proposal for uk involvement in calice

13 May 2002 UK CALICE Involvement 1

Proposal for UK involvement in CALICE

Paul Dauncey Imperial College

for the CALICE-UK groups


The UK people• 19 names, 5 institutes:

• Birmingham; C.M.Hawkes, N.K.Watson• Cambridge; C.G.Ainsley, M.A.Thomson, D.R.Ward• Imperial; D.A.Bowerman, W.Cameron, P.D.Dauncey, D.R.Price, O.Zorba• UCL; J.M.Butterworth, D.J.Miller, M.Postranecky, M.Warren• Manchester; R.J.Barlow, I.P.Duerdoth, N.M.Malden, D.Mercer, R.J.Thompson


A future linear collider

A future e+e– linear collider (LC) with:• High centre-of-mass energy; 500 – 1000 GeV• High luminosity; 3 – 10 x 1034 cm-2 s-1

is regarded as a high priority for the future of HEP.It is strongly supported worldwide:• EFCA; July 2001.• HEPAP/Snowmass; September 2001.• ACFA; September 2001.as well as in the UK:• Blair report; September 2001.and the technical feasibility was demonstrated by:• TESLA TDR; March 2001.


Physics at a linear collider

The earliest date for a LC to start would be 2012, so it has to be seen in the context of the LHC:• Higgs; mass will be known (if it exists).• Existence of SUSY; some particles identified if so.• Top quark mass; known to 1 - 2 GeV

The physics programme at a LC would complement that from the LHC (as LEP did after UA1/2) with precision measurements:• Fundamental quantities; e.g. Higgs and top mass.• Distinguish models; e.g. details of SUSY spectrum.


Particular highlights of a LC physics programme include:• Higgs; mass, width, fermion and gauge boson couplings, spin and parity, self-coupling.• SUSY; masses, couplings, mixing parameters, charged Higgs, separation of close-lying states.• Strong Symmetry Breaking; if no Higgs, study WLWL

and ZLZL scattering with W+W– and ZZ final states.• Top; mass to 0.2 GeV with a threshold scan.

LC physics programme could take around 10 years

Physics at a LC (2)

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Calorimetry at a LC

Most states of interest result in quarks and hence hadronic jets; combining these to give masses needs:• Angles; straightforward to measure accurately.• Energies; much more complicated.

LEP experience showed jet energies are best measured using “energy flow” algorithms:• Explicit association of tracks and clusters.• Prevents double counting of track/cluster energies.• Needs a “tracking calorimeter” with fine granularity.• Intrinsic calorimeter energy resolution is secondary for jets (but still needed for e/)Aleph achieved E/E = 60%/E in the central region.


TESLA TDR Si-W ECAL

TESLA TDR specified a silicon-tungsten (Si-W) sampling electromagnetic calorimeter:• 40 layers, between 0.4 and 1.2X0

(radiation lengths).• 24X0 total thickness.• 32 million channels.


Si-W properties

Tungsten has:• Small Moliere radius; ~ 9 mm; gives narrow showers and so reduces overlaps. The effective Moliere radius depends also on gap and pixel sizes.• Short radiation length; X0 ~ 3.5 mm; depth of ECAL can be kept small ~ 20 cm.• Small radiation/interaction length; good longitudinal separation of EM and hadronic showers.Silicon diodes also have good properties:• Dimensions; gaps and pixels can be kept small• Signals; reasonable size and simple to use


TDR ECAL issues

TDR tried to specify a “perfect” physics ECAL:• No amplification inside calorimeter volume

• No cooling pipes needed• Keep gaps small

• Si pixel sizes 1cm x 1cm• Matched to Moliere radius• Large number of channels to calibrate

• Electronics space restricted

• Requires significant electronics integration; analogue, digital and optical


TDR ECAL cost

The main figure of (de)merit is the cost…ECAL total cost of 133 Meuros ~ 90 Mpounds:• Silicon wafers; 70% of the cost:

• Effectively only depends on the total area, i.e. number of layers.• Pixel size is almost irrelevant to cost.

• Coil size; ~2 Meuros per extra cm:• Gap size directly impacts size (multiplied by a factor 40)

Cost/performance optimisation is needed:• Complex, multi-parameter space.


