  We present a comparison of data of lepton angular distributions of
Drell-Yan/$Z$ production with the fixed-order pQCD calculations by which the
baseline of pQCD effects is illustrated. As for the $Z$ production, we predict
that $A_0$ and $A_2$ for $Z$ plus single gluon-jet events are very different
from that of $Z$ plus single quark-jet events, allowing a new experimental tool
for checking various algorithms which attempt to discriminate quark jets from
gluon jets. Using an intuitive geometric approach, we show that the violation
of the Lam-Tung relation, appearing at large transverse-momentum region, is
attributed to the presence of a non-coplanarity effect. This interpretation is
consistent with the appearance of violation beyond LO-QCD effect.
