Münster 2011 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 4: Hadronenstruktur und -spektroskopie I

HK 4.7: Vortrag

Montag, 21. März 2011, 15:45–16:00, C-2

Measurement of the beam-target double polarisation observable, E for γ(p,K⁰)Σ⁺ with the CBELSA/TAPS experiment at ELSA — •Thomas Jude — Physikalisches Institut, Universität Bonn

The measurement of single and double polarisation observables is crucial for the determination of baryon resonance structure. There is a global effort to provide sufficient observables for model independent determination of contributing amplitudes for meson photoproduction channels. Recent measurements of the beam-recoil observables C_X and C_Z for γ(p,K⁺)Λ support a simple model where the strange constituent quark retains the full polarisation of the incident photon. The extraction of the polarisation observable, E for γ(p,K⁰)Σ⁺ will provide further constraints to this model, and help to determine t-channel contributions for this channel.

Data were taken with the Crystal Barrel and MiniTAPS detectors combined as the CBELSA/TAPS experiment at the electron stretcher facility, ELSA. The Crystal Barrel consists of 1380 CsI(Tl) crystals, covering a polar angle of 12-160^∘. MiniTAPS is an array of 218 BaF₂ crystals covering forward angles. Circularly polarised, energy tagged bremsstrahlung photons were incident upon a longitudinally polarised butanol target. The γ(p,K⁰)Σ⁺ channel was analysed using a kinematic fit from the decays: K⁰ → π⁰π⁰ and Σ⁺ → p π⁰. Presented are preliminary measurements and interpretations.

Supported by the DFG (SFB/TR-16)