1. A Barrel DIRC using radiator plates AntiProton ANnihilations at DArmstadt Study of QCD with Antiprotons Charmonium Spectroscopy Search for Exotics Hadrons in Medium Nucleon Structure Hypernuclear Physics … and more PANDA The PANDA Experiment at FAIR DIRC The DIRC Principle At the BaBar experiment at SLAC a DIRC was used for the first time and up to now for the only time. For the PANDA experiment the Barrel DIRC concept of BaBar is further developed. Plates A Geometry with Plates A new design concept for the DIRC involves wide plates instead of bars for the shape of the radiators. This plate-based barrel DIRC is currently under development and will be used within an upgrade of the Belle II experiment at KEK, Japan. Each plate has its own expansion volume consisting of fused silica prisms. DIRC with plates Reconstruction The reconstruction can be separated into two independent problems M. Zühlsdorf 1,2, K. Götzen 1, M. Patsyuk 1,2, K. Peters 1,2, C. Schwarz 1, J. Schwiening 1 1 GSI-Helmholtzzentrum für Schwerionenforschung, Darmstadt; 2 Goethe-Universität Frankfurt Work supported by EU6 grant, contract number 515873, DIRACsecondary-Beams, and EU FP7 grant, contract number 227431, HadronPhysics2, and the Helmholtz Graduate School for Hadron and Ion Research HGS-HIRe. Side view of the design looks quite familiar from BaBar reconstruction oMCP-PMTs give time and position in X and Y owith Y-position and plate position determination of θ C in Y-Z-plane In the top view a focusing would be very difficult if even possible Different approach ono assumptions concerning plate exit position have to be made oWith time of photon propagation and X on detector-plane one can count the number of reflections in X-Z-plane ofast timing (~100 ps) to fully reconstruct the photon path in X-Z-plane Resolution of reconstructed Cherenkov angle is influenced by several effects σ(θ C ) 2 tot =σ 2 Bar +σ 2 Pixel +σ 2 n(λ) +… σ 2 Bar → thickness of plate image; can be improved by focusing σ 2 Pixel → PMT pixel size σ 2 n(λ) → chromatic smearing; can be improved by fast timing (group velocity) Prototype Prototype Testing Prototypes of the plates and the fused silica prism are polished and will be tested in Summer 2012 at CERN. The new reconstruction will be applied for the first time. Prism Plates Target spectrometer DIRC detectors combine good PID performance and small radial expansion oother components are closer to the main vertex; therefore smaller and cheaper osmall energy loss when particles cross DIRC Detection of Internally Reflected Cherenkov light A charged particle with a high velocity crosses a transparent layer of a rectangular radiator bar which serves also as lightguide for the emitted cherenkov light. The light propagates to the edge of the radiator via total internal reflection. The radiator must have high optical qualities to provide good angle preservation and little photon loss during the light propagation. Specifications: Radiator: o80 rectangular bars osynthetic fused silica o17 mm x 35 mm x 2500 mm expansion volume with PMT plane oMCP-PMTs with 6.5 mm pixel size o30 cm from the bar end o~240 MCP-PMTs → ~15 000 pixels Fast timing and focusing optics improve the performance compared to the BaBar DIRC The reconstruction method for the Cherenkov angle depends on the design of the device. For the Bar Design the BaBar reconstruction approach is feasible. The necessary angle information is stored in lookup tables which are generated via Geant4 simulation. See the talk of M. Patsyuk (HK57.4 Fr. 12:00 P2). Particle Identification (PID) separate charged Pions and Kaons o0.5 – 4 GeV/c momentum range o5° – 140° angular range DIRC with bars It is clear that the photon hit patterns in the separated expansion volume will look quite different. In the displayed case one can see how the cherenkov ring pattern is folded in the separated expansion volume. With a more realistic geometry ring patterns are not recognizable. continuous EV separated EV Barrel DIRC Radiator Expansion Volume pi + going through radiator bar at 300 MeV/c (idealized geometry) λ[nm] n(λ) Dispersion-relation Prototype setup Contact: m.zuehlsdorf@gsi.de HK53.20 Pro: odesign proven to work (BaBar) Con: o~ 80 bars with highest optical quality → very expensive! Pro: o~16 plates (with lesser optical quality) → significant cost reduction! Con: owill new design work for PANDA? The reconstruction method of the bar design benefits from the small dimensions of the bar cross-section which is negligible compared to the size of the expansion volume (EV). As this is not valid for wide plates a new reconstruction method has to be developed and tested. The separated expansion volume makes a photon path reconstruction to some extend possible and is therefore an important piece of the new design.