1. 9th October 2003Danny Hindson, Oxford University1 Inner Detector Silicon Alignment Simple approach -Align in stages + rely on iteration Barrel to Barrel alignment -All 6 degrees of freedom -Update on convergence problems Internal Barrel alignment -Full detector demo of rphi and z alignment

2. 9th October 2003Danny Hindson, Oxford University2 Barrel to Barrel Alignment Plot phi residual and z residual surfaces Fit known functions for each of 6 dof Eg X Translation gives sine wave on phi residual surface

3. 9th October 2003Danny Hindson, Oxford University3 Extract misalignments from surface Fit these functions to the surfaces: -  res = A+ Bsin  - Ccos  + Dzcos  - Ezsin  - Z res = F+ Drsin  - Ercos  Issues -phi movements of SCT modules creating an effect on the z residual surface (even for  =0 tracks) Possibly caused by iPatRec tolerances affecting rphi and rphi’ differently Currently derive D and E (X and Y rotations) from phi surface only –Will retry with iPatRec v6.5.0 very shortly Eg A=rotation about z axis B=X translation

4. 9th October 2003Danny Hindson, Oxford University4 Barrel to Barrel Results Randomly shuffle 6 dof of the seven barrels -Rotations, RMS=0.2 mrad -Translations, RMS=100 μm Converges on sagitta distortion Previously had problems with convergence –Especially x and y rotations –Tried various things Multiple scattering? Tried higher energy tracks => no change Tried limiting tracks to eta<1. Some tracks were hitting endcaps -Situation much improved (now ~20 iterations rather than 50+)

5. 9th October 2003Danny Hindson, Oxford University5 Sagitta Distortions Sagitta type distortion for each of the 6 dof (tested down to 6 GeV) Final barrel positions are a combination of all 6 Rotations about z axisX/Y translations Y rotation~ X translation (z)

6. 9th October 2003Danny Hindson, Oxford University6 Convergence problems

7. 9th October 2003Danny Hindson, Oxford University7 How do I tell if it’s worked? Sagitta distortions are complicated: –To visualise –To undo Use E/p (need lot of tracks) In some cases I can’t fully do this Plot p t and impact parameter resolution –Plot a 2D profile histogram of p t vs eta –Take width of each bin and plot on simple histogram Do this before and after 1/p t resolution at 40 GeV is ~1 TeV -1 for perfect detector

8. 9th October 2003Danny Hindson, Oxford University8 Internal Barrel Alignment Adopted simple approach -Align rphi and z within rings -Align rings relative to each other Use overlaps to determine relative positions –More tolerant than basic residual to misalignments in other barrels Lot of issues highlighted last time – some progress

9. 9th October 2003Danny Hindson, Oxford University9 Internal Barrel Alignment 1) Pixel z overlaps quite small -Can`t ignore edge channels, since these are 300  m long (lose 75-90% of overlap hits) -Have measured bias introduced by keeping them (30-75μm) 2) Full ring rotations mimic change in radius -Each overlap gives a non-zero reading -Because overlap residual is a function of (actual incidence angle)-(fitted incidence angle) 3) iPatRec alignment tolerances -Now have v6.5.0. -Not sure if faster convergence compensates for slower speed

10. 9th October 2003Danny Hindson, Oxford University10 Internal Alignment Demonstration Shuffle all modules in all 7 barrels in rphi –3530 modules in TDR geometry –RMS of shuffle 0.1 to 0.2 mrad 2.5 million 6 GeV muon tracks spread over eta<1.5 Used v3.0.2 of iPatRec

11. 9th October 2003Danny Hindson, Oxford University11 Results RMS before (mrad)RMS after (mrad) Barrel 0 0.2 (=8 microns)0.126 1 0.20.055 2 0.20.096 3 0.10.046 4 0.10.036 5 0.10.032 6 0.075 (=39 microns)0.041 Tracks don’t hit all rings Converged after 6 iterations (pattern recognition => ~24 hours)

12. 9th October 2003Danny Hindson, Oxford University12 Example of one ring – Pixel barrel 1

13. 9th October 2003Danny Hindson, Oxford University13 Future Visualisation tool –Possible to improve 3D behaviour? (ROOT?) Aims –Run full demo combining full barrel misalignments with internal rphi/z misalignments –If time: Look at rotations around local z axis Better approach to z overlaps in pixel detector