SiD Expectations from the Design Study

1
SiDExpectations from the Design Study

• Motivation
• What We Need!
• Technical efforts
• Status

2
SiD Motivation

• SiD is an attempt to interest the US HEP
  community, and the international community, in
  the experimental challenges of a LC.
• SiD represents an attempt to design a
  comprehensive LC detector, aggressive in
  performance but constrained in cost.
• SiD attempts to optimize the integrated physics
  performance capabilities of its subsystems.
• SiD might be considered a first step towards
  being one of the two detectors at the LC, but its
  development is substantially behind TESLA.
• SiD addresses warm technology advantages and
  challenges but could handle cold. We shall soon
  see!
• The design study should evolve the present
  concept of SiD towards a more complete and
  optimized design.

3
Nominal SiD Detector Requirements

• a) Two-jet mass resolution comparable to the
  natural widths of W and Z for an unambiguous
  identification of the final states.
• b) Excellent flavor-tagging efficiency and purity
  (for both b- and c-quarks, and hopefully also for
  s-quarks).
• c) Momentum resolution capable of reconstructing
  the recoil-mass to di-muons in Higgs-strahlung
  with resolution better than beam-energy spread .
• d) Hermeticity (both crack-less and coverage to
  very forward angles) to precisely determine the
  missing momentum.
• e) Timing resolution capable of tagging
  bunch-crossings to suppress backgrounds in
  calorimeter and tracker.
• f) Very forward calorimetry that resolves each
  bunch in the train for veto capability.
• This is the standard doctrine is it correct and
  complete?

4
SiD (Silicon Detector)

• Conceived as a high performance detector for the
  LC
• Reasonably uncompromised performance
• But
• Constrained Rational cost
• Detectors will get about 10
• of the LC budget 2 detectors,
• so 350 M each

• Accept the notion that excellent energy flow
  calorimetry is required, and explore optimization
  of a Tungsten-Silicon EMCal and the implications
  for the detector architecture

This is the monster assumption of SiD (and
TESLA!)
5
Crude Cost Breakdown
6
Crude Cost Trends
7
Architecture arguments

• Silicon is expensive, so limit area by limiting
  radius (and length)
• Get back BR2 by pushing B (5T)
• Maintain tracking resolution by using silicon
  strips
• Buy safety margin for VXD with the 5T B-field.
• Keep track finding by using 5 VXD space points to
  determine track tracker measures sagitta.

8
Knees

• During the SSC era, the SSC PAC asked the
  detector collaborations to justify their design
  choices where possible by understanding the
  quality of detector performance as a function of
  a critical detector parameter. Ideally,
  quantities like overall errors on an important
  physics process would flatten out as a function
  of, say, calorimeter resolution, and there would
  be a rational argument for how good the
  resolution should be.
• We need similar analyses for the major parameters
  of SiD EMCal radius and B are probably at the
  top of the list, along with justifying E-Flow
  calorimetry.
• We need to select physics processes for this
  study.
• We are not constrained to design detector around
  these knees, but we should know where they are!

9
SiD Configuration

Scale of EMCal Vertex Detector
10
Vertex Detectors
Tesla
SiD
Extend 5 layer tracking over max O ?improve O
Coverage, improve sxy, srz 5 CCD layers
.97 (vs. .90 TDR VXD) 4 CCD layers
.98 (vs. .93 TDR VXD) Minimize CCD
area/cost ? Shorten Barrel CCDs to 12.5 cm (vs.
25.0cm) Thin the CCD barrel endplate ? a single
300 ?µm Si disk for self supporting

• Design CCDs for
• Optimal shape 2 x 12 cm
• Multiple (18) ReadOut nodes for fast readout
• Thin - 100 µ
• Improved radiation hardness
• Low power
• Readout ASIC
• No connectors, cables, output to F.O.
• High reliability
• Increased RO speed and lower power compared to
  SLD VXD3
• Detailed (preliminary) spec coming along

11
Vertex Detector Questions

• The beam pipe could be made very thin with some
  serious engineering Does the physics justify
  the effort?
• The CCDs could probably be thinned to 50 µm
  Does the physics justify the effort?
• The CCDs could probably be supported by
  stretching from their ends same question.
• The present nominal radius of the beampipe is 1.0
  cm. This is probably a stretch for the machine.
  Is it justified?
• The preliminary impression is that the answers
  are No! They need work!

12
Silicon Tracker

• SLC/SLD Prejudice Silicon is robust against
  machine mishaps wires gas are not.
• Silicon should be relatively easy to commission
  no td relations, easily modeled Lorentz angle,
  stable geometry and constants.
• SiD as a system should have superb track finding
• 5 layers of highly pixellated CCDs
• 5 layers of Si strips, outer layer measures 2
  coordinates
• EMCal provides extra tracking for Vee finding -
  1mm resolution!
• Simulation Studies
• Pattern recognition (S. Wagner, N. Sinev)
• Occupancies (T. Maruyama)
• ?? backgrounds (T. Barklow)
• Geometry optimization (R. Partridge - Brown)
• All studies so far are encouraging. (Note very
  forward rates are high, and required segmentation
  is not yet designed.

