QCD analysis of unpolarized and polarized Λ-baryon production in leading and next-to-leading order

We analyze experimental data for the production of Λ baryons in $e^{+}{e}^{-}$ annihilation in terms of scale-dependent, QCD-evolved, Λ fragmentation functions. Apart from the vast majority of the data for which the polarization of an observed Λ was not determined, we also consider the recent CERN LEP measurements of the longitudinal polarization of Λ’s produced on the $Z$ resonance. Such data correspond to spin-dependent fragmentation functions for the Λ. We point out that the present data are insufficient to satisfactorily fix these. We therefore suggest several different sets of fragmentation functions, all compatible with present data, and study the prospects for conceivable future semi-inclusive deep-inelastic scattering experiments to discriminate between them. We provide the complete next-to-leading order QCD framework for all the processes we consider.