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Particles and Fields

Eur. Phys. J. C 22, 269-276 (2001)
DOI: 10.1007/s100520100815

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

S. Kretzer1, E. Leader2 and E. Christova3

1  Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48823, USA
2  High Energy Physics Group, Imperial College, London, UK
3  Institute of Nuclear Research and Nuclear Energy, Sofia, Bulgaria

(Received: 6 August 2001 / Revised version: 3 October 2001 / Published online: 12 November 2001 - © Springer-Verlag / Società Italiana di Fisica 2001 )

By combining recent HERMES data on semi-inclusive DIS (SIDIS) $\pi^\pm$-production with the singlet fragmentation function $D_\Sigma^{\pi^+}$, which is well determined from e+e- data, we are able to extract, for the first time, the flavoured fragmentation functions $D_u^{\pi^+}$, $D_d^{\pi^+}$ and $D_s^{\pi^+}$ without making any assumptions about favoured and unfavoured transitions. Whereas $D_u^{\pi^+}$ and $D_d^{\pi^+}$ are very well determined, the accuracy of $D_s^{\pi^+}$ is limited by the uncertainty in evolving $D_\Sigma^{\pi^+}$ from the Z0 pole down to the SIDIS scale of a few (GeV)2. We discuss how the precision on $D_s^{\pi^+}$ could be improved. Knowledge of the $D_{q=u,d,s}^{\pi^+}$ 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.

© Società Italiana di Fisica, Springer-Verlag 2001