Low x Physics at HERA

Abstract

With a center of mass energy of about 300 GeV, the electron proton collider HERA makes possible the exploration of the kinematic region of very low x, i.e. x ≤ 10¯³. Here and in the following, x denotes the fraction of the proton’s momentum carried by the quark that interacts with the electron. At low x, the struck quark usually results from a long cascade of parton branchings as illustrated in Fig. 1. Partons at the bottom of the cascade can carry a fraction

on behalf of the Hl and ZEUS collaborations