1. Muon Barrel Geometry Studies Luca Scodellaro Muon Barrel Workshop July 6 th, 2010

2. Outline Studies of the latest hardware-based barrel geometry Studies for a standalone barrel geometry with tracks Inclusion of quality control measurements

3. Studies of Latest HW Geometry Latest barrel geometry sign-off at the PVT meeting on May 12 th and used for ICHEP Use DT segments to study relative alignment of neighbour chambers in the same sector Use new track collection with t0 correction from May 24 th reprocessing > bottom-top asymmetry Look for systematic effects

4. Bottom-Top Asymmetry Comparison of residual distributions Top Bottom Old collection New collection

5. Performance of HW Geometry Means of ∆X distributions

6. Performance of HW Geometry Means of ∆dX/dY distributions

7. Performance of HW Geometry Means of ∆Y distributions

8. Performance of HW Geometry Means of ∆dY/dZ distributions

9. Bottom-Top Comparison (mrad) Mean distributions for hemisphere Bottom sectors Top sectors

10. Comparison by Station (mrad) Mean distributions for station Station 1 to 2 Station 2 to 3 Station 3 to 4

11. Wheel to Wheel Twist Select tracks crossing two wheels Use DT segments connecting neighbour chambers: (final station-initial station)= ± 1 (final wheel-initial wheel)= ± 1 Assumeing YB0 as a reference and extrapolating DT segments towards external wheels: no significant twist of wheels observed

12. Wheel to Wheel Twist Global results W-2 vs W-1W-1 vs W0 W1 vs W0W2 vs W1

13. Wheel to Wheel Twist Station by station results Station 1 to station 2 Station 2 to station 3 Station 3 to station 4

14. Standalone Geometry with Tracks Hardware alignment close to its design precision Alignment with respect to the tracker might suffer for several effects > track misalignment, B field, material description We want to improve our standalone description of the barrel using tracks Millepede approach based on a linear approximation of residuals: R = B∆p + A δ B matrix hard to describe in a non-uniform magnetic field

15. Trying an approach based on DT segment > for small movements, we can assume ∆p to depend only on chamber movements B ∆p = AC δ init = Aδ final > simplified χ 2 minimization Using half statistic to fit chamber movements inside a sector, the other half to test the new geometry with the usual method (tighter cuts) Standalone Geometry with Tracks

16. Residual Distributions YB0, Sector 11, Station 2 (mrad) Corrected distribution Uncorrected distribution

17. Mean Distributions (mrad) Corrected geometry Uncorrected geometry

19. Quality Control Measurement Correction distribution

20. Segment Validation (mrad)

21. Conclusions We studies the performances of the latest hardware-based barrel geometry > still some top-bottom asymmetry observed > no major systematic so far identified with segments Quality control measurement added to internal chamber description Starting to develop a standalone track-based geometry