1. RPC Design Studies Gabriel Stoicea, NIPNE-HH, Bucharest CBM Software Week GSI-Darmstadt May 10, 2004

2. Outline Using CBM VMC for TOF simulations Geometry corrections TOF hits distribution and densities New TOF structure and shape? Summary

3. Using CBM VMC wrong rotation direction for TOF modules define each module with a symmetric RPC structure with 4 gaps: Al plate - 2mm gas gap - 0.3 mm glass - 1mm gas gap - 0.3 mm glass - 1mm printed circuit - composed from two copper foils and G10 (stesalit) in between - 1mm geometry corrections new material added to materials file - G10 (stesalit) Starting with TOFgeom.v03_v10.nml Using UrQMD like event generator (central Au+Au collisions at 25 AGeV), magnetic field on and STS & TRDs in front of TOF

4. Example trying to get hits distribution in xy plane: not corrected after correction 20 central events Au+Au at 25 AGev

5. TOF hits distribution Hits distribution in a xy plane at 10 m from the interaction point central Au + Au reactions at 25 AGeV (100 events) all charged particles

6. TOF hits densities Emission angle [mrad] area [m 2 ] N [hits/cm 2 /event] 50 0.53 0.79 x 10 -2 100 3.56 0.58 x 10 -2 200 14.64 0.23 x 10 -2 300 25.64 0.083 x 10 -2 400 39.19 0.037 x 10 -2 500 56.21 0.015 x 10 -2 Hit densities and detector areas for different emission angles. The hit density is calculated for central Au+Au at 25 AGeV. The areas are calculated assuming an elliptical shape which takes in account the deflection of charged particles in horizontal direction. Due to the large surface of the TOF (~140 m 2 ) it is unrealistic to buildTOF detector from single cell RPCs (complexity, price, dead zones). For outer regions not closed to the beam we can use strip readout RPCs. New geometry?

7. New TOF shape ? For ~9 m on horizontal direction and for a counter of about 1 m we have an angle of ~6.37 deg. and the total number of sectors is ~56 for full azimuthal covering. Outer wall poligonal structure built from strip readout RPCs. Inner wall - single cells. Overlap between modules in a given sector.

8. Summary real simulations -> event generator - magnetic field - all detectors in front of TOF, in CBM VMC environment function of distance & geometric efficiency -> size of the detectors + counting rate performance -> module size new TOF structure? - poligonal shape with an inner wall of single cell RPCs and an outer wall of strip readout RPCs starting to work at TOF Digitizer