The thrust and heavy-jet mass distributions in the two-jet region

Dressed Gluon Exponentiation (DGE) is used to calculate the thrust and the heavy-jet mass distributions in e(+)e(-) annihilation in the two-jet region. We perform a detailed analysis of power corrections, taking care of the effect of hadron masses on the measured observables. In DGE the Sudakov exponent is calculated in a renormalization-scale invariant way using renormalon resummation. Neglecting the correlation between the hemispheres in the two-jet region, we express the thrust and the heavy-jet mass distributions in terms of the single-jet mass distribution. This leads to a simple description of the hadronization corrections to both distributions in terms of a single shape function, whose general properties are deduced from renormalon ambiguities. Matching the resummed result with the available next-to-leading order calculation, we get a good description of the thrust distribution in a wide range, whereas the description of the heavy-jet mass distribution, which is more sensitive to the approximation of the phase space, is restricted to the range rho(H) < 1/6. This significantly limits the possibility to determine alpha(s) from this observable. However, fixing alpha(s) by the thrust analysis, we show that the power corrections for the two observables are in good agreement. (C) 2002 Elsevier Science B.V. All rights reserved.