Jul 16 – 22, 2009
Kraków, Poland
Europe/Warsaw timezone

Selected recent HERMES results on parton distribution and fragmentation functions

Jul 17, 2009, 11:25 AM
Exhibition room B (Kraków, Poland)

Exhibition room B

Kraków, Poland

The Auditorium Maximum of the Jagiellonian University 33 Krupnicza Street 31-123 Kraków
QCD in hadronic physics VI. QCD in Hadronic Physics


Prof. Klaus Rith (University of Erlangen-Nürnberg and DESY)


The HERMES experiment at HERA has performed a new determination of the strange quark distribution s(x) from multiplicities of charged kaons in semi-inclusive deep-inelastic scattering (SIDIS) of 27.6 GeV electrons/positrons from deuterium. The extracted distribution function (DF) is much softer than that previously derived from dimuon events in neutrino/antineutrino scattering and those currently used in global PDF fits. Azimuthal asymmetries of identified hadrons in SIDIS from a transversely polarized hydrogen target and from unpolarized hydrogen and deuterium targets were measured. The former are caused by a convolution of the chiral-odd Collins fragmentation function (FF) and quark transversity (DF) or the convolution of the unpolarized FF and the naive time-reversal odd Sivers DF which can be related to orbital angular momenta of quarks in a polarized nucleon. The latter allow to access flavour dependent information about quark intrinsic transverse momenta and spin-orbit correlations. Examples are the Cahn effect, generated by the non-zero transverse motion of quarks and the Boer-Mulders effect, originating from a coupling between quark transverse momentum and transverse spin.

Primary author

Prof. Klaus Rith (University of Erlangen-Nürnberg and DESY)

Presentation materials