critical questions for sid

J. Brau - ACFA Workshop, Taipei - Critical Questions November 9, 2004 1

Critical Questions for SiDCritical Questions for SiD

A Configuration has been proposedA Configuration has been proposedfor the Silicon Detector.for the Silicon Detector.

This serves as a starting point, andThis serves as a starting point, andsuggests the Critical Questions.suggests the Critical Questions.

Effort must now systematically exploreEffort must now systematically exploreoptimization.optimization.

Based on “Critical Questions for SiD,” Based on “Critical Questions for SiD,” J. Brau, M. Breidenbach, J. Jaros, H. Weerts, Aug 23, 2003J. Brau, M. Breidenbach, J. Jaros, H. Weerts, Aug 23, 2003

(It is assumed this list is incomplete)(It is assumed this list is incomplete)


LC Detector RequirementsLC Detector Requirements

Any design must be guided by these goals:Any design must be guided by these goals:

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 separating bunch-crossings to suppress overlapping of events.


Architecture argumentsArchitecture arguments

Silicon is expensive, so limit area by limiting radiusSilicon is expensive, so limit area by limiting radius

Get back BRGet back BR22 by pushing B (~5T) by pushing B (~5T)

This argument may be weak, considering quantitative cost trade-This argument may be weak, considering quantitative cost trade-offs. (see plots)offs. (see plots)

Maintain tracking resolution by using silicon stripsMaintain tracking resolution by using silicon strips

Buy safety margin for VXD with the 5T B-field.Buy safety margin for VXD with the 5T B-field.

Keep (?) track finding by using 5 VXD space points to determine track Keep (?) track finding by using 5 VXD space points to determine track

tracker measures sagitta.


Cost Trade-offsCost Trade-offs

Cost Partial R_Trkr

0.0

20.0

40.0

60.0

80.0

100.0

120.0

140.0

0.5 0.75 1 1.25 1.5

R_Trkr (m)

Del

ta M

$

$ vs R_Trkr$ vs R_Trkr

~1.7M$/cm~1.7M$/cm Delta $, Fixed BRDelta $, Fixed BR22=5x1.25=5x1.2522

Cost Partial, Fixed BR^2

-5

0

5

10

15

20

25

30

0 1 2 3 4 5 6

B

Del

ta M

$

1.25

1.35

1.45

1.55

1.65

1.75

1.85

Linear

Power

Radius


AssumptionsAssumptions

Energy flow calorimetry is essential for good jet resolution We need to demonstrate this, and to determine rational major detector

parameters that optimize it. Detector cost is constrained.

This assumption will not be buttressed by simulation, but is considered reasonable by most.

The energy flow demonstration is a simulation and reconstruction strategy issue, as are most of these questions.

However, there are a few specific hardware developments that are crucial to determining “rational major detector parameters”.


TrackingTracking

Tracking for any modern experiment should be conceived as an Tracking for any modern experiment should be conceived as an integrated system, combined optimization of:integrated system, combined optimization of: the inner tracking (vertex detection) the central tracking the forward tracking the integration of the high granularity EM Calorimeter

Pixelated vertex detectors are capable of track reconstruction on their Pixelated vertex detectors are capable of track reconstruction on their own, as was demonstrated by the 307 Mpixel CCD vertex detector of own, as was demonstrated by the 307 Mpixel CCD vertex detector of SLD, and are being developed for the linear colliderSLD, and are being developed for the linear collider

Track reconstruction in the vertex detector impacts the role of the Track reconstruction in the vertex detector impacts the role of the central and forward tracking systemcentral and forward tracking system


Silicon TrackingSilicon Tracking

• Superb spacepoint precision allows linear collider tracking measurement goals to be achieved in a compact tracking volume

• Compact tracker makes the calorimeter smaller and therefore cheaper, permitting more aggressive technical choices (assuming cost constraint)

• Robust to spurious, intermittent backgrounds (esp. beam loss) extrapolated from SLC experience

• linear collider is not storage ring


EM

Neutral Hadrons

Charged Hadrons

CalorimetryCalorimetry

Current paradigm: Particle/Energy Current paradigm: Particle/Energy FlowFlow (unproven) (unproven)

Jet resolution goal is 30%/E In jet measurements, use the

excellent resolution of tracker, which measures bulk of the energy in a jet

Particles in JetParticles in Jet Fraction of Visible Fraction of Visible EnergyEnergy

DetectorDetector Resolution Resolution

Charged ~65% Tracker < 0.005% pT

negligible

Photons ~25% ECAL ~ 15% / E

Neutral Hadrons ~10% ECAL + HCAL ~ 60% / E

~ 20% / E

Headroom for confusion


Energy/Particle Flow CalorimetryEnergy/Particle Flow Calorimetry

Follow charged tracks into calorimeter and associate hadronic showers

Identify EM clusters not associated with charged tracks (gammas)

Remaining showers will be the neutral hadrons


Calorimeter QuestionsCalorimeter Questions

For a fixed detector technology, bigger appears to be better. There is general agreement that the numerator of an energy flow figure of merit is BR2.

