Suppressed power-corrections for moments of event-shape variables in e+e- annihilation
Abstract
Power-corrections that fall as 1/Q, where Q is the center-of-mass energy, play a significant role in the phenomenology of the average values of event-shape variables like the thrust T. These power-corrections can be analyzed in perturbative QCD using renormalon resummation in the single dressed gluon approximation. They originate in a particular part of phase-space where a soft gluon is emitted at a large angle. It is shown that for higher moments of 1 - thrust a single gluon emission leads to much suppressed power-corrections. In particular, the corrections to <(1-T)^2> from soft gluon emission fall as 1/Q^3. Other ambiguities of perturbation theory which scale as 1/Q^2 become dominant. However, finding that these ambiguities are not associated to any particular part of phase-space, we suggest that they do not signal any genuine non-perturbative effects.Keywords
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