linear collider vertex detector r&d
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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 - PowerPoint PPT PresentationTRANSCRIPT
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Natalie RoeUCSC Linear Collider WorkshopJune 27-29, 2002
Linear Collider Vertex Detector R&D
2 N. Roe LBNL LC Workshop 6/28/02
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
procurementsR&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
3 N. Roe LBNL LC Workshop 6/28/02
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 impactFirst 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
4 N. Roe LBNL LC Workshop 6/28/02
Requirements for an LC Vertex Detector
Accelerator-related requirements, such asBeam-pipe radius, thickness, machine stayclearRadiation levels & background ratesEvent rate and time structure of collisionsetc.
Physics requirements, eg vertex flavor tagging, driven by:Impact parameter resolutionTwo-track/two-hit separationEfficiency, fake track rateSolid angle coverageetc.
5 N. Roe LBNL LC Workshop 6/28/02
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
6 N. Roe LBNL LC Workshop 6/28/02
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?
7 N. Roe LBNL LC Workshop 6/28/02
NLC Bkgds
B=6T, no crossing angleB= ?See talk this morning by Maruyama
8 N. Roe LBNL LC Workshop 6/28/02
Quantifying Requirements: Accelerator constraints II
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
A
B
C
Tesla500 Tesla800 NLCA 200 ms 250 ms 8.3msB 337 ns 176ns 1.4 nsC 950 us 860us 266 nsC/B 2820 4886 190C/BA 14kHz 19.5kHz 23kHzL(1034) 3.4 5.8 2.0
9 N. Roe LBNL LC Workshop 6/28/02
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
10 N. Roe LBNL LC Workshop 6/28/02
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
11 N. Roe LBNL LC Workshop 6/28/02
Physics Requirements I
Flowdown of requirements:1) Science requirement: Precision on particular physics
quantities, eg error on Br(H-> cc)2) Performance requirement: high-level event parameter, eg
specified flavor tag purity at a given efficiency3) Detector requirement, eg impact parameter resolution or
tracking efficiency vs fake rate for a given detector subsystem
y A number of LC vertex detector studies have already been performed at all 3 levels.
y
12 N. Roe LBNL LC Workshop 6/28/02
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 )
13 N. Roe LBNL LC Workshop 6/28/02
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
€
σ =r2 ⋅σ1
r2 −r1
⎛
⎝ ⎜ ⎞
⎠ ⎟ ⊕
r1⋅σ2
r2 −r1
⎛
⎝ ⎜ ⎞
⎠ ⎟
σ1,2 =σms⊕σ pt; σms=0.014⋅ r X0
sin3/2θ ⋅βcp
14 N. Roe LBNL LC Workshop 6/28/02
Impact Parameter Resolution Studies - Schumm
dR
(cm
)
M.S. dominated
Pt resolution dominated
10 um
2-3 um
15 N. Roe LBNL LC Workshop 6/28/02
Impact parameter study
resolution ladder thickness beampipe radius outer radius
http://scipp.ucsc.edu/~schumm/talks/fnal2000/fnal2000_ag.ps
B. Schumm
“Standard L2” = 1.2 cm beampipe, 160 um Be, 5 um resolution
16 N. Roe LBNL LC Workshop 6/28/02
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 umMight 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
17 N. Roe LBNL LC Workshop 6/28/02
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?
A. Chou
18 N. Roe LBNL LC Workshop 6/28/02
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 (m) 5.0 5.0 3.0 3.0 4.0
H bb 3.8% 3.8% 3.8% 3,8% 3.8%
H 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 BRs - Oregon Study
Error on Higgs branching ratios is essentially independent of radius and resolution, with mild dependence for H-> cc
http://blueox.uoregon.edu/~jimbrau/LC/vxd-studies.PDF
Potter, Brau, Iwasaki
19 N. Roe LBNL LC Workshop 6/28/02
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.
20 N. Roe LBNL LC Workshop 6/28/02
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
21 N. Roe LBNL LC Workshop 6/28/02
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