6 research outputs found
Measurement of inelastic J / psi photoproduction at HERA
We present a measurement of the inelastic, non diffractive J/
photoproduction cross section in the reaction
with the ZEUS detector at HERA. The J/ was identified using both the
and decay channels and events were selected
within the range () for the muon (electron) decay mode,
where is the fraction of the photon energy carried by the J/ in the
proton rest frame. The cross section, the and the distributions,
after having subtracted the contributions from resolved photon and diffractive
proton dissociative processes, are given for the photon-proton centre of mass
energy range GeV; is the square of the J/ transverse
momentum with respect to the incoming proton beam direction. In the kinematic
range GeV, NLO calculations of the
photon-gluon fusion process based on the colour-singlet model are in good
agreement with the data. The predictions of a specific leading order
colour-octet model, as formulated to describe the CDF data on J/
hadroproduction, are not consistent with the data.Comment: 31 pages including 7 figure