Berlin 2005 – wissenschaftliches Programm
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HK: Physik der Hadronen und Kerne
HK 16: Elektromagnetische und Hadronische Proben
HK 16.6: Vortrag
Montag, 7. März 2005, 15:15–15:30, TU MA001
Omega production on the nucleon with linearly polarised photons at ELSA* — •Frank Klein — Physikalisches Institut, Universität Bonn
The reaction γ→ + N → ω + N was measured at the electron accelerator ELSA with the Crystal Barrel and TAPS calorimeter.
A 3.2 GeV electron beam from ELSA was used to obtain a tagged photon beam (0.6 - 2.6 GeV) by bremsstrahlung from a crystal radiator. Utilising the coherent bremsstrahlung at the aligned crystal radiator, we have produced linear polarised photons up to 2 GeV with a maximum degree of polarization of about 50 %. The photon beam impinged on a 5 cm long liquid hydrogen or deuterium target in the center of the Crystal Barrel detector. The 1290 CsI(Tl) crystals of the Crystal Barrel were complemented in this setup by 528 BaF2 crystals of the TAPS detector. The TAPS modules were arranged as a forward wall to cover the polar angles up to 30∘. The combination of these two detectors yields an azimuthally symmetric electromagnetic calorimeter, which covers 90% of 4π and is ideally suited for multi-photon final states and polarisation measurements. The measurement of polarisation observables in addition to the angular distribution of the omega production will help to disentangle the involved baryon resonances. This improves the identification of specific resonances. The neutral decay cascade of the omega: ω → π0 γ → 3 γ is used to reconstruct the produced ω. The status of the analysis of the photon beam asymmetry Σ and the unpolarized cross section will be reported.
* supported by DFG (SFB/TR 16).