1. Track-based Muon Alignment Status Yuriy Pakhotin On behalf of Muon Alignment Group Muon Barrel Workshop May 5th, 2011 https://indico.cern.ch/conferenceDisplay.py?confId=137060

2. Outline • Updates to Muon Alignment with “twist-free” Tracker • Fix a problem with missing hits in stations 3 and 4 • Switch from Global Muon Tracks to Tracker Muons • Alignment with full 2010 data almost done • Collisions • Cosmics • Beam Halo • Alignment with 2011 data in development

3. List of Detailed Reportssince last Barrel Workshop • Muon Alignment Meeting, Fri Feb 25th, 2011 • http://indico.cern.ch/conferenceDisplay.py?confId=128860 • “TB muon alignment with twist-free tracker” by AysenTatarinov • Muon Alignment Meeting, Fri Mar 11th, 2011 • http://indico.cern.ch/conferenceDisplay.py?confId=130953 • “CSC disk update with untwisted tracker” by VadimKhotilovich • “Muon Reco Validation for new endcap alignment” by Luca Scodellaro • Muon DPG Meeting, Mon Mar 14th, 2011 • http://indico.cern.ch/conferenceDisplay.py?confId=130897 • “Barrel muon alignment with twist-free tracker” by AysenTatarinov • “CSC disk update with untwisted tracker” by VadimKhotilovich • Update on muon alignment, Tue March 15th, 2011 • http://indico.cern.ch/conferenceDisplay.py?confId=126162#6 • “Update on muon alignment” by Yuriy Pakhotin

4. Twist in the EOY Tracker Geometry • Twist effect in End-Of-Year (EOY) Tracker geometry • E.g. visible in reconstructed Zmm mass bias vsη • “Twist-free” Tracker geometry is signed-off on Feb 23rd, 2011 at the Joint PVT/PO Meeting • http://indico.cern.ch/conferenceDisplay.py?confId=128328 from G. Flucke (DESY) for the TK Alignment group Twist-free geometry EOY geometry

5. Muon Alignment in DT Wheels with “twist-free” Tracker Hardware vs. Track-based alignment comparison from A. Tatarinov (Texas A&M) Seeded by EOY Tracker geometry: “TWIST” Seeded by “twist-free” Tracker geometry: NO “TWIST” twist angle Twist effect in Barrel is significantly reduced! Current geometry based on HW, no corrections are needed

6. Update to CSC Alignment with “twist-free” Tracker • Use latest “twist-free” Tracker Alignment as input • CSC Rings are aligned as rigid bodies • Chambers within rings already aligned • Updated GPRs for tracker and muon system • Compare CSC Ring positions in two geometries • New “minus” EOY • Observations: • Small shifts (≈ 0.3 mm)in X and Y • Due to changes in GPR • Large twist (φZ ≈ ±1 mrad) in opposite directions in +- endcaps • Effect of the tracker “untwisting” • Important to keep CSC alignment in sync with • Tracker geometry • CSC Alignment was signed off X from V. Khotilovich (Texas A&M) Y φZ ≈2 mrad twist angle

7. Missing Hits in Station 3 and 4 • regular gaps in distributions of global phi of global muons' track hits in stations 3 and 4 were observed • muons pT > 20 GeV • Sample: /Mu/Run2010B-SingleMu-Dec22Skim_v2/RECO gaps

8. Missing Hits in Station 3 and 4 cont’d • Only global muons tracks have missed hits. STA muons were fine. Standalone Global

9. Missing Hits in Station 3 and 4 cont’d • The problem was fixed recently • RecoMuon/GlobalTrackingTool/GlobalTrajectoryBuilderBase.cc • Ad-hoc sorters removed • New code is in CMSSW >4.2.X No gaps

10. Alignment with Tracker Muons • Global muons’ tracks were previously used • Large uncertainties were assigned to hits in muons system to exclude bias in alignment • Now we are switching to Tracker muons’ tracks • Substantial change in code -- done • Validation is in progress • median plots show residuals RMS slightly better for tracker muons w/ TRK muons w/ GLB muons

11. Updated Track-based Alignment • Alignment with full 2010 data almost done • Samples: • Collisions • Cosmics • Beam Halo • New re-reco of 2010 data is just became available • A few minor issues need to be resolved • Alignment with new 2011 data is in development • Samples • Collisions and Cosmics • No beam halo • Plans to include realistic APEs from covariance matrix

12. Conclusion • Twist free Tracker geometry resolved the long standing “twist problem” in muon alignment • Updated CSC alignment is in-sync with tracker • Missing hits in DT stations 3 and 4 fixed • Tracker muons’ tracks are used in TB alignment • New alignment with re-reco 2010 data is almost done • Alignment with new 2011 data is in development