Non-perturbative effects in jet bremsstrahlung and the OPE

by Nikolai Uraltsev (CERN/PH-TH)

Friday 18 Nov 2005, 14:00 → 15:00 Europe/Zurich

TH Auditorium (CERN)

The operator product expansion, where applicable, provides a model-independent description of the soft non-perturbative effects in short-distance processes. The gluon radiation off the ultra-relativistic coloured particles exhibits, however, a peculiarity absent from the Euclidean processes: emission of a highly collinear gluon can be driven by the running strong coupling at arbitrarily low scale, regardless of the gluon energy. Since the standard local OPE assumes limited wave vectors and frequencies for the soft modes, this may potentially bring in non-perturbative effects not captured by the standard local OPE. Nevertheless, it is shown that the principal non-perturbative OPE relations, for instance, in inclusive heavy flavour decays, are not modified by gluon bremsstrahlung. In particular, the integer moments of the inclusive hadron mass square distributions are non-perturbatively affected only by the soft radiation, while high-energy collinear gluons contribute only in the small-coupling regime.