Phenomenology of Power Corrections in Fragmentation Processes in e+e− Annihilation

We analyse power corrections to longitudinal and transverse fragmentation processes in ee annihilation, based on the assumption of ultraviolet dominance of power corrections. Under this assumption, we determine the dependence of power corrections on the scaling variable x from the infrared renormalon asymptotics of leading power coefficient functions. Our results suggest that the longitudinal and transverse gluon fragmentation coefficient functions receive corrections of order 1/(xQ). The power expansion breaks down at x < Λ/Q and has to be resummed. This resummation leads to 1/Q corrections to the longitudinal and transverse cross section, which cancel for the total cross section. We provide a simple parametrization of the x dependence of 1/Q corrections to fragmentation processes and investigate perturbative corrections to the longitudinal cross section in higher orders, in view of a determination of the strong coupling. ∗On leave of absence from Università di Torino, Torino, Italy.