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MVD Simulations with Digitizer

MVD Simulations with Digitizer. Christian Trageser 1 , Michael Deveaux 1,3 , Christina Dritsa 1,2,3 IKF Frankfurt 1 , GSI Darmstadt 2 , IPHC Strasbourg 3. CBM Collab. Split Croatia, Oct 05- 09.10.2009. Outline Motivation Simulation Setup Results Summary and Conclusion.

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MVD Simulations with Digitizer

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  1. MVD Simulations with Digitizer Christian Trageser1, Michael Deveaux1,3, Christina Dritsa1,2,3 IKF Frankfurt1, GSI Darmstadt2, IPHC Strasbourg3 CBM Collab. Split Croatia, Oct 05- 09.10.2009 • Outline • Motivation • Simulation Setup • Results • Summary and Conclusion

  2. Motivation: Running conditions of the MVD Mean hit density from nuclear collisions (@ 10cm) Incl. delta electrons from the target ~700 hits / evt Hits/mm²/coll. x 1000 Rate Hits (Max.) 100 kHz => 0.7k (1/mm²) 1 MHz => 7k (10/mm²) 10 MHz => 70k (100/mm²) Adapt beam to abilities of the detector! Hot spots up to 1 hit / evt / mm2 Even more difficult for first station at 5 cm

  3. Motivation Efficient STS – MVD Track matching is essential for good open charm reconstruction! Can the MVD, STS and L1-Tracking provide a sufficient tracking efficiency? • Approach: • Use the newly available MVD-Digitizer • Study tracking quality including delta-electrons and pile-up • Benchmark different geometries according to: • Tracking efficiency • p-resolution • Impact parameter resolution • Number of tracks passing the single track selection cuts

  4. Simulation Setup • Global simulation setup: • CbmRoot JUN 09 • MVD (with Digitizer), STS (with Digitizer), other detectors absent • Simulated geometries: • STS => Standard geometry JUN 09 • MVD => Two options simulated: • 2 Stations (z= 10, 20 cm; Thick: 500 µm) • Inner radius: 5.5 mm (z=10 cm), 10.5 mm (z=20 cm) • 3 Stations (z= 5,10,15cm; Thick: 300, 500, 600 µm • Inner radius: 5.5 mm (z=5,10 cm), 10.5 mm (z=15 cm) • Collision system: • Au-Au @25 AGeV

  5. Simulation Setup MVD-Digitizer Settings: Pixel pitch = 18.4 µm ADC = 12 bit Threshold = 1 Electron Noise = 15 Electrons Fake hit generator = Off Ideal readout Pixels with signal charge receive noise BUT: No fake hits are created due to noise Cuts: Long tracks  More than 7 hits in MVD + STS p > 1 GeV

  6. Cluster merging as function of pile-up Up to 20% of all clusters are merged > 80% of all merged clusters are in the delta electron region

  7. Momentum resolution (only “long” tracks) preliminary Momentum resolution gets moderately worse for higher pile up The results indicate no difference between the two geometries

  8. MVD Tracking Efficiency Only long tracks. Only tracks in acceptance. Assume tracking successful if no wrong hit or merged cluster is associated in the MVD Factor 5 in inefficiency preliminary MVD Tracking Efficiency decreases for high pile up The results indicate no difference between the two geometries

  9. IP Resolution as function of pile-up 2 Stations prelimínary Response for “bad tracks” not Gaussian => RMS shown 50 Good tracks: IP Resolution < 80 µm (RMS) „Bad“ tracks: IP Resolution ~ 600 µm (RMS), would be better without MVD

  10. IP Resolution (RMS) for all and only good tracks Good tracks All tracks preliminary preliminary Mind the scale! IP-resolution of all tracks gets worse with increasing pile-up The Comparison of the two geometries show no clear trend (yet)

  11. Efficiency drop of the PV-cut Fraction of tracks passing the PV-cut (Only primary BG tracks are included, reject Strange particles) preliminary x 4 Number of accepted background tracks increases by a factor four Mostly, “bad” tracks are accepted

  12. Summary and conclusion • The impact of pile-up on the MVD-tracking was studied • We observe: • Few impact on momentum resolution • A substantial impact on tracking efficiency: • 97 % => 87 % (> 1GeV “long” tracks) • A decreased eff. of the PVChi-cut: • 97% rejection => 88% rejection (> 1GeV “long” tracks) • Our results show few preferences for a specific detector design (yet) • Conclusion: • Shrinking MVD tracking efficiency is an issue. • Substantial room for optimization, needs interaction with tracking experts • Next steps: • Repeat study with higher statistics • Study detector layouts in a systematic way • Estimate SvZ-Resolution • Start a study on open charm reconstruction • Optimize hit finding

  13. Thank you for your attention!

  14. Cluster merging as function of pile-up > 80% of all merged clusters are in the delta electron region

  15. Digitizer: Simulated vs. measured resolution 18.4 µm pitch 1 bit readout Threshold = threshold N

  16. IP Resolution as a function of Pile-up 3 Stations preliminary Same trend for

  17. Running conditions of the MVD Hits/event distance between station and target[cm] The occupancy is dominated by delta electrons generated in the target. Handling them needs detector with very high granularity

  18. Motivation Good track finding is essential for open charm reconstruction. • To find a optimized Geometry for the MVD • Check Tracking Efficiency • Check Efficiency of the cuts • Different pile up scenarios

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