Renormalon phenomena in jets and hard processes

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/Qp 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 αs(Q2)/Q corrections are suggested