Soft-Gluon Resummation for the Fragmentation of Light and Heavy Quarks at Large x

We present a QCD study of fragmentation processes for light and heavy quarks in the semi-inclusive region of large x. Large logarithmic terms, due to soft-gluon radiation, are evaluated and resummed to all perturbative orders in the QCD coupling alpha_s. Complete analytical results to next-to-leading logarithmic accuracy are given for one-particle and two-particle inclusive distributions in e+e- annihilation and DIS. Factorization of parton radiation at low transverse momenta is exploited to identify the universal (process-independent) perturbative fragmentation function that controls heavy-quark processes, and to perform next-to-leading logarithmic resummation of its soft-gluon contributions. To gauge the quantitative impact of resummation, we perform numerical studies of light- and heavy-quark fragmentation in e+e- collisions.