Status of Structure Functions and Partons

The situation is summarised in Fig. 1, which shows the kinematic regions in the (x,Q) plane covered by (i) the experiments at HERA, (ii) the fixed target deep-inelastic scattering experiments and (iii) the single jet inclusive experiments at the Tevatron. Roughly speaking, the fixed target experiments determine the distributions of the u, d, ū, d̄, s, s̄ quarks for x ∼ 0.1 (and Q ∼ 10 GeV). The HERA F2 measurements determine the sea quark distributions, and their ∂F2/∂ lnQ 2 data determine the gluon, for x ∼ 10 (and Q ∼ 10 GeV). The Tevatron jet data determine the quarks and gluon distributions in a region around x ∼ 0.1 (and Q ∼ 10 GeV). In the past year new data have been available in each of the three domains. The H1 1 and ZEUS 2 experiments have measured F2 over a larger domain (see Fig. 1) with much improved precision. The D0 3 and CDF 4 collaborations have measured the inclusive single jet ET distribution and provided correlated statistical and systematic errors. In particular, the D0 experiment has measured the ET distribution in five different η bins, out to η = 3 and so samples partons in a much wider range of x (see Fig. 1). The NuTeV collaboration 5 have used ν, ν̄ beams to measure F2, xF3 with increased precision, and also, by observing μμ production, to obtain information on the s and s̄ quark distributions; CCFR have made a model-independent re-analysis 5 of their ν, ν̄ data, which removes the discrepancy for x < 0.1 with NMC. The E866 collaboration 6 have observed both pp and “pn” Drell-Yan production and further constrained the difference of the ū and d̄ distributions.