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T: Teilchenphysik

T 606: QCD II

T 606.3: Talk

Tuesday, March 8, 2005, 17:00–17:15, TU H2035

Measurement of exclusive pion production at HERMES — •Ivana Hristova — DESY, 15738 Zeuthen

In the framework of Generalised Parton Distributions (GPDs), a large single-spin azimuthal asymmetry (SSAA) has been calculated for exclusive production of π⁺ mesons from a transversely polarised target by longitudinal virtual photons.

The HERMES experiment at DESY has observed a non-zero SSAA using a longitudinally polarised gas target although the transverse component of the target polarisation relative to the virtual photon was small. Encouraged by these and other results, a new target magnet was installed and data with transversely polarised hydrogen were taken since 2002.

We will review the results obtained from the longitudinally polarised target and report on the progress of analysis of data from the transversely polarised target. The latter will yield the transverse asymmetry directly and thus allow access to GPDs.