1. 1 Status of Tracker Alignment b-tagging Workshop 29.10.08 Nhan Tran (JHU) On behalf of the Tracker Alignment Group

2. 2 Outline Misalignment and b-tagging Standard CSA07/08 scenarios Effect of APE Overview of recent experience with Global Runs CRUZET results and first CRAFT data Towards APE and resolution Outlook

3. 3 Introduction: Misalignment and b-tagging Track and vertex reconstruction (and thus b-tagging) is highly affected by misalignment Standard CSA07/08 misalignment scenarios SurveyLASOnly; SurveyLASCosmics (Startup); 10 pb -1 ; 100 pb -1 PXB Alignment vital Alignment Position Errors (APE) - added to track errors to maintain track finding efficiency Affects track impact parameter significances For further studies, please refer to CMS NOTE 2008/029 & CMS AN 2007/047

4. 4 CRUZET (B = 0T) Alignment with nearly whole tracker - good turnaround of alignment constants Two samples of selected tracks July, 285k tracks August, 345k tracks No magnetic field, no momentum measurement Running both HIP and MillePede algorithms - similar results First experience with pixel detector - half barrel alignment Improvement of track  2 and hit residuals pixel hit strip hit Distribution dependent on momentum assumption

5. 5 CRUZET Results Effect of alignment on tracking: Idea to split cosmics tracks along impact parameter and compare track parameters of top and bottom halves Alignment shows improvement in bias and resolution of the track parameters  d xy and  (also for  d z and  ) Cosmic splitting n.b. No pixels…Stay tuned to CRAFT!

6. 6 First CRAFT Data (B = 3.8T) Expect ~ 3 weeks of CRAFT running After a “bumpy” start, results improving - data still coming in! As of 10h CET, ~ 1.3 M events Still many things to understand Tracking variable distributions Pixel hit efficiency p T distributions Cut optimization Expecting pixel statistics for module level alignment Observing 0.7% of tracks with at least one pixel hit First attempt at ladder level Pixel APEs under investigation PXF appear underestimated

7. 7 Towards Resolution and APE Unique  -dependent systematics for cosmics Methods dependent on Cosmic MC (in production) - no definitive results yet Distribution of the mean of the residuals, residuals from high-pT tracks, MC-tuning of residuals, APE-tuning Preliminary results show better-than-expected resolution for strip barrel modules with good statistics Focused alignment group efforts underway Distribution of the mean of residuals in CRUZET; Modules with > 100 modules preliminary Waiting for corresponding MC…

8. 8 Outlook First experiences with Global Runs positive from tracker alignment perspective - still many things to understand PXB alignment and APE estimation vital for b-tagging Expect statistics for alignemnt of PXB at module level APE estimation under investigation - high priority Standard CSA07/08 Scenarios affected Unforeseen PXB alignment - unknown level of achievable alignment at this time Strip Tracker resolution overestimated for modules with good statistics Pixels still under investigation in CRAFT - PXF appear underestimated; PXB case less clear

9. 9 backup

10. 10 Status of Tracker Alignment Alignment algorithms (HIP, MillePede) both running with good turnaround Validation package including track  2, hit residuals, and geometry comparison standardized Experience during both CSA08 and Global Runs positive Alignment Workflow