Summary of Dis 2000

We summarize the experimental and theoretical results presented in the " Physics at the Highest Q 2 and p 2 t " working group at the DIS 2000 Workshop. High Q 2 and p 2 t processes measured at current and future colliders allow to improve our knowledge of Standard Model (SM) physics, by providing precise measurements of the SM parameters and, consequently, consistency checks of the SM. Moreover, they give information on key quantities for the calculation of the SM expectations in a yet unexplored domain, such as the parton densities of the proton or the photon. In addition to these experimental inputs, higher-order calculations are also needed to obtain precise expectations for SM processes, which are a key ingredient for the searches for new phenomena in high Q 2 and p 2 t processes at current and future experiments. The experimental and theoretical status of SM physics at high Q 2 and p 2 t is reviewed in the first part of this summary, with the remaining being dedicated to physics beyond the Standard Model. 1 Jet Physics at High p 2 t and Q 2 The production of jets at high-energy colliders is a very good testing ground of perturbative QCD, and a tool for determining the parton distribution functions of the proton and the photon. Possible deviation from the QCD predictions at the highest energy scales would be a hint for unrevealed new physics. A good understanding of exclusive multi-jet final states is also crucial in many searches for new-particle productions, such as the production and decay of R-parity-violating squarks. The status of jet production at HERA was reviewed in the photoproduc-tion 1 and DIS 2 regions. In photoproduction, dijet cross-sections have been measured up to p t,jet ≈ 80 GeV and m jj ≈ 150 GeV, and three-jet cross-sections up to m jjj ≈ 200 GeV. In the direct-photon regime the measurements are in good agreement with the NLO QCD predictions, while in the resolved-photon regime one finds a discrepancy, which could be attributed to the limited knowledge of the photon structure functions.