paper

Fragmentation functions from semi-inclusive DIS pion production and implications for the polarized parton densities

arXiv:hep-ph/0108055 · doi:10.1007/s100520100815

Abstract

By combining recent HERMES data on semi-inclusive DIS $I ¨ ^{\pm}$ -production with the singlet fragmentation function $D_{I^} £^{I ¨ ^{+}}$ , which is well determined from $e^{+} e^{-}$ data, we are able to extract, for the first time, the flavoured fragmentation functions $D_{u}^{I ¨ ^{+}}$ , $D_{d}^{I ¨ ^{+}}$ and $D_{s}^{I ¨ ^{+}}$ without making any assumptions about favoured and unfavoured transitions. Whereas $D_{u}^{I ¨ ^{+}}$ and $D_{d}^{I ¨ ^{+}}$ are very well determined, the accuracy of $D_{s}^{I ¨ ^{+}}$ is limited by the uncertainty in evolving $D_{I^} £^{I ¨ ^{+}}$ from the $Z^{0}$ pole down to the SIDIS scale of a few $(G e V)^{2}$ . We discuss how the precision on $D_{s}^{I ¨ ^{+}}$ could be improved. Knowledge of the $D_{q = u, d, s}^{I ¨ ^{+}}$ will permit the extraction of the polarized parton densities from future polarized SIDIS asymmetry measurements. We study the precision that can be expected in such an extraction.

19 pages, 7 figures, minor changes for publication in EPJC