Inclusive transverse momentum distributions of charged particles in diffractive and non-diffractive photoproduction at HERA

Inclusive transverse momentum spectra of charged particles in photoproduction events in the laboratory pseudorapidity range -1.2<η<1.4 have been measured up to pT=8 GeV using the ZEUS detector. Diffractive and non-diffractive reactions have been selected with an average γp centre of mass (c.m.) energy of =180 GeV. For diffractive reactions, the pT spectra of the photon dissociation events have been measured in two intervals of the dissociated photon mass with mean values =5 GeV and 10 GeV. The inclusive transverse momentum spectra fall exponentially in the low pT region. The non-diffractive data show a pronounced high pT tail departing from the exponential shape. The pT distributions are compared to lower energy photoproduction data and to hadron-hadron collisions at a similar c.m. energy. The data are also compared to the results of a next-to-leading order QCD calculation. (orig.)