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 < eta < 1.4 have been measured up to P-T = 8 GeV using the ZEUS detector. Diffractive and non-diffractive reactions have been selected with an average gamma p centre of mass (c.m.) energy of (W) = 180 GeV. For diffractive reactions, the p(T) spectra of the photon dissociation events have been measured in two intervals of the dissociated photon mass with mean values (M(X)) = 5 GeV and 10 GeV. The inclusive transverse momentum spectra fall exponentially in the low p(T) region. The non-diffractive data p show a pronounced high p(T) tail departing from the exponential shape. The p(T) 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.