No Arabic abstract
Jet production in electron-proton collisions at HERA provides a unique testing ground for Quantum Chromodynamics (QCD). Apart from the determination of the strong coupling constant $alpha_s$, ep jet data may especially be used to gain insight into the dynamics of the exchanged parton cascade, whose structure is probed by the high-$E_T$ dijet system; thus information on the parton content of the proton and (quasi-)-real and virtual photons is obtained. This report touches some of these aspects revealed in recent jet data from the HERA experiments which are testing perturbative QCD at the limits of applicability.
In this short report, we discuss the Jet Physics results and perspectives at HERA, Tevatron and LHC.
Recent results from the HERMES experiment at HERA are described. The large data set from Run-I has yielded new information on the helicity structure of the nucleon. The data to be taken in Run-II will deal mainly with the transverse spin structure and with exclusive reactions.
The high energy programme of the HERA collider ended in March 2007. During the whole HERA programme, a combined total integrated luminosity of 1 fb$^{-1}$ was collected by the H1 and ZEUS experiments. In this context, an overview of the most recent results of both experiments concerning searches for new physics is presented. The topics covered are searches for contact interactions, leptoquarks and excited leptons, as well as studies of the isolated lepton and multi-lepton topologies, and a general signature based search.
Recent results on the searches for new physics in ep collisions at HERA using the ZEUS and H1 detectors are presented. No evidence for excited fermions or supersymmetric particles within the context of the Minimal Supersymmetric Standard Model nor R-parity violation has been found using an integrated luminosity of up to 20 inv pb. New limits have therefore been established.
We compute various kinematical distributions for one-jet and two-jet inclusive photoproduction at HERA. Our results are accurate to next-to-leading order in QCD. We use the subtraction method for the cancellation of infrared singularities. We perform a thorough study of the reliability of QCD predictions; in particular, we consider the scale dependence of our results and discuss the cases when the perturbative expansion might break down. We also deal with the problem of the experimental definition of the pointlike and hadronic components of the incident photon, and briefly discuss the sensitivity of QCD predictions upon the input parameters of the calculation, like $alpha_S$ and the parton densities.