Measurements of fragmentation functions and implications for semi-inclusive deep-inelastic scattering

Abstract

In this talk we will briefly review the present status of fragmentation function measurements with a focus on the more recent measurements of Collins-function related as well as of polarization-averaged single- and di-hadron fragmentation. We will further discuss limitations in the analysis of dihadron-fragmentation data arising through an incomplete integration of the differential cross section imposed by experimental constraints. In particular, we show that the usual application of momentum requirements together with integration over the polar angle of the hadrons in the di-hadron center-of-mass frame leads to a presently uncontrollable mix of various partial-wave components of the di-hadron fragmentation function, prohibiting precision extractions of di-hadron fragmentation functions from $e^+ e^-$ annihilation, semi-inclusive deep-inelastic scattering, or proton-proton collision data.