Abstract
A renaissance in hadron specroscopy in both meson and baryon sectors was triggered by the discovery of the enigmatic X, Y, Z states. Meanwhile, the discussion on unconventional quark-gluon compositions to understand their internal structure expanded to baryonic states in the charm sector, i.e. the pentaquark candidates observed at LHCb. Old problems and recent findings in the strange sector may suggest similar structures to exist there as well. In this light recent results and the ongoing new BGO-OD experiment at ELSA are discussed.
Highlights
During the 1990’s, high resolution meson photoproduction experiments like A2 at MAMI, CLAS at JLab, Crystal Barrel at ELSA or LEPS at SPring-8 set out to solve the socalled missing resonance problem of baryon spectroscopy
To analyse the extensive high quality date sets obtained, very sophisticated PWA and isobar models were developed, e.g. BnGa [1] or MAID [2], which were presented at this conference
Of particular interest is the energy-mass region around 2 GeV, the second and third resoance regions, where over 30 states expected in 3-quark potential models remained unseen in experiments
Summary
During the 1990’s, high resolution meson photoproduction experiments like A2 at MAMI, CLAS at JLab, Crystal Barrel at ELSA or LEPS at SPring-8 set out to solve the socalled missing resonance problem of baryon spectroscopy. It was hoped to observe baryon resonance states previously unseen in experiments using pion and kaon beams. Of particular interest is the energy-mass region around 2 GeV, the second and third resoance regions, where over 30 states expected in 3-quark potential models remained unseen in experiments.
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