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Outline

Outline. V.Kostioukhine, P.Nevski. A.Rozanov Motivations for improvements in b-layer Test layout for MC studies Additional b-layer at R=3.7 cm Material budgets Pixel Occupancy. 5 s. M H (GeV). b-tagging for SM Higgs. b-tagging role in: Discovery channel ttH with H-> bb

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Outline

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  1. Outline • V.Kostioukhine, P.Nevski. A.Rozanov • Motivations for improvements in b-layer • Test layout for MC studies • Additional b-layer at R=3.7 cm • Material budgets • Pixel Occupancy A.Rozanov CPPM 8.10.07 Highlights of b-layer upgrade workshop

  2. 5s MH(GeV) b-tagging for SM Higgs b-tagging role in: • Discovery channel • ttH with H-> bb • Supplementary channels • WH with H-> bb • ttH with H-> WW* • Background channels • ttjj • ttbb A.Rozanov CPPM 8.10.07 Highlights of b-layer upgrade workshop

  3. Performance contributions • Resolutions Rphi, Z • Pitch, cluster size, charge sharing (tilt,Lorenz),analog vs digital readout • Pattern recognition: efficiency, fakes, ambiguous hits, shared hits • Material: multiple scattering, secondary, conversions, b-layer radius A.Rozanov CPPM 8.10.07 Highlights of b-layer upgrade workshop

  4. Pileup • Pileup influence on b-tagging: • Wrong selection of primary vertex (dominant, but manageable in analysis…) • Tracks from pileup vertices in jets (with big Z impact parameters of course) Zvertex resolution for current ID is 50m <Nvrt> - mean number of pileup vertices in ±150m from primary vertex A.Rozanov CPPM 8.10.07 Highlights of b-layer upgrade workshop

  5. Pileup Minimal distance between primary and pileup vertices at Z=0 IR = 5.6cmNint = 23 IR = 2.1cmNint = 88 mm mm Better Z track and primary vertex resolution is needed to improve primary vertex reconstruction and rejection of pileup tracks (track - vertex association) A.Rozanov CPPM 8.10.07 Highlights of b-layer upgrade workshop

  6. Performances versus jet pT, η • Non-uniform performances: • even if very good at ||=0 and 50<P<150 GeV, still not satisfactory at ||~2 and P>250GeV • tagging b-jets can bias kinematics IP2D IP3D+SV1 εb= 60% IP2D IP3D+SV1 εb= 60% Worsening of b-tagging performance at ||>1 is due to material. Any way to improve? A.Rozanov CPPM 8.10.07 Highlights of b-layer upgrade workshop

  7. Pixel layout ||=2.0 112mm ||=2.5 A.Rozanov CPPM 8.10.07 Highlights of b-layer upgrade workshop

  8. Setup + software ATLSIM (Geant3 simulation) rel.10.0.6.DC1 model of ID (pixel).xKalmanOO from HEAD.Private version of b-tagging software. One pixel layer is added (Norbert’s proposal parameters):R=37mm16 staves (old DC1 design)Zpitch=250µm (no long pixels and gap between chips)Tilt=100Sensor thickness=250µmSensor and geometry are old  overlaps are not well defined (will be corrected soon) A.Rozanov CPPM 8.10.07 Highlights of b-layer upgrade workshop

  9. Layout Rb1= 37.0mmRb2= 50.5mm R1 = 88.5mmR2 = 122.5mm • To reduce thickness of new layer: • Support shell is absent • Thickness of stave (nonsensitive) is decreased A.Rozanov CPPM 8.10.07 Highlights of b-layer upgrade workshop

  10. Layout Material budget • To reduce thickness of new layer: • Old b-layer R=5.05 cm 2.2 % X0 • New b-layer R=3.7 cm 1.2 % X0 A.Rozanov CPPM 8.10.07 Highlights of b-layer upgrade workshop

  11. Layout Geant3 simulation of 3GeV pionin new pixel layout 4 hits in pixel det. A.Rozanov CPPM 8.10.07 Highlights of b-layer upgrade workshop

  12. Pixel occupancy at ||=0 Geant3 simulation of new pixel layout. 24 ev pileup (1034),IR=5.6cm, WH(120)µuu events. 16.4x60.0 mm2 sensor with 250µm Z pitch. Number of hits in module at ||=0 New layer R=37mm Existing layer R=50.5mm A.Rozanov CPPM 8.10.07 Highlights of b-layer upgrade workshop

  13. Pixel occupancy at ||=2.5 Geant3 simulation of new pixel layout. 24 ev pileup (1034),IR=5.6cm, WH(120)µuu events. 16.4x60.0 mm2 sensor with 250µm Z pitch. Number of hits in module at ||=2.5 New layer R=37mm Existing layer R=50.5mm A.Rozanov CPPM 8.10.07 Highlights of b-layer upgrade workshop

  14. Reconstruction ATRECON clusterisation and xKalmanOO from CVS HEAD.No special tuning for 4layer pixel.As reference a 3layer pixel (new b-layer removed) is used. Amount of silicon hits (Pixel+SCT) for “good” tracks3L 4L Additional hit is clearly visible  reconstruction sees additional layer A.Rozanov CPPM 8.10.07 Highlights of b-layer upgrade workshop

