  The distribution of the azimuthal angle for the charged hadrons has been
studied in the hadronic centre-of-mass system for neutral current deep
inelastic positron-proton scattering with the ZEUS detector at HERA.
Measurements of the dependence of the moments of this distribution on the
transverse momenta of the charged hadrons are presented. Asymmetries that can
be unambiguously attributed to perturbative QCD processes have been observed
for the first time.
