled momentum xp values above 0.3, with the matrix element ρ00 rising to 0.66 ± 0.11 for xp > 0.7. The values of the real part of the off-diagonal element ρ1-1 are negative at large xp, with a weighted average value of -0.09 ± 0.03 for xp > 0.3, in agreement with new theoretical predictions based on Standard Model parameters and coherent fragmentation of the qq system from the Z0 decay. All other helicity density matrix elements..