EXTRACTION OF THE GLUON DENSITY OF THE PROTON AT X RID B-9165-2008 RID C-5889-2009 RID A-4818-2008 RID C-1693-2008

The gluon momentum density xg(x, Q(2)) of the proton was extracted at Q(2) = 20 GeV2 for small values of x between 4 x 10(-4) and 10(-2) from the scaling violations of the proton structure function F-2 measured recently by ZEUS in deep inelastic neutral current ep scattering at HERA. The extraction was performed in two ways. Firstly, using a global NLO fit to the ZEUS data on F-2 at low x constrained by measurements from NMC at larger x; and secondly using published approximate methods for the solution of the GLAP QCD evolution equations. Consistent results are obtained. A substantial increase of the gluon density is found at small x in comparison with the NMC result obtained at larger values of x

MEASUREMENT OF TOTAL AND PARTIAL PHOTON PROTON CROSS-SECTIONS AT 180 GEV CENTER-OF-MASS ENERGY RID C-1693-2008 RID B-9165-2008 RID C-5889-2009 RID A-4818-2008

Photon proton cross sections for elastic light vector meson production, sigma(el)gammap, inelastic diffractive production, sigma(d)gammap, non-diffractive production, sigma(nd)gammap, as well as the total cross section, sigma(tot)gammap, have been measured at an average gammap center of mass energy of 180 GeV with the ZEUS detector at HERA. The resulting values are sigma(el)gammap = 18 +/- 7 mub, sigma(d)gammap = 33 +/- 8 mub, sigma(nd)gammap = 91 +/- 11 mub, and sigma(tot)gammap = 143 +/- 17 mub, where the errors include statistical and systematic errors added in quadrature