R is the outer radius of the tracker or the inner radius of the EMCal, probably different by about a cm. If the cost of the calorimeter can be reduced without affecting performance, then BR2 can be

increased. Therefore, primary questions are

1. Can the number of layers of Si in the EMCal (currently 30) be reduced?

2. Do we need 30 radiation lengths? Is 25 or 20 enough?

3. Would a tungsten based HCal with 2X0 thick W ease the EMCal

requirements?


EM CalorimetryEM Calorimetry

Physics with isolated electron and gamma Physics with isolated electron and gamma energy measurements require ~10-15% / energy measurements require ~10-15% / E E 1% 1%

Particle/Energy Flow requires fine grained EM Particle/Energy Flow requires fine grained EM calorimeter to separate neutral EM clusters calorimeter to separate neutral EM clusters from charged tracks entering the calorimeterfrom charged tracks entering the calorimeter

Small Moliere radius Tungsten

Small sampling gaps – so not to spoil RM

Separation of charged tracks from jet core helps Maximize BR2

Natural technology choice – Si/W calorimeters Good success using Si/W for Luminosity monitors at SLD, OPAL, ALEPH Oregon/SLAC/BNL CALICE

Alternatives – Tile-Fiber (challenge to achieve required granularity)Scintillator/Silicon HybridShaslikScintillator Strip

materialmaterial RRMM

IronIron 18.4 mm 18.4 mm

LeadLead 16.5 mm16.5 mm

TungstenTungsten 9.5 mm9.5 mm

UraniumUranium 10.2 mm10.2 mm


Energy Flow IssuesEnergy Flow Issues

Using the latest version of the parametric detector calculator, increasing the tracker radius (from 1.25 m) at fixed B=5T costs about $2.1M/cm.

If BR2 is held fixed at 7.8 Tm2 , then increasing the tracker radius (from 1.25 m) costs about $0.6M/cm.

Note that the baseline design of R =1.25 m and B=5T is a cost minimum if B=5T is considered a maximal field.

So assuming an EMCal with gaps of 1 mm and pixels small compared to the Moliere radius, and sampling often in depth, then:

4. Are the EMCal assumptions above realizable (Physical prototype required)?

5. Is BR2 =7.8 sufficient for the physics benchmark processes?6. Is the improvement expected from increasing R at fixed BR2

justified by the improvement in physics benchmark performance? Why would this improve things ?

7. Can a reasonable energy flow figure of merit beyond BR2 be demonstrated by simulation and reconstruction by early 2005? This should be analogous to understanding the performance variation with B, R, and the calorimeter

properties. It is likely that calorimeter means both EMCal and HCal. Are there issues for the z position of the forward calorimeters.


Silicon/Tungsten EM CalorimeterSilicon/Tungsten EM Calorimeter

SLAC/Oregon/BNL Conceptual design for a dense, fine

grained silicon tungsten calorimeter well underway

First silicon detector prototypes are in hand

Testing and electronics design well underway

Test bump bonding electronics to detectors by end of ’04/early ‘05

Test Beam in ’05/’06


Silicon/Tungsten EM Calorimeter (2)Silicon/Tungsten EM Calorimeter (2)

Pads ~5 mm to match Moliere radius Each six inch wafer read out by one chip < 1% crosstalk Electronics design Single MIP tagging (S/N ~ 7) Timing < 5 nsec/layer Dynamically switchable feedback capacitor

scheme (D. Freytag) achieves required dynamic range: 0.1-2500 MIPs

Passive cooling – conduction in W to edgeAngle

subtended by RM

GAP


Hadron CalorimeterHadron Calorimeter

The baseline assumption is that the HCal is inside the coil, and that it is 4 thick (nominally 34 layers of stainless 20 mm thick with 10 mm gaps).

8. Is this HCal configuration sufficient for the benchmark physics processes?

a. Is this the “right” radiator? How about tungsten?

b. How about more sampling, and is 4 sufficient?

c. The gaps are expensive because they drive out the coil radius. Could they be reduced?

d. 1 to 2 cm square pixels have been assumed. Is this right, particularly if the HCal density is increased?

e. Can thin, cheap, reliable, good resolution detectors be made?

