First Reconstruction Results on the Alignment of Muon Endcap Chambers in the CMS Experiment at CERN S. Guragain, G. Baksay, M. Hohlmann Florida Tech 74 th Annual meeting of SESAPS, Nashville, TN, Nov 8-10, 2007

11/08/2007 S. Guragain - SESAPS meeting, Tennessee 2 CMS detector of CERN CMS solenoid -13 m long Magnetic field - 4 Tesla Total weight t Overall diameter -15 m Overall length m Yokes Muon Endcaps ME+1 ME+2 ME+3 ME+4 ME - Z+ Compact Muon Solenoid

11/08/2007 S. Guragain - SESAPS meeting, Tennessee 3 A part of CMS 2 Crosshair Lasers (adjustable) Ref. DCOPS Chamber DCOPS’s Transfer Line DCOPS Z-tube Z-sensors Transfer Plate Clinometer Mounting Tower ME+2 SLM Back Chamber R-sensor Laser beam Laser on ! Z CMS Rphi CM S

11/08/2007 S. Guragain - SESAPS meeting, Tennessee 4 Full Reconstruction Model R-sensors Z-sensors Note: only small sample of analog sensors shown Clinometers Transfer plate DCOPS’s Straight Line Monitors (SLMs) and Transfer lines Lasers SLM currently under study (ME+2 SLM 2-5) Lasers Chamber resolution 75 micron for ME1/2 and 150micron for other. The system monitors the positions of CSCs relative to each other and to the MABs

11/08/2007 S. Guragain - SESAPS meeting, Tennessee 5 Basic strategy Fit DCOPS data at B=0T and reconstruct DCOPS and CSC positions using COCOA (CMS Object-oriented Code for Optical Alignment) Check B=0T reco results for one SLM against photogrammetry (PG) in full detail and with great care until we can trust the reconstruction Quantify precisions and accuracies Reconstruct DCOPS & CSC positions at B=4T Apply lessons learned to reco of other SLMs

11/08/2007 S. Guragain - SESAPS meeting, Tennessee 6 Simultaneous fit in z CMS for two lasers in ME+2 SLM2-5 at B=0T DCOPS CCDs B=0T Laser hits (shifted to the sides of CCDs for display) CCD2 CCD4 CCD2 CCD4 fitted position First CCD pixels Simultaneous fitting of 2 lasers with hits that overlap on 4 central DCOPS’s is now working ! Ref. CCD bad hits not used in fit Note: In MTCC 2006 the lasers were tilted towards the CSCs on purpose to compensate for disk bending at B=4T ! laser line fit

11/08/2007 S. Guragain - SESAPS meeting, Tennessee 7 Fit Residuals Precision in z CMS (“z-resolution”) ≈ 60  m

11/08/2007 S. Guragain - SESAPS meeting, Tennessee 8 Dowel pins Reconstructed tops of CSC Alignment pins Reconstructed tops of DCOPS boxes First CCD pixels Reconstructed positions of outer CSC PCB skins B=0T CCDs PG of TPs determines global z CMS position of entire system Reconstructed DCOPS & CSC Positions and their Precision Note: In this coordinate system the DCOPS are “up-side-down” (ME+2 DCOPS tops are at smaller z CMS )  z reco ~ 270  m Shim delta New shim New shim

11/08/2007 S. Guragain - SESAPS meeting, Tennessee 9 Now, accuracy …

11/08/2007 S. Guragain - SESAPS meeting, Tennessee 10 Solid triangles: Reconstructed tops of CSC Alignment pins Solid triangles: Reconstructed tops of DCOPS boxes First CCD pixels Reconstructed positions of outer CSC PCB skins B=0T CCDs PG of TPs determines global z CMS position of entire system Accuracy check of ABSOLUTE positions against PG at B=0T Open triangles: PG measurement of tops of DCOPS boxes Open triangles: PG meas. of CSC Alignment pins PG measurements of coded targets on outer CSC PCB skins Reco and PG now match well !!! Perfect ! (no PG avail.)

11/08/2007 S. Guragain - SESAPS meeting, Tennessee 11 Discrepancy in Z between PG and Fitted positions 683 micron

11/08/2007 S. Guragain - SESAPS meeting, Tennessee 12 Reconstruction of z CMS for CSCs in ME+2 SLM2-5 at B=4T B=4T B=0T fit positions B=4T fitted CSC positions Disk bending is reconstructed ! This assumes (incorrectly) that the TP’s do not shift in z & do not rotate! ~ 13mm

11/08/2007 S. Guragain - SESAPS meeting, Tennessee 13 Summary Reconstruction of z CMS coordinate is working Z-resolution & Sensitivity to relative motion ≈ 60  m Z-precision of reconstructed CSC centers ≈ 270  m Z-accuracy of reconstruction ≈ 680  m (Comparison with Photogrammetry data) Accuracy required by design 1 mm Disk bending at B=4T is reconstructed THANKS

11/08/2007 S. Guragain - SESAPS meeting, Tennessee 14 Back up slides

11/08/2007 S. Guragain - SESAPS meeting, Tennessee 15 ME+2 Disk

11/08/2007 S. Guragain - SESAPS meeting, Tennessee 16 Beam Profiles measured with CCDs 2 & 4 in ME+2 SLM2-5 for both Lasers Laser Beam Profiles supplied by Jim Bellinger Pt.5 Pt.2 One MTCC2 alignment event: Nov 3, :01:16:48 CCDs 4 Laser 2 CCDs 2 in 10 DCOPS Good hits ! Laser 2 Laser 5

11/08/2007 S. Guragain - SESAPS meeting, Tennessee 17 Reconstructing ABSOLUTE CSC z CMS - coordinates via DCOPS geometry… z-coordinate of first CCD pixel (14  m/pixel × 1024 pixels) z-reference surface for DCOPS dowel pin (new!) nominal z CMS - position for SLM updated CAD Drawing by Dave Eartly – 10/15/07 CCD Top of DCOPS box DCOPS foot Dowel pin (precision element) center Allowed Laser Range CCDs 2 & 4 All dimensions in mm DCOPS Side View +

11/08/2007 S. Guragain - SESAPS meeting, Tennessee 18 z-coordinate of first CCD pixel z-reference surface for DCOPS dowel pin nominal z CMS - position for SLM CCD Top of DCOPS box z-coord. of PG Target on top of DCOPS box Shim Mounting plate Mounting bar DCOPS foot top CSC PCB panel updated CAD Drawing by Dave Eartly – 10/15/07 CSC z-reference surface for al. reco (new!) coded PG target lives here ! CSC frame … CSC geometry…

11/08/2007 S. Guragain - SESAPS meeting, Tennessee 19 …and Transfer Plate (TP) geometry TP ref. surface (also for PG) SLM Reference DCOPS Transfer Line DCOPS Laser 6.73 (newly found shim !) updated CAD Drawing by Dave Eartly – 10/17/07

11/08/2007 S. Guragain - SESAPS meeting, Tennessee 20 Sanity check on Precision as returned by Reconstruction All errors in microns All tolerances In this column under review !  Precision dominated by mechanical tolerances and not by spread of laser hits in fit (60  m res.) !  ok !

11/08/2007 S. Guragain - SESAPS meeting, Tennessee 21 Effect of missing hits This Example: Turn one good hit into a bad hit on two separate DCOPS on the same chamber Result: This has only a small effect on the overall fit and reconstructed positions ! Simulate effect of missing laser hits (e.g. due to shadowing) on the reco results by manually inflating errors on good hits

11/08/2007 S. Guragain - SESAPS meeting, Tennessee 22 Effect of missing hits cont’d