Professor Amanda Cooper-Sarkar

Abstract:

A short personal account is given of the impact of HERA data and the influence of Jan Kwiecinski on low x physics.

Abstract:

Events with a final-state proton carrying a large fraction of the proton beam momentum, x L >0.6, and the square of the transverse momentum p T ² <0.5 GeV ² , have been studied in e ⁺ p collisions with the ZEUS detector at HERA. Data with different photon virtualities were used: Q ² <0.02 GeV ² , 0.12 <0.74 GeV ² and 32 <254 GeV ² , corresponding to integrated luminosities of 0.9, 1.85 and 3.38 pb ^-1 . The cross sections are given as a function of x L , p T ² , Q ² and the Bjorken scaling variable, x. The ratio of the cross section for leading proton production to the inclusive e ⁺ p cross section shows only a mild dependence on Q ² and on x. In the region 0.6L <0.97, the relative yield of protons is only a weak function of x L . © 2003 Elsevier Science B.V. All rights reserved.