  Jet substructure and differential cross sections for jets produced in the
photoproduction and deep inelastic ep scattering regimes have been measured
with the ZEUS detector at HERA using an integrated luminosity of 82.2 pb-1. The
substructure of jets has been studied in terms of the jet shape and subjet
multiplicity for jets with transverse energies Et(jet) > 17 GeV. The data are
well described by the QCD calculations. The jet shape and subjet multiplicity
are used to tag gluon- and quark-initiated jets. Jet cross sections as
functions of Et(jet), jet pseudorapidity, the jet-jet scattering angle, dijet
invariant mass and the fraction of the photon energy carried by the dijet
system are presented for gluon- and quark-tagged jets. The data exhibit the
behaviour expected from the underlying parton dynamics. A value of alphas(Mz)
of alphas(Mz) = 0.1176 +-0.0009(stat.) -0.0026 +0.0009 (exp.) -0.0072 +0.0091
(th.) was extracted from the measurements of jet shapes in deep inelastic
scattering.