(Physical Prototype required)

(Note that Si is out of the question!!)


Digital Hadron CalorimetryDigital Hadron Calorimetry

1 m1 m33 prototype planned to test prototype planned to test conceptconcept

Lateral readout segmentation: 1 cm2

Longitudinal readout segmentation: layer-by-layer

Gas Electron Multipliers (GEMs) and Resistive Plate Chambers (RPCs) being evaluated

ObjectivesObjectives Validate RPC approach (technique and physics) Validate concept of the electronic readout Measure hadronic showers with unprecedented

resolution Validate MC simulation of hadronic showers Compare with results from Analog HCAL

Argonne National LaboratoryArgonne National Laboratory

Boston UniversityBoston University

University of ChicagoUniversity of Chicago

FermilabFermilab

University of Texas at ArlingtonUniversity of Texas at Arlington


Superconducting SolenoidSuperconducting Solenoid

The superconducting solenoid is large, with more than a GJ of stored energy.

There are concerns that the hoop stress in a 5T, Rcoil=2.6 m might be excessive.

In addition, the coil is a major cost driver, and it thus affects directly what BR2 might be within the cost constraints.

9. Are there serious technical problems with a (thick) solenoid of these nominal parameters? Does the addition of

serpentine correction coils for a crossing angle introduce horrible problems?

10. What is a rational cost parameterization for coils of this scale?



The barrel tracking and momentum measurement are baselined as 5 layers of pixellated vertex detector followed by 5 layers of Si strip detectors (in ~10 cm segments) going to 1.25 m. The momentum resolution for found tracks seems excellent.

11. Does it need to become more complicated?

12. Develop a baseline for the Forward direction.

13. Does this system find tracks well? What about machine and physics backgrounds?

14. Are there issues regarding K0’s and Λ’s i.e. can they be detected efficiently ?

15. Demonstrate (if true) the need to minimize tracker material to minimize multiple scattering.



With superb position resolution, compact tracker is possible which achieves the linear collider tracking resolution goals

Compact tracker makes the calorimeter smaller and therefore cheaper, permitting more aggressive technical choices (assuming cost constraint)

Linear Collider backgrounds (esp. beam loss) extrapolated from SLC experience also motivate the study of silicon tracking detector, SiD

Silicon tracking layer thickness

determines low momentum

performance

3rd dimension may be achieved

with segmented silicon strips,

or silicon drift detectors

(1.5% / layer)

(TPC)


Central Tracking (Silicon)Central Tracking (Silicon)

Optimizing the Optimizing the ConfigurationConfiguration

R. Partridge

Cooper, Demarteau, Hrycyk

support

H. Park


Silicon Tracking w/ Calorimeter AssistSilicon Tracking w/ Calorimeter Assist

V0 tracks reconstructed from ECAL stubs

Primary tracks started with VXD reconstr.

E. von Toerne


Other Important QuestionsOther Important Questions

There are many other important questions that must be studied, but still do not seem to drive the basic design or challenge the fundamental strategy of SiD. For illustration, some of these questions are:

1. What is a rational technology and a more detailed design for the VXD?

2. What is the technology for the muon trackings? Should it be the same as the HCal?

3. What is a design for the very forward calorimetry?


Very Forward InstrumentationVery Forward Instrumentation

• Hermiticity depends on excellent coverage in the forward region, Hermiticity depends on excellent coverage in the forward region, and forward system plays several rolesand forward system plays several roles maximum hermiticity precision luminosity shield tracking volume monitor beamstrahlung

• High radiation levels must be handledHigh radiation levels must be handled• 10 MGy/year in very forward detectors


Machine Detector InterfaceMachine Detector Interface

A critical area of detector R&D which must be optimized is where A critical area of detector R&D which must be optimized is where the detector meets the colliderthe detector meets the collider Preserve optimal hermiticity Preserve good measurements Control backgrounds Quad stabilization

20 mr crossing angle, silicon detector


SummarySummary

A systematic investigation of the Silicon Detector is needed soon. An initial list of Critical Questions has been constructed. What are the additional Critical Questions which should be added to the

high priority list?


