Köln 2004 – scientific programme

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HK: Physik der Hadronen und Kerne

HK 27: Electromagnetic and Hadronic Probes IV

HK 27.4: Talk

Wednesday, March 10, 2004, 11:45–12:00, E

Omega photoproduction off solid targets — •David Trnka — II. Physikalisches Institut, Heinrich-Buff-Ring 16, 35392 Giessen

Omega photoproduction off solid targets is a powerfull tool to investigate possible in-medium modifications of hadronic properties. A variety of theoretical models predict a shift of the omega meson mass in the order of −140 MeV <m^*−m_V < −15MeV and a broadening of the width within a range of 20 to 50 MeV at normal nuclear densities (i.e. :[1]). From March to May 2003 data off C, Ca, Nb and Pb has been obtained at the ELSA accelerator facility in Bonn using the combined detector system of Crystal Barrel and TAPS, providing an almost 4π coverage for photon (and also charged particle) detection. The incident electron beam energy was chosen to be 2.8 GeV. The photon beam is produced via the Bremsstrahlung process off a thin radiator, covering a tagged range of 31 to 94 % of the incident beam energy. The Reaction γ + A → ω + X is identified via the decay mode ω → π⁰+γ → γγγ by detecting the three photons. Simulations ([2]) prove the feasibility of measuring in-medium modifications and show that distortions due to FSI of the pions can be eliminated. First indications of an ω mass shift have been observed and the dependence on the ω-momentum has been studied. These prelimary results will be compared to recently published calculations, which take the experimental resolution into account ([3]).

[1] T. Renk et al. , Phys. Rev. C 66, (2002) 014902

[2] J. G. Messchendorp et al. , Eur. Phys. J. A. 11, 95-103 (2001)

[3] P. Mühlich et al., arXiv:nucl-th/0310067