Erlangen 2026 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 8: Instrumentation I

HK 8.7: Talk

Monday, March 16, 2026, 18:00–18:15, PHIL A 301

Mirror System and Mirror Alignment Monitoring of the CBM RICH — •Sven Peter for the CBM collaboration — Justus Liebig University, Gießen

The CBM (Compressed Baryonic Matter) experiment at FAIR (Facility for Antiproton and Ion Research) will study extremely dense matter resulting from heavy ion collisions starting in 2028. The CBM Ring Imaging Cherenkov Detector (RICH) uses CO₂ as radiator and multi-anode photomultiplier tubes as readout. The mirrors (R=3 m) consist of 80 individual mirror tiles (about 40 cm×40 cm). A prototype of the mirror wall has been built and a gluing procedure has been developed that does not cause harmful distortion of the mirror. The RICH is planned to be periodically exchanged with the MUCH (Muon Chamber) detector by craning. This carries the risk of mirror misalignment but only misalignment upto 1 mrad can be tolerated. Potential misalignment must be detected and accounted for during data analysis to ensure accurate ring diameters, locations, and subsequent ring-track matching. The CLAM method (Continuous Line Alignment and Monitoring, originally developed for the COMPASS RICH-1) was adapted for the CBM RICH. A ray-optics simulation of the mirror system was used to compare different approaches for misalignment quantification. Supported by BMBF grant no. 05P24RG6.

Keywords: CBM; FAIR; RICH; Mirror Alignment; Detector