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Update on Global Alignment Steven Blusk Syracuse University

Update on Global Alignment Steven Blusk Syracuse University. Preface. The LHCb detector alignment will require several steps. A sensible scenario is: Internal Alignment of the VELO (first halves, then to each other) Internal alignment of T-Stations (IT, OT and IT-to-OT)

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Update on Global Alignment Steven Blusk Syracuse University

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  1. Update on GlobalAlignmentSteven BluskSyracuse University

  2. Preface • The LHCb detector alignment will require several steps. A sensiblescenario is: • Internal Alignment of the VELO (first halves, then to each other) • Internal alignment of T-Stations (IT, OT and IT-to-OT) • Relative alignment of VELO to T-Stations • Alignment of TT to VELO-T Station system • Alignment of ECAL & HCAL to tracking system • Alignment of MUON to tracking system • Alignment of RICH to tracking system The internal alignment tasks are being addressed by various groups. Here, I present a plan and details for Step 3. Simulations consistent of 5000 event samples of min bias usingGauss v22r1, Boole v10r3, Brunel v28r2

  3. Relative VELO-to-T-Station Alignment • After internal alignment of each, there are in principle 9 global transformations between the two systems: • 3 translations (X,Y,Z) • 3 rotations (a,b,g) • 3 scale factors (Xscale, Yscale, Zscale ) • In practice, Xscale, Yscale are highly constrained by the interwire/strip spacing. Therefore there are realistically 7 global parameters between the two systems. • Align the VELO to the T-Stations by matching segments at the center of the magnet (Zmag).. Pattern recognition done independently in each system. • They can all be measured using MAGNET OFF data: • DX: Mean of XVELO-XT at Zmag. • DY: Mean of YVELO-YT at Zmag. • DZ: Mean of (XVELO-XT)/tanqXVELO at Zmag. • Da: Mean of tanqYVELO-tanqYT. • Db: Mean of tanqXVELO-tanqXT • Dg: Mean difference in azimuthal angle fVELO-fT at Zmag. • Zscale: Mean of (tanqXVELO-tanqXT) / tanqXVELO

  4. Method Details • We use a single kick approximation to the field, where the kickoccurs at the effective center of the magnet (Zmag). • This is only an approximation, and in general Zmag is a function of the track’s X,Y slopes and momentum. • To minimize dependence, we can require high momentum, low angle trackssince we are only seeking global alignment parameters. We require: • p > 20 GeV/c (no p cut for B=0, for the moment) • VELO angles < 100 mrad • TX-seed angle < 200 mrad (Ty–seed constrained since Py ~unchanged) • Zmag is determined using simulation, with “perfect geometry” and field045.cdf. We map out using the straight line intersection of T-seed and VELO tracks: • Zmag = 526.7 cm, and has a mild dependence on X angle. • We correct for it, but it’s not critical to determine global offsets. • Correction to Y-slope in T-Station for change in Pz.

  5. Results with Perfect Geometry: B=0 No Zmag,since nobending DSlopeY Zmag All meansare consistentwith zero ! DX at Zmag DY at Zmag DZ Dg at Zmag

  6. 1 mm X Shift of VELO: B=0 No Zmag,since nobending DSlopeY Zmag <DX>=(942±31) mm DX at Zmag DY at Zmag All other meansconsistentwith zero ! DZ Dg at Zmag

  7. 5 mm Y Shift of VELO: B=0 DSlopeY Zmag <DY>=(4981±55) mm DX at Zmag DY at Zmag All other meansconsistentwith zero ! DZ Dg at Zmag

  8. 1 cm Z Shift of VELO: B=0 All other meansconsistentwith zero ! DSlopeY Zmag DX at Zmag DY at Zmag <DZ>=(1.25±0.12) cm DZ Dg at Zmag

  9. 2 mrad Z-RotationVELO: B=0 All other meansconsistentwith zero ! DSlopeY Zmag DX at Zmag DY at Zmag <Dg>=(2.03±0.16) mrad DZ Dg at Zmag

  10. Results with Perfect Geometry: B=Nom DSlopeY Zmag DX at Zmag DY at Zmag <Dg>=(0.47±0.31) mrad All meansconsistentwith zero ! DZ Dg at Zmag

  11. 1 mm X Shift of VELO: B=Nom DSlopeY Zmag <DX>=(1036±23)mm DX at Zmag DY at Zmag All other meansconsistentwith zero ! DZ Dg at Zmag

  12. 5 mm Y Shift of VELO: B=Nom DSlopeY Zmag <DY>=(5049±71) mm DX at Zmag DY at Zmag All other meansconsistentwith zero ! DZ Dg at Zmag

  13. 1 cm Z Shift of VELO: B=Nom All other meansconsistentwith zero ! DSlopeY Zmag DX at Zmag DY at Zmag <DZ>=(1.07±0.11) cm DZ Dg at Zmag

  14. 2 mrad Z-RotationVELO: B=Nom All other meansconsistentwith zero ! DSlopeY Zmag DX at Zmag DY at Zmag <Dg>=(2.56±0.30) mrad DZ Dg at Zmag

  15. Several ShiftsVELO: B=Nom DSlopeY Zmag In: DX= - 250 mm Out: DX= - (249±23)mm In: DY= 250 mm Out: DY= (188±50)mm DX at Zmag DY at Zmag In: Dg = 2 mrad Out: Dg = (2.38±0.33)mm In: DZ = 4 mm Out: DZ = (3.1±1.1) mm DZ Dg at Zmag

  16. Summarizing Still need to check rotations around X,Y axes and Z-scale but don’t expect any surprises

  17. Conclusions • Matching at the center of magnet appears to provide robustestimate of relative alignment between VELO and T-Stations. • 5000 min bias events gives reasonably good precision on offsets(Scale by 1/N to get a given precision) • Still need to check Da and Db and Z-scale, but don’t expectany surprises. • Document in progress. Full description of LHCb alignment needsto be put together. This is one piece of it. • Migrate (PAW) code to ROOT-based GaudiAlgorithm. Many thanks again to Matt , Eduardo, Juan and Marco Cattaneo for lots of help with software issues…

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