M. Becker

THE BGO-OD EXPERIMENT AT ELSA

Meson photoproduction is a key tool for the experimental investigation of the nucleon excitation spectrum. To disentangle the specific couplings of resonances, in addition to the rather well measured pion and eta photoproduction channels it is mandatory to obtain information on channels involving strange and vector mesons and higher mass pseudoscalar mesons, and the associated multi-particle final states with both charged and neutral particles. In this respect, the new BGO-OD experiment at the ELSA accelerator of the University of Bonns Physikalisches Institut provides unique instrumentation. We describe the experiment, present its status and the initial program of measurements.

Strangeness Photoproduction at the BGO-OD Experiment

The BGO-OD experiment at the ELSA accelerator facility uses an energy tagged bremsstrahlung photon beam to investigate the excitation structure of the nucleon. The setup consists of a highly segmented BGO calorimeter surrounding the target, with a particle tracking magnetic spectrometer at forward angles. nBGO-OD is ideal for investigating low momentum transfer processes due to the acceptance and high momentum resolution at forward angles. In particular, this enables the investigation of strangeness photoproduction where t-channel exchange mechanisms play an important role. This also allows access to low momentum exchange kinematics where extended, molecular structure may manifest in reaction mechanisms. nFirst key results at low

Determination of the real part of the

t

\eta

indicate a cusp-like structure in

'-Nb optical potential

K^+Sigma^0

Determination of the real part of theη′-Nb optical potential

photoproduction at

Determination of the real part of the η′-Nb optical potential

W = 1900

The BGO calorimeter of BGO-OD experiment

,MeV, line shapes and differential cross sections for

Recent Results of the BGO-OD Experiment at ELSA Facility

K^+Lambda

The {\eta}'-carbon potential at low meson momenta

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