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LHCb VErtex LOcator & Displaced Vertex Trigger

Chris Parkes, CERN. LHCb VErtex LOcator & Displaced Vertex Trigger. Vertex Detector  Design  Test Beam Results. . Displaced Vertex Trigger  Algorithm  Test Beam Emulation. . Conclusions  Summary  Future Plans. . Beauty ‘99. LHCb Detector. Chris Parkes. Beauty ‘99.

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LHCb VErtex LOcator & Displaced Vertex Trigger

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  1. Chris Parkes, CERN LHCb VErtex LOcator & Displaced Vertex Trigger Vertex Detector  Design  Test Beam Results  Displaced Vertex Trigger  Algorithm  Test Beam Emulation  Conclusions  Summary  Future Plans  Beauty ‘99

  2. LHCb Detector Chris Parkes Beauty ‘99

  3. Resolution Secondary Vertices  B tagging  Rejection of background  Primary vertex resolution 40 m  Chris Parkes Beauty ‘99

  4. Geometry series of discs Detectors separated 6cm during injection small overlap 10cm Chris Parkes Beauty ‘99

  5. Vertex Locator • Detector Length 1m • Station spacing varying from 4 - 12cm • Phi Overlap of detectors • Each Station has an R and a Phi measuring detector • Stereo angle between successive Phi Detector layers Chris Parkes Beauty ‘99

  6. Prototype Design r-detectors -measuring detectors 5 ° “stereo” tilt r-measuring detectors Both detectors utilize a double metal layer to readout inner strips whilst keeping electronics outside active area. -detectors Chris Parkes Beauty ‘99

  7. New Design 180 degree R & Phi Detectors  2048 strips  Smooth variation in pitch  16 chip Hybrid  Ready in Autumn  Chris Parkes Beauty ‘99

  8. Mechanics Chris Parkes Beauty ‘99

  9. Vacuum Vessel manipulators vessel Top Half window primary vacuum detectors 100cm RF shield vacuum barrier Chris Parkes Beauty ‘99

  10. Radiation Environment Including effects of walls, vessel High doses at tips  (1/r2) Detectors Irradiated  Test-Beam September n+ on n Silicon as base solution Dose after 1yr  1014 station 6  1 MeV equivalent neutrons/cm2   1013 1 2 3 4 5 6 cm Chris Parkes Beauty ‘99

  11. Modelling  Cooling Required  Electric Field Distortions  Radiation Response Chris Parkes Beauty ‘99

  12. Software LHCb will use C++ BUT Technical Proposal work was in FORTRAN  Test Beam used to gain experience with new language and Root All reconstruction software in C++ Cluster Making, Event Display, Track Fit, Alignment, Noise Studies...  Software Designed for future use both useful code, and class design  Chris Parkes Beauty ‘99

  13. Trigger Levels Chris Parkes Beauty ‘99

  14. Second Level Trigger Vertex Algorithm  IDEA  Separation of minimum bias events and B events by using the signature of displaced secondary vertices.  AIM  Minimum bias retention of less than 4% and a signal efficiency of more than 50%.  Boundary Conditions  Input event rate of 1 MHz or 2Gbytes/second .  Average execution time of about 250 microseconds.  Implementation  benchmark results show can be performed by 120 1000 MIP processors Chris Parkes Beauty ‘99

  15. Present Algorithm 2d   Track finding using triplets of r-clusters  track search starts in inner r sector  Primary vertex reconstruction, x y z, by crossing tracks of opposite phi-sectors  x y - resolution given by phi-sector  Selection of tracks with large impact parameter  Rejection of pile-up events r z Chris Parkes Beauty ‘99

  16. Algorithm cont. 3d   Add phi info. for large impact parameter tracks  ambiguities resolved by stereo angle  and impact parameter in xy-projection  find two track combinations which are close  calculate probability that one of the two tracks originate from the primary vertex  based on impact parameter  and geometry  calculate total L1 probability by multiplying the individual probabilities Chris Parkes Beauty ‘99

  17. Present Performance 2d and 3d track reconstruction efficiency of 98% and 95%. Primary vertex resolution of 80micron and 20micron for z and x/y. Chris Parkes Beauty ‘99

  18. Test Beam Spring ‘98 12 Silicon Planes Slow Electronics Chris Parkes Beauty ‘99

  19. Vertex Trigger Peformance Use Targets to simulate Primary Vertex  Resolution  Simulation 80 m  Test Beam Extrapolated 80 m  Assess sensitivity to detector misalignments  Chris Parkes Beauty ‘99

  20. Artificial B events ! Virtual B    Five events form one target  “minimum bias”  One From next target  B event Good Performance  Chris Parkes Beauty ‘99

  21. Overview of the readout scheme Analogue readout FE Rad. Hard >2Mrad/yr Front End Chip FADC + L1 DMILL- SCTA buffers 10m away or Processing in 0.25 m CMOS- BEETLE DSPs after L1 accept Chris Parkes Beauty ‘99

  22. LHC Speed Readout Chip Test-Beam Spring ‘99 Aim  Evaluate performance of detector equipped with SCT128A 40MHz FE chip Setup  6 plane Telescope + 2 Test Detectors Chris Parkes Beauty ‘99

  23. Test-Beam Results Clear Signal Observed Correlated with reference Telescope   Chris Parkes Beauty ‘99

  24. Time Response Rise Time ~ 25ns Pulse Remaining after 25ns ~ third of Signal 40% of LHCb events are preceded by an event simulation of B  Trigger efficiency drops above 30% overspill Signal:Noise ~ 20:1 Chris Parkes Beauty ‘99

  25. Conclusions Prototype Detectors Tested     New Design  Displaced Vertex Trigger     Future Work …..  So far the project is flying... Chris Parkes Beauty ‘99

  26. Milestones  2000 : Full Half station at 40MHz  2001 : Technical design Report  2003 : Construction  2004 : Commissioning  2005 : Start Data Taking But there is still a long way to cycle….. Chris Parkes Beauty ‘99

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