13
Illustration of bunch timing tag
Yellow muons Red electrons Green
charged pions
Dashed Blue photons with E gt 100 MeV
full train (56 events) 454 GeV
detected energy 100 detected charged
tracks
1 bunch crossing
T. Barklow
14
First attempt - Make Structure of Long Ladders

• Readout half ladders from ends.
• Wire bond 10 cm square detectors in daisy chain
  as in GLAST.
• Minimal electronics and power pulsing make gas
  cooling easy. No liquids, leaks or associated
  mass.
• Problems
• Timing tag seems impossible.
• Occupancies forward

15
Evolve!

• Ditch (romantic) notion of long ladders and read
  out each detector.
• Detector has signals routed to rectangular grid
  for bump bonding to detector, analogous to design
  for Si-W Calorimeter.
• Bunch separation timing capability, better
  segmentation and occupancy, better S/N.
• Replace individual ladders with composite,
  monolithic cylinder with detectors mounted to
  surface.

Strip Detector
Bypass Caps
Thin Kapton Cable
Readout Chip
16
Thickness Budget (Rough!)
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Momenter Questions

• Are there any serious problems with track finding
  (using VXD EMCal)? (Barrel is 5 axial layers,
  segmented 13 cm.)
• Is the 1.25 m radius optimal? What about the
  length?
• Is 5 T B optimal?
• Is there motivation to try to go thinner? Is
  there a knee in the physics performance vs
  multiple scattering?

18
SiD EMCal Concept
Longitudinal
19
Wafer and readout chip
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SiD Si/W Features

• Current configuration
• 5 mm pixels
• 30 layers
• 20 x 5/7 X0
• 10 x 10/7 X0

• 1000 channels per readout chip
• Compact thin gap 1mm
• Moliere radius 9mm ? 14 mm
• Cost nearly independent of transverse
  segmentation
• Power cycling only passive cooling required
• Dynamic range OK
• BunchTiming in design
• Low capacitance
• Good S/N
• Correct for charge slewing/outliers
• 5 ns s per (independent) measurement

21
Components in hand

• Tungsten
• Rolled 2.5mm
• 1mm still OK
• Very good quality
• lt 30 µm variations
• 92.5 W alloy
• Pieces up to 1m long possible

• Silicon
• Hamamatsu detectors
• Should have first lab measurements soon

22
EMCal Questions

• Is an (expensive) Si-W tracking EMCal justified
  by the physics? Does E-Flow really work? It gives
  good but not great energy resolution what about
  an EMCal with crystals with superb energy
  resolution? Crystals with some longitudinal
  segmentation?
• Is there a useful Figure of Merit for E-Flow
  calorimetry? (My present favorite is
  BR2/(smeff?spixel)2x(smeff ??rsamp)
• Is radius of 1.25 m optimal? Is 5T B optimal?
  Same question as before!
• Are there E-Flow performance issues in the
  forward direction? Are the end EMCals far enough
  from the IP?

23
HCal Assumptions and Questions

• HCal assumed to be 4 l thick, with 34 layers 2 cm
  thick alternating with 1 cm gaps. Is 4 l right?
  What about layer thickness?
• Need large area of inexpensive detectors. e.g.
  high reliability RPCs (Have they been invented
  yet???) Probably glass RPC. GEMs??? Other???
  Note that digital analog is a non-issue for us.
  
• HCal radiator non-magnetic metal probably
  stainless. Is iron the right material?
• Hcal thickness important cost driver, even though
  HCal cost small. And where is it relative to
  coil?

24
HCal Location Comparison
2l 4l 6l
80 M 60 M 40 M 20 M 0 M
0 M -10 M -20 M -30 M
Scale Relative to 4 l Inside!!
2l 4l 6l
Hcal inside coil
HCAL outside coil
25
Coil and Iron

• Solenoid field is 5T 3 times the field from
  detector coils that have been used in the
  detectors. - CMS will be 4T.
• Coil concept based on CMS 4T design. 5 layers of
  superconductor about 72 x 22 mm, with pure
  aluminum stabilizer and aluminum alloy structure.
  The aluminum alloy structural strips are beefed
  up relative to CMS.
• Coil Dr about 85 cm
• Stored energy about 1.5 GJ (for Tracker Cone
  design, R_Trkr1.25m, cosqbarrel0.8). (TESLA is
  about 2.4 GJ) Aleph is largest existing
  coil at 130 MJ
• Is 5T right? And is it buildable? We need a
  pre-conceptual design!

Br
Bz
26
Flux Return/Muon Tracker

• Flux return designed to return the flux!
  Saturation field assumed to be 1.8 T, perhaps
  optimistic.
• Iron made of 5 cm slabs with 1.5 cm gaps for
  detectors, again reliable RPCs.
• Does the flux really need to be returned?
• Are 5 cm slabs ok?

27
More Cost trade-offs
Caveat Based on Si _at_ 6/cm2, W _at_ 100/Kg.
Delta , Fixed BR25x1.252

• vs R_Trkr1.8M/cm

28
Not Worried about yet

• Small angle systems
• Vibration Control
• Crossing angle correctors
• And others!
• All are important, and must be done right but
  unlikely to be design drivers in the class with
  E-Flow, B, Rcal.

29
Timing Analysis!

• 2015 Begin Operation ???
• 6 years construction - 2009
• 3 years serious RD - 2006
• 2 years conceptual design, including first
  critical rounds of testbeam work!!! - 2004
  now??
• We need answers to these questions to get to a
  credible conceptual design!
• We need answers to these questions to compare
  performance with the TPC based detectors!