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Linear Collider Vertex Detector R&D

Linear Collider Vertex Detector R&D. Natalie Roe UCSC Linear Collider Workshop June 27-29, 2002. R&D: General Goals & Strategy. R&D should be undertaken to mitigate risk and ensure a project will succeed

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Linear Collider Vertex Detector R&D

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  1. Linear Collider Vertex Detector R&D Natalie Roe UCSC Linear Collider Workshop June 27-29, 2002

  2. R&D: General Goals & Strategy • R&D should be undertaken to mitigate risk and ensure a project will succeed • Technical risk for new, unproven techniques or significant extensions of existing methods • Schedule risk for long-lead development or procurements • R&D strategy: identify areas of technical or schedule risk with biggest physics impact • Focus on most critical areas needing early R&D investment to ensure the project’s success and to maximize the physics reach N. Roe LBNL LC Workshop 6/28/02

  3. What type of R&D is required for LC Detectors? • Hard to argue schedule risk at this stage… • There is time for new technical developments with significant physics impact • First step is to write down machine constraints and physics-driven requirements • Next, devise a focused R&D plan to address the technical issues associated with the requirements that: • a) have biggest physics impact, and • b) are most challenging N. Roe LBNL LC Workshop 6/28/02

  4. Requirements for an LC Vertex Detector • Accelerator-related requirements, such as • Beam-pipe radius, thickness, machine stayclear • Radiation levels & background rates • Event rate and time structure of collisions • etc. • Physics requirements, eg vertex flavor tagging, driven by: • Impact parameter resolution • Two-track/two-hit separation • Efficiency, fake track rate • Solid angle coverage • etc. N. Roe LBNL LC Workshop 6/28/02

  5. Quantifying Requirements: Accelerator constraints • Machine design is not yet finalized • Detailed design studies exist for several machines - consider worst case parameters • Experience suggests conservative assumptions eg, radiation levels generally get worse with more realistic machine studies, bkgds go up etc. • Critical design areas may require iteration with accelerator experts, additional efforts on machine simulations N. Roe LBNL LC Workshop 6/28/02

  6. Quantifying Requirements: Accelerator constraints I • Beam pipe radius: determined by beamstrahlung and synchrotron radiation backgrounds. Present thinking: • NLC: r = 1 cm for z = ± 2.5 cm, then increases to 2.2 cm • Tesla: r = 1.4 cm • Radiation & background rates: • Tesla: • beam-beam e+e- pairs produce 0.03 hits/mm2/BX, resulting in ~20kRad/yr ionizing radiation for B= 4T and r = 1.5 cm • Neutron fluence ~ 109 1 MeV neutrons/cm2/yr • NLC: • beam-beam e+e- pairs produce 3 hits/mm2/train =0.015 hits/mm/BX at B=3T and r = 1.2 cm • Neutron fluence estimates vary from 107 to 1011 n/cm2/year Maruyama - 2.3 x 109 n/cm2/year • What about beam gas backgrounds? N. Roe LBNL LC Workshop 6/28/02

  7. NLC Bkgds B=6T, no crossing angle B= ? See talk this morning by Maruyama N. Roe LBNL LC Workshop 6/28/02

  8. Quantifying Requirements: Accelerator constraints II Tesla500 Tesla800 NLC A 200 ms 250 ms 8.3ms B 337 ns 176ns 1.4 ns C 950 us 860us 266 ns C/B 2820 4886 190 C/BA 14kHz 19.5kHz 23kHz L(1034) 3.4 5.8 2.0 • Time Structure & Event Rates • Layer 1 hit occupancies (bkgd dominated): • At NLC 190 x 0.015 hits/mm2/BX = 2.85 hits/mm2/train = 1 x 10-3 occupancy for 20x20um pixels => read out between bunch trains • At Tesla 2820 x 0.030 hits/mm2/BX = 84.5 hits/mm2/train = 3.4 % occ for 20x20 um pixel => readout during train B C A N. Roe LBNL LC Workshop 6/28/02

  9. Reality Check: NLC vs Tesla background rates • Tesla = 0.03 hits/mm2/BX at 4T, r=1.5 mm • NLC = 0.015 hits/mm2/BX at 3T, r=1.2 mm • Why are NLC bkgds lower with smaller B field and radius? • Bkgds/BX should be proportional to lumi/BX • Tesla: 3.4x1034 / 14kHz • NLC: 2x1034 / 23kHz • Factor of 3 lower lumi/BX at NLC => compensated for by lower B and r • More detailed comparisons needed, eg compare rates at same B field and radius. • Understand beamgas and synchrotron backgrounds and compare N. Roe LBNL LC Workshop 6/28/02

  10. Quantifying Requirements: Accelerator constraints III • Beam pipe thickness (scale: 100 um of Si ~ 0.1%X0): • Tesla studies assume a beampipe of ~ 0.25 mm Be = 0.07%X0 • Matches first detector layer thickness of 0.06% X0 • NLC studies: assumptions ranging from 0.160 - 0.180 mm Be(?) • NLC beampipe has stepped radius from 1.2 -> 2.4 cm to avoid backgrounds - does this create problems with showering? • Multiple scattering in beampipe sets scale for thickness of first detector layer and for point resolution at low p • Radius and thickness of beampipe are critical inputs for vertex detector; think of beampipe as part of detector N. Roe LBNL LC Workshop 6/28/02