  15. Primary vertex (H(120)->uu events) XY(x100) resolution 3L 4L ~10% in XY ~30% in Z improvement in resolution due to 4th layer with 250µm pitch Z resolution 3L 4L A.Rozanov CPPM 8.10.07 Highlights of b-layer upgrade workshop

  16. Modified layout with single b-layer Rb1= 37.0mmRb2= absentR1 = 88.5mmR2 = 122.5mm A.Rozanov CPPM 8.10.07 Highlights of b-layer upgrade workshop

  17. Performance equivalences in old studies • Decrease of the b-layer radius from 5 cm to 4 cm (20% effect) • Decrease of the z-pitch in b-layer from 400 um to 200 um • Decrease of the material in b-layer by 0.6% • Loss of 1% / 2% pixel module/chip inefficiency in b-layer • Partial (2/3) missing the intermediate pixel layer (R=9cm) • Pile-up of 1034 cm2s-1 without muon pointing to primary vertex. A.Rozanov CPPM 8.10.07 Highlights of b-layer upgrade workshop

  18. Secondary vertices 2 mass for WH(120)->uu events3L 4L K0 peek is the same for both layouts  no big problems in pattern recognition R of interaction vertices (material) for WH(120)->uu events after conversion removal3L 4L Additional peek due to new layer is clear good ! Reconstructed number of interactions on beam pipe is smaller  problem ??? A.Rozanov CPPM 8.10.07 Highlights of b-layer upgrade workshop

  19. b-tagging: results Preliminary!!! WH(120)->uu(bb), no pileup, ATLFAST jets, reconstructed primary vertex.“Shared” pixel treatment switched off. Tracking performance seems ok for 4 layers case but b-tagging is worse comparing with current design. Track part of b-tagging is mainly responsible for worsening. Reconstruction tuning gives some improvement in b-tagging for 4L case. Not clear if it allows finally to overcome initial performance. A.Rozanov CPPM 8.10.07 Highlights of b-layer upgrade workshop

  20. b-tagging: illustration Track 2D impact significance with respect to primary vertex u-jets3L 4L Distributions are obtained AFTER conversions, K0/s and material interactions removal (although removal is based on reconstruction so not ideal…) A.Rozanov CPPM 8.10.07 Highlights of b-layer upgrade workshop

  21. b-tag:result for single b-layer(37mm) Preliminary!!! WH(120)->uu(bb), no pileup, ATLFAST jets,reconstructed primary vertex.“Shared” pixel treatment switched off. Track reconstruction program is the same in both cases A.Rozanov CPPM 8.10.07 Highlights of b-layer upgrade workshop

  22. ||>1 with single b-layer(37mm) WH(120)->uu(bb), no pileup, ATLFAST jets,reconstructed primary vertex. High ||>1 region.“Shared” pixel treatment switched off. Preliminary!!! • With upgraded 3L pixel: • Rejection in high || region is bigger • Drop of efficiency at high || is smaller Way to improve physics potential of pixel detector at high || ? (see previous talk) Less material in new layer (???). T0 cables are still in place. A.Rozanov CPPM 8.10.07 Highlights of b-layer upgrade workshop

  23. Limited access scenario D. Giugni BL Replacement Workshop - Sept 2007- 23 A.Rozanov CPPM 8.10.07 Highlights of b-layer upgrade workshop B-layer is replaced without removing all the SQPs and Disk. • This implies to remove one SQP per side, the beam pipe and the existing BL. The B-layer services are trapped in the gap between the barrel and the disk section and they have to be cut to extract the B-Layer. I have asked to evaluate what this means in term of contamination providing the quantity of activated material that is allowed to be dispersed in the air and on the surfaces. • What can be repaired is limited. • PP0 is accessible. Both leaks in the fitting and connector de-mate can be fixed. • Type0 cables are accessible and they can be repaired if the failure is outside the frame. • Optoboards located on the external OSP can be changed as well as the optoheaters • Disk capillaries can be changed if clough. Not the ones of the barrel • Most of the connectivity failures along the SQPs up to PP1 • What cannot be repaired are leaks inside the Disk or in the barrel bi-staves; substitute sector or bi-staves; fix connectivity failure inside frame volume; change most of the optoboard .

  24. Barrel access D. Giugni BL Replacement Workshop - Sept 2007- 24 A.Rozanov CPPM 8.10.07 Highlights of b-layer upgrade workshop B-layer is replaced disassembling all the SQP’s, the BPSS and the disk • What can be repaired is a lot. • All the SQPs can be refurbished. Accessing the OptoBoard and Optoheaters. • L1 and L2 Type0 cables are accessible up to the ends of the staves. • All the barrel fittings and many of the disk ones. • All the capillaries can be changed if clough. • What cannot be changed are bi-staves in L2 and L1 that would require a further disassembling

  25. Summary D. Giugni BL Replacement Workshop - Sept 2007- 25 A.Rozanov CPPM 8.10.07 Highlights of b-layer upgrade workshop • Limited access 5.5 months • Barrel access 9.5 months • Local Support access 18.5 months

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