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WP2 Alignment Task: Status Report

This report examines the alignment monitoring and weak mode studies of the LHCb VELO vertex detector. It details methodologies for evaluating sensor alignment stability, misalignment variables including temperature and mechanical variations, and the effects of weak modes on alignment accuracy. The study utilizes data from the years 2010 and 2011 to analyze alignment precision. Furthermore, it discusses the relationship between alignment and various physics parameters, alongside an overview of the AIDA alignment web page for collaboration within the scientific community.

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WP2 Alignment Task: Status Report

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  1. WP2 Alignment Task: Status Report Introduction Alignment Monitoring – LHCb VELO Weak Modes – LHCb VELO AIDA Alignment Web page AIDA Telescope (WP9) Resolution – GEANT4 Material Description

  2. LHCb VELO • Highest precision vertex detector at LHC VELO Resolution vs pitch for 2 projected angle bin Moves for each LHC fill

  3. Monitoring With thanks to Giulio Dujany, CERN summer student

  4. Alignment monitoring • Variation of alignment, e.g. • Temperature effect • Mechanical variation • Monitoring in DQ offline procedure: • residual bias • Other physics parameters (PV, IP, etc.)

  5. Monitoring of sensor alignment • Residual along radial and azimuthal direction • Misalignment for x, y, z translation and rotation around x, y, z axis • Geometrical consideration to extract misalignment from the residual bias distribution Simplified formula

  6. Monitoring of Sensor Alignment • Misalignment evaluated: • Survey measurements • Alignment based on 2010 data • Alignment based on 2011 data RMS 0.86 ± 0.04 RMS 2.06 ± 0.09 Tx RZ Ty RMS 0.053 ± 0.003 RMS 0.130 ± 0.006 RMS 0.64 ± 0.03 RMS 2.44 ± 0.11

  7. Alignment stability on 2011 data • 2011 alignment • 3 period considered: June, July and August • VELO alignment stable in the considered period. • Method is used to monitor routinely the alignment stability

  8. Monitoring: 2 half alignment Fully open Closed pos. • VELO centred around the beam for each fill when the beam declared stable • Primary Vertex method: • Reconstruct PV using tracks in left or in the right side • Evaluation of misalignment by the distance between the two vertices X

  9. Monitoring: 2 half alignment 2010 data 2011 data • Stability of 2 half alignment by PV method: • within ± 5 m for Tx

  10. Weak Mode

  11. S. Ogilvy VELO: weak mode study • Weak mode: • Negligible effect on residuals and 2  Alignment procedure not sensitive to weak mode • Distortions on IP or other physics quantities • Main weak modes (strong dependence on detector geometry): • Twist around the z axis: R’z=Rz+ ·z • z- scaling • x or y shearing Mean IPy vs phi Collision Data MC weak mode

  12. S. Ogilvy VELO: weak mode study • Different constraints for different track samples • Collision data • Beam gas events • Sensitivity to some of this mode selecting the proper type of tracks

  13. Communication

  14. AIDA Alignment Web Page • Collect Alignment Contacts & Literature http://sborghi.home.cern.ch/sborghi/AIDAalignment/AIDAalignment/Home.html Will move to AIDA WP2 page

  15. AIDA Connections

  16. WP9 – MEDIPIX Telescope Daniel Hynds, Paula Collins et al. • Stunning performance Telescope • High track rate,1μm resolution,1ns timing • Huge testbeam programme of sensor testing performed this year • LHCb, ATLAS, RD50 sensors Will provide support software from WP2

  17. Plans and Summary Work towards AIDA Aims: Alignment Stability Monitoring Weak Modes Study Web Page • Dedicated PhD Student • Generalise Alignment work for AIDA • Forge links other expts • Apply software to pixel testbeam (WP9)

  18. Material Description Matt Reid et al. • Data / Simulation discrepancy at low PT • Material / multiple scattering • Dominant material component is 300μm Aluminium foil – very complex shape • Now studying tools CAD Drawings  GDML Thanks to John Apostolakis, Gabriele Cosmo

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