  11. Physics Requirements I • Flowdown of requirements: • Science requirement: Precision on particular physics quantities, eg error on Br(H-> cc) • Performance requirement: high-level event parameter, eg specified flavor tag purity at a given efficiency • Detector requirement, eg impact parameter resolution or tracking efficiency vs fake rate for a given detector subsystem • A number of LC vertex detector studies have already been performed at all 3 levels. N. Roe LBNL LC Workshop 6/28/02

  12. Selected Previous Vertex Performance Studies • Sinev:http://blueox.uoregon.edu/~jimbrau/talks/IEEE-99/ieee99.pdf • Abe(ghost tracks): http://www.slac.stanford.edu/~toshi/LCDstudy/toshi_ghost.pdf • Schumm (vertex parameters): http://scipp.ucsc.edu/~schumm/talks/fnal2000/fnal2000_ag.ps • Oregon vertex detector parameters study: http://blueox.uoregon.edu/~jimbrau/LC/vxd-studies.PDF • Chou (H->cc): http://www-sldnt.slac.stanford.edu/nld/meetings/ChicagoJan2002/BRHccJan8.pdf • Potter et al (Higgs branching ratios ): http://www.slac.stanford.edu/econf/C010630/forweb/P118_potter.pdf • Iwasaki - top: http://www.slac.stanford.edu/~masako/LC_study/Chicago2002/Top.pdf • Walkowiak:http://www.slac.stanford.edu/~walkowia/lcd/talks/ chicago2002/lcChicago010802-1.pdf • LCFI studies : ( http://hep.ph.liv.ac.uk/~green/lcfi/home.html ) N. Roe LBNL LC Workshop 6/28/02

  13. Physics Requirements II • Impact parameter resolution: • Simplified formula for i.p. resolution in 2 layer device with measurements at r1,r2 and errors  : • Dominated by resolution of first hit • Multiple scattering dominates for low momenta; material in beampipe and first detector layer must be minimized, along with radius of 1st hit • Intrinsic point resolution dominates at high momenta - includes misalignment effects N. Roe LBNL LC Workshop 6/28/02

  14. Impact Parameter Resolution Studies - Schumm 10 um Pt resolution dominated dR (cm) M.S. dominated 2-3 um N. Roe LBNL LC Workshop 6/28/02

  15. Impact parameter study • resolution • ladder thickness • beampipe radius • outer radius http://scipp.ucsc.edu/ ~schumm/talks/fnal2000/ fnal2000_ag.ps B. Schumm N. Roe LBNL LC Workshop 6/28/02 “Standard L2” = 1.2 cm beampipe, 160 um Be, 5 um resolution

  16. How does i.p. resolution affect flavor tagging? • Compare i.p. resolution to typical impact parameters at LC • For B decay products, i.p. ~ 300 um>>10 um • B-tagging should not depend strongly on pt resolution, beampipe radius or thickness • For charm decay products, i.p. ~ 80-100 um • Might see mild dependence • To correctly assign tracks to both b and c vertices to determine charge or mass will be more challenging • Needs a level 2/level 3 study N. Roe LBNL LC Workshop 6/28/02

  17. Study of Charm Tagging • Mild detector dependence: 15% change going from 10 um, 1.0%X0 to 1 um, 0.03%X0 detector • Beampipe radius = 1 cm • What was the beampipe thickness? • What bkgd levels? N. Roe LBNL LC Workshop 6/28/02 A. Chou

  18. Error on Higgs BRs - Oregon Study MH = 140 GeV/c2 , s = 500 GeV, L = 500 fb-1 RINNER(cm) 1.2 2.4 1.2 2.4 1.2 hit res (mm) 5.0 5.0 3.0 3.0 4.0 H  bb 3.8% 3.8% 3.8% 3,8% 3.8% H  tt 10% 10% 10% 10% 10% H  cc 46% 47% 42% 46% 42% H  gg 23% 22% 22% 22% 22% H  WW* 3.5% 3.5% 3.5% 3.5% 3.5% Error on Higgs branching ratios is essentially independent of radius and resolution, with mild dependence for H-> cc Potter, Brau, Iwasaki http://blueox.uoregon.edu/ ~jimbrau/LC/vxd-studies.PDF N. Roe LBNL LC Workshop 6/28/02

  19. Vertex R&D - paper studies & simulations • Write down assumptions for NLC/Tesla/JLC beampipe, backgrounds, radiation levels; compare/rationalize different results, get improved estimates if possible (=>run accelerator simulations) • Consider dependence of i.p. resolution on beampipe thickness as well as detector thickness; engineering study of beampipe construction? • Consider effects of material at large radius as well (cryostat can decouple vertex from outer tracking, reduce effective lever arm for tracking) • Consider design where L1 is special: thinner, faster readout, better resolution. (may want L2 also for backup) • Document a set of science-driven requirements (goals) for vertex detector performance, with a clear link from specific measurements to the required performance parameters. N. Roe LBNL LC Workshop 6/28/02

  20. R&D: Hands-on studies • Leading candidates: CCDs, hybrid pixels, active pixels … + time to develop new ideas! • General areas for R&D • Radiation hardness • Readout speed, especially in Tesla context • Minimizing material thickness including mechanical structures and beampipe N. Roe LBNL LC Workshop 6/28/02

  21. Summary • There are interesting vertex detector issues to address both in simulation and in hands-on R&D • To coordinate US efforts, please provide a brief description, list of participants and proposed budget • Should aim to cooperate on global level with international partners N. Roe LBNL LC Workshop 6/28/02

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