No abstract available

[en] The 'renormalon' or 'dispersive' method for estimating non-perturbative corrections to QCD observables is reviewed. The corrections are power-suppressed, i.e. of the form A/Q^p where Q is the hard process momentum scale. The renormalon method exploits the connection between divergences of the QCD perturbation series and low-momentum dynamics to predict the power, p. The further assumption of an approximately universal low-energy effective strong coupling leads to relationships between the coefficients A for different observables. Results on 1/Q² corrections to deep inelastic structure functions and 1/Q corrections to event shapes are presented and compared with experiment. Shape variables that could be free of 1/Q and α_s(Q²)/Q corrections are suggested

No abstract available

No abstract available

[en] Recent theoretical studies of jet fragmentation are reviewed, with emphasis on: i) soft gluon radiation patterns and the stringlike effect in perturbative QCD, ii) results on multiplicity moments, iii) heavy flavour fragmentation in a cluster hadronization model, and iv) properties of antipp Collider jets

[en] The aim of the lectures was to introduce techniques for performing simple calculations in quantum electrodynamics. Topics discussed in the lecture course included: the Klein-Gordon equation, Dirac equation and scattering amplitudes. (U.K.)

[en] A new Monte Carlo simulation scheme for jet evolution in perturbative QCD, which takes into account soft gluon interference, is combined with a no-parameter hadronization model based on the preconfinement and phase-space decay of colour-singlet clusters. Results of a preliminary comparison with data on e⁺e^- → hadrons are presented, and expectations for jets at hadron colliders are discussed

[en] Results of a new Monte Carlo simulation of initial-state gluon radiation in deep inelastic processes in the small-x region are presented. The simulation algorithm is based on the all-loops leading-logarithmic treatment of Catani, Fiorani and Marchesini. The results are compared and contrasted with those of a conventional branching algorithm based on the one-loop Altarelli-Parisi equations. For this study, the evolution of purely gluonic initial states in the region x>10^-5, Q²<10⁵ GeV² was investigated. The two approaches give similar results for the gluon structure function in this region, but differ on less inclusive properties of the emitted radiation. In particular, the multiplicity of emitted gluons is increased and large rapidity gaps are suppressed in the new treatment. This is due to the larger available phase space and to the new form factor corresponding to non-Sudakov virtual corrections. (orig.)

[en] The spin of the gluon gives rise to quantum correlations between azimuthal angles in QCD jet evolution, which are usually ignored or integrated out. Here they are computed and their effects are shown to be small. (orig.)

[en] Given the quark and gluon structure functions of the colliding hadrons at a single energy scale, quantum chromodynamics predicts the cross sections and angular distributions for the production of hadronic jets and lepton pairs at all large momentum transfers. The theory also makes predictions about the fragmentation of quark and gluon jets into hadrons. Recent developments in the comparison between theory and experiment are reviewed and some expectations for higher energies are presented. (author)