Bonn 2020 – wissenschaftliches Programm
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HK 66.2: Hauptvortrag
Freitag, 3. April 2020, 15:00–15:30, H-HS X
The BGOOD experiment at ELSA - exotic structures in the light quark sector? — •Thomas Jude for the BGO-OD collaboration — Physikalisches Institut, Universität Bonn
The recent discoveries of the pentaquark, PC, states and XYZ mesons in the charmed quark sector began a new epoch in hadron physics, where multi-quark states beyond three and two quark systems have been realised. Such states could manifest as single colour bound objects, or evolve from meson-baryon and meson-meson interactions, creating molecular like systems and re-scattering effects near production thresholds. Intriguingly, similar effects may be evidenced in the light, uds sector in meson photoproduction. Access to a low momentum exchange and forward meson production region is crucial. BGOOD is uniquely designed to explore this kinematic region; a central calorimeter is complemented by a magnetic spectrometer in forward directions.
First results indicate a peak-like structure in the γ n → K0Σ0 cross section at W∼ 2 GeV consistent with the meson-baryon interaction model which predicted the charmed PC states. Unexpectedly, a drop in the γ p → K+Σ0 cross section at forward angles at W ∼ 1.9 GeV is also observed, consistent with threshold effects from meson-baryon interactions. BGOOD’s forward acceptance also enables identification of coherent photoproduction from deuterons. This is currently being exploited to study the dibaryon, d*(2380), which may have an important impact upon the equation of state for neutron stars.
Supported by DFG projects 388979758/405882627 and the EU’s Horizon 2020 programme, grant 824093.