INFRARED RENORMALONS AND POWER SUPPRESSED EFFECTS IN E(+)E(-) JET EVENTS

We study the effect of infrared renormalons upon shape variables that are commonly used to determine the strong coupling constant in e(+)e(-) annihilation into hadronic jets. We consider the model of QCD in the limit of large n(f). We find a wide variety of different behaviours of shape variables with respect to power suppressed effects induced by infrared renormalons. In particular, we find that oblateness is affected by 1/Q non-perturbative effects even away from the two-jet region, and the energy-energy correlation is affected by 1/Q non-perturbative effects for all values of the angle. On the contrary, variables like thrust, the c parameter, the heavy jet mass, and others, do not develop any 1/Q correction away from the two-jet region at the leading n(f) level. We argue that 1/Q corrections will eventually arise at subleading n(f) level, but that they could maintain an extra alpha(s)(Q) suppression. We conjecture therefore that the leading power correction to shape variables will have in general the form alpha(s)(n)(Q)/Q, and it may therefore be possible to classify shape variables according to the value of n.