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DT Barrel Alignment Using Standalone Muon Tracks

DT Barrel Alignment Using Standalone Muon Tracks. Luca Scodellaro Muon Barrel Workshop February 24 th , 2011. Outline. Brief remind of the methods MC analysis set up Reconstructing barrel geometry: ◊ Sectors ◊ Sector connection ◊ Wheels ◊ Whole barrel Final remarks.

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DT Barrel Alignment Using Standalone Muon Tracks

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  1. DT Barrel Alignment Using Standalone Muon Tracks Luca Scodellaro Muon Barrel Workshop February 24th, 2011

  2. Outline • Brief remind of the methods • MC analysis set up • Reconstructing barrel geometry: ◊ Sectors ◊ Sector connection ◊ Wheels ◊ Whole barrel • Final remarks

  3. Brief Remind of the Method

  4. Standalone Geometry with Tracks • Hardware alignment close to its design precision • Alignment with respect to the tracker might suffer for several effects: ◊ Tracker misalign., B field, material description • Exploring a third source of information: SA tracks • Millipede approach based on a linear approximation of residuals: R = B∆p + Aδ • B matrix hard to describe in a non-uniform magnetic field

  5. Standalone Geometry with Tracks • Trying an approach based on DT segments: ◊ Selecting tracks with pT>50 GeV/c ◊ For small movements, we can assume ∆p to depend only on chamber movements B ∆p = ACδinit = A’δfinal ◊ Simplified χ2 minimization

  6. MC Analysis Set Up

  7. Studies on MC • We want to understand the sensitivity we can reach on ideal MC • MC sample: ◊ CosmicMC_BON_10GeV_22X_V6_MuAlStandalone • Using 1Leg tracks used to improve pTmeasurements ◊ Same performances with 2Leg tracks and 2 iterations • The idea is to start from HW based alignment • A misalignment scenario has been generated by smearing ideal positions (local frame) by: ◊ Center of the chamber: 400 μm ◊ Orientation: 400 μrad

  8. Validation of the Fits • We reconstruct objects (sectors, wheel, etc.) in a standalone way • When comparing two geometries for an object, we look at the local coordinate of each chamber in a geometry in the reference system of the same chamber in the other geometry • The global transformation which minimize these coordinates is computed • Resulting local coordinates are presented

  9. Reconstructing Sectors

  10. Chamber to Chamber Fit • Residual distribution for YB0, Sector 10, Station 2 Misaligned geometry Corrected geometry (1 iter.)

  11. Chamber to Chamber Performance • Performance in chamber alignment vs. number of segments used

  12. Sector Recontruction Performance • Distance of chamber position from ideal geometry

  13. Sector Recontruction Performance • Performance in sector alignment vs number of segments in the chamber with lowest statistics

  14. Sector Connection

  15. Sector Connection Strategies • All chamber to chamber approach (All C2C): ◊ Treat all chamber separately ◊ Compute at the same time internal sector structure and sector relative position ◊ Alignment matrix A is 20x36 • Sector to sector approach (S2S): ◊ Froze sector structure ◊ Fit relative sector position by using segments from crossing tracks ◊ Alignment matrix A is 20x6

  16. Sector Connection Performance • Sector connection performance for All C2C and S2S:

  17. Sector Connection Performance • Sector connection performance with All C2C vs number of segments in the chamber with highest statistics

  18. Reconstructing Wheels

  19. Wheel Reconstruction • WheelS2S: using S2S strategy and fitting all sectors in a wheel together (A~172x258)

  20. Wheel Reconstruction • Details on the performance in local Y for subsets of sectors (all wheel was fitted)

  21. Wheel Reconstruction • Sector connection comparison for S2S and WheelS2S • WheelS2S connect the sectors as S2S (no degradation)

  22. Reconstructing Whole Barrel

  23. Barrel Reconstruction • Wheel2Wheel: same strategy as for WheelS2S but using frozen wheels instead of frozen sectors

  24. Final Remarks • Studies of standalone barrel alignment with MC cosmics basically complete • Testing on data ongoing: ◊Cosmics first: low statistics for certain barrel region, and ttrig not optimal ◊ Collisions data: better ttrig, better relative statistics between sector/wheel, no as much muon with high pT, no 1leg tracks ◊ Could use different datasets for each alignment step

  25. Backup Material

  26. Sector Recontruction Performance • Sector reconstruction with 1 leg tracks and 2 leg (2 iterations) tracks

  27. Chamber to Chamber Performance • Performance in the alignment of chambers between sectors

  28. Distribution of Segments in Cosmics Wheels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Sectors

  29. Sector Connection Performance • Sector connection performance for All C2C and S2S strategies

  30. Distribution of Segments in Cosmics Wheels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Sectors

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