Professor Amanda Cooper-Sarkar

Abstract:

Exclusive production of ρ⁰ and J/ψ mesons in e⁺p collisions has been studied with the ZEUS detector in the kinematic range 0.25 < Q² < 50 GeV², 20 < W < 167 GeV for the ρ⁰ data and 2 < Q² < 40 GeV², 50 < W < 150 GeV for the J/ψ data. Cross sections for exclusive ρ⁰ and J/ψ production have been measured as a function of Q², W and t. The spin-density matrix elements r⁰⁴ 00, r¹ 1-1i and Re r⁵ 10 have been determined for exclusive ρ⁰ production as well as r⁰⁴ 00 and r⁰⁴ 1-1 for exclusive J/ψ production. The results are discussed in the context of theoretical models invoking soft and hard phenomena.

Abstract:

The inclusive forward jet cross section in deep inelastic e+p scattering has been measured in the region of cursive Greek chi-Bjorken, 4.5 · 10-4 to 4.5 · 10-2. This measurement is motivated by the search for effects of BFKL-like parton shower evolution. The cross section at hadron level as a function of cursive Greek chi is compared to cross sections predicted by various Monte Carlo models. An excess of forward jet production at small cursive Greek chi is observed, which is not reproduced by models based on DGLAP parton shower evolution. The Colour Dipole model describes the data reasonably well. Predictions of perturbative QCD calculations at the parton level based on BFKL and DGLAP parton evolution are discussed in the context of this measurement.