Collider ConstraintsCollider Constraints

Linear Collider Detector R&D has Linear Collider Detector R&D has had to consider two different sets had to consider two different sets of collider constraints: X-Band of collider constraints: X-Band RF and Superconducting RF RF and Superconducting RF designsdesigns

With the linear collider technology With the linear collider technology selection, the detector efforts can selection, the detector efforts can concentrate on one set of concentrate on one set of parametersparameters

The ILC creates requirements similar The ILC creates requirements similar to those of the TESLA designto those of the TESLA design

X-BandX-Band

GLC/NLCGLC/NLC

SuperRF SuperRF

TESLATESLA

#bunch/train#bunch/train 192192 28202820

#train/sec#train/sec 150/120150/120 5 5

bunch spacingbunch spacing 1.4 nsec1.4 nsec 337 nsec337 nsec

bunches/secbunches/sec 28800/2304028800/23040 1410014100

length of trainlength of train 269 nsec269 nsec 950 950 secsec

train spacingtrain spacing 6.6/8.3 msec6.6/8.3 msec 199 msec199 msec

crossing anglecrossing angle 7-20 mrad7-20 mrad 0-20 mrad0-20 mrad


Inner Tracking/Vertex DetectionInner Tracking/Vertex Detection

Detector RequirementsDetector Requirements Excellent spacepoint precision ( < 4 microns ) Superb impact parameter resolution ( 5µm 10µm/(p sin3/2) ) Transparency ( ~0.1% X0 per layer ) Track reconstruction ( find tracks in VXD alone )

Concepts under Development for Linear ColliderConcepts under Development for Linear Collider Charge-Coupled Devices (CCDs)

demonstrated in large system at SLD Monolithic Active Pixels – CMOS (MAPs) DEpleted P-channel Field Effect Transistor (DEPFET) Silicon on Insulator (SoI) Image Sensor with In-Situ Storage (ISIS) HAPS (Hybrid Pixel Sensors)


Inner Tracking/Vertex Detection (CCDs)Inner Tracking/Vertex Detection (CCDs)

IssuesIssues Readout speed and timing Material budget Power consumption Radiation hardness

R&DR&D Column Parallel Readout ISIS Radiation Damage Studies

SLD VXD3

307 Mpixels5 MHz 96 channels0.4% X0 / layer~15 watts @ 190 K

3.9 m point res.av. - 2 yrs and 307 Mpxl


Column Parallel CCDColumn Parallel CCD

SLD Vertex Detector designed to read out 800 kpixels/channel at 10 MHz, operated at 5 MHz => readout time = 200 msec/ch

Linear Collider demands 250 nsec readout for Superconducting RF time structure

Solution: Column Parallel Readout LCFI (Bristol, Glasgow, Lancaster, Liverpool, Oxford, RAL)

(Whereas SLD used one readout channel for each 400 columns)


Column Parallel CCD (2)Column Parallel CCD (2)

Next Steps for LCFI R&D

Bump bonded assemblies Radiation effects on fast CCDs High frequency clocking Detector scale CCDs w/ASIC & cluster finding logic; design

underway – production this year

In-situ Storage Devices Resistant to RF interference Reduced clocking requirements


Image Sensor with In-situ Storage (ISIS)Image Sensor with In-situ Storage (ISIS)

EMI is a concern (based on SLC experience) which motivates delayed EMI is a concern (based on SLC experience) which motivates delayed operation of detector for long bunch trains, and consideration of ISISoperation of detector for long bunch trains, and consideration of ISIS

Robust storage of charge in a buried channel during and just following Robust storage of charge in a buried channel during and just following beam passage (required for long bunch trains)beam passage (required for long bunch trains)

Pioneered by W F Kosonocky et al IEEE SSCC 1996, Digest of Technical Papers, 182 T Goji Etoh et al, IEEE ED 50 (2003) 144; runs up to 1 Mfps.

• charge collection to photogate from 20-30 m silicon, as in a conventional CCD

• signal charge shifted into stor. register every 50s, providing required time slicing

• string of signal charges is stored during bunch train in a buried channel, avoiding charge-voltage conversion

• totally noise-free charge storage, ready for readout in 200 ms of calm conditions between trains for COLD LC design

• particles which hit the storage register (~30% area) leave a small ‘direct’ signal (~5% MIP) – negligible or easily corrected


• neutrons induce damage clusters

• low energy electrons create point defects – but high energy electrons create clusters – Y. Sugimoto et al.

• number of effective damage clusters depends on occupation time – some have very long trapping time constants – modelled by K. Stefanov

Radiation Effects in CCDsRadiation Effects in CCDs

N. Sinev et al.Drift of charge over

long distance in CCD makes detector very susceptible to effects of radiation:

•Transfer inefficiency•Surface defects

Traps can be filled

•Expect ~1.5x1011/cm2/yr of ~20 MeV electrons at layer-1•Expect ~109/cm2/yr 1 MeV-equivalent dose

from extracted beamline

Hot pixels

critical questions for sid

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