Berlin 2005 – wissenschaftliches Programm

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HK: Physik der Hadronen und Kerne

HK 22: Postersitzung

HK 22.5: Poster

Montag, 7. März 2005, 16:30–18:00, TU MA141

Longitudinal single-spin asymmetries in semi-inclusive DIS — •Marc Schlegel and Andreas Metz — Institut fuer Theoretische Physik II, Ruhr-Universitaet Bochum, D-44780 Bochum, Germany

Non-zero single-spin asymmetries (SSA) in semi-inclusive lepton nucleon scattering have been observed recently by the HERMES collaboration. In general, SSA can be generated by time-reversal odd (T-odd) parton distributions and fragmentation functions, where the former are of particular interest, because they are non-zero only if the gauge-link in their operator definition is included [1,2]. The gauge link encodes the re-interaction of the struck quark with the target system. By means of a calculation in a perturbative spectator model for the nucleon we show explicitly that not only the leading twist SSA for a transversely polarized target is affected by the rescattering of the struck quark but also the twist-3 longitudinal SSAs (beam or target polarization) [3]. Our result indicates that previous analyses of these observables are incomplete. We also discuss if, for the twist-3 observables, the rescattering effect can be described by T-odd parton distributions in a factorized picture.

[1] Brodsky, Hwang, Schmidt [2] Collins [3] Metz, Schlegel