Professor Amanda Cooper-Sarkar

Abstract:

Based on a QCD analysis of the parton momentum distributions in the proton, the ratio rv=dv/uv of the d and u valence quark distributions is determined as function of x in the range 0.01v mainly depends on the deuterium/hydrogen ratios of the normalised x-y-Q²-distributions many systematic effects cancel. It is found that rv decreases with increasing x, and drops below the naive SU(6) expectation of 0.5 for x≳0.3. An extrapolation of rv to x=1 is consistent with the hypothesis rv(1)=0. © 1994 Springer-Verlag.

Abstract:

Energy flows in deep inelastic electron-proton scattering are investigated at a centre-of-mass energy of 269 GeV for the range Q2 ≥ 10 GeV2 using the ZEUS detector. A comparison is made between events with and without a large rapidity gap between the hadronic system and the proton direction. The energy flows, corrected for detector acceptance and resolution, are shown for these two classes of events in both the HERA laboratory frame and the Breit frame. From the differences in the shapes of these energy flows we conclude that QCD radiation is suppressed in the large-rapidity-gap eents compared to the events without a large rapidity gap. © 1994.

Abstract:

Photon proton cross sections for elastic light vector meson production, σel^νp, inelastic diffractive production, σnd^νp, non-diffractive production, σd^νp, as well as the total cross section, σtot^νp, have been measured at an average υp center of mass energy of 180 GeV with the ZEUS detector at HERA. The resulting values are σel^νp = 18 ± 7 μb, σd^νp = 33 ± 8 μb, σnd^νp = 91 ± 11 μb, and σtot^νp 143 ± 17 μb, where the errors include statistical and systematic errors added in quadrature. © 1994 Springer-Verlag.