TDR performance

For hadronic jets, TDR calorimeters give E/E = 33%/E with further improvement possible from better algorithms.• For Z or W to two jets, this givesZ/W ~ Z/W

• DistinguishesW+W– and ZZ final states• Photons haveE/E = 1%+10%/E• Higgs gives m ~ 2 GeV

E/E = 60%/E E/E = 30%/E

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What needs to be known

How does jet resolution degrade with:• Number of layers; obvious cost factor for Si wafers• Pad size; determines number of channels and hence electronics cost• Number of dead channels; wafer yield is major cost factor for Si wafers• Inter-layer gaps; can cooling pipes be inserted? Can electronics be inside the ECAL?• Resolution/calibration; how good does it need to be and how will it be measured?

These require an accurate hadronic simulation to answer:• For a possible LC start in 2012, need answers by 2005


The CALICE collaborationFormed to study issues of calorimetry for a LC. Currently 96 physicists, 17 institutes, 7 countries:• Spokesperson; J.-C. Brient, LPNHE - Ecole Polytechnique• Steering Board chair; R.-D. Heuer, Hamburg/DESY.

Studying both ECAL and HCAL, as energy flow requires integrated approach:• ECAL; Si-W option UK interest• HCAL; tile scintillator or “digital” RPCs

Two separate efforts:• “Physics prototype”; beam test UK interest• “Technical prototype”; mechanical TDR structure


Physics prototypeBeam test of ECAL and both HCAL options. ECAL;• Total 30 layers, 24X0;

• 10 x 0.4X0

• 10 x 0.8X0

• 10 x 1.2X0

• Total 9720 channels;• 3x3 wafers/layer• 6x6 channels/wafer

• Active volume;• 18 x 18 x 18 cm3

Scheduled for early 2004


UK proposal

We propose to work in two areas:• Readout and DAQ; for the physics prototype. We would provide the readout electronics for the ECAL. As the tile HCAL might be able to use the same boards, we propose to supply those also. We would also provide the DAQ for the whole system.• Simulation studies; on the development of energy flow algorithms and the impact of the calorimeter design. In addition, we would work on the ECAL cost/performance optimisation.

These both clearly lead to analysis of the beam test data


Proposed readout systemShort timescale, so aim for simplicity and robustness, not high performance or any major technical development.

All in VME; readout boards directly connected to wafer/VFE PCBs, trigger board to distribute trigger in crate


Readout board

• Reads out 6 PCBs; total of 15 readout boards.• 18 channels from each VFE chip digitised by 16-bit ADC; 648 total per board.• DACs for calibration pulse to VFE inputs.• FPGA for board control, VFE and VME interfaces.• Board reads 1296 bytes per event; 19 kBytes total for ECAL.


Trigger and test boards

The trigger board handles trigger to readout boards:• Distributes trigger to readout boards via J2 backplane.• Vetos further triggers until readout complete.• Possibly distributes triggers to HCAL readout.

In addition, a test board is needed:• Connects to readout board through PCB cable.• Supplies all VFE output to readout board, checks all VFE input from readout board.• Conceptually an “inverted” readout board with swapped DACs ADCs; similar implementation.


Data acquisition

Needs to readout whole physics prototype, not just ECAL.Data volumes:• ECAL; 9720 channels, ~ 19 kBytes.• Tile HCAL; around 1200 channels, ~ 2 kBytes.• Digital HCAL; around 400k channels, ~50 kBytes.

VME maximum limit will be around 1 kHz; aim for 100 Hz.• Around 107 to 108 events expected.• One to two months data taking.• Total data volume of order 1 Tbyte.


Simulation studies

Simulation studies form an integral part of this work:• Develop energy flow algorithms based on both calorimeters and the inner tracking detectors.• CALICE simulation uses GEANT4; need to verify both the electromagnetic and hadronic interaction descriptions.• Investigate proposed changes to the calorimeter structure or readout and their effect on energy flow resolution.• Optimise the ECAL performance within a more realistic cost envelope; check effects of reducing the number of silicon layers, resolution, dead channels, etc.


Milestones

The end point is fixed; a beam test early in 2004. The schedule to get to this is:• System specification;

• Complete; end June 2002• Readout board;

• Prototype design complete; end December 2002• Prototype fabrication complete; end February 2003• Prototype tests complete; end June 2003• Production design complete; end July 2003• Production fabrication complete; end September 2003• Production tests complete; end December 2003


Milestones (2)

• Test board;• Design complete; end February 2003• Fabrication complete; end April 2003

• Trigger board;• Design complete; end August 2003• Fabrication complete; end October 2003• Tests complete; end December 2003

All prototyping completed within FY02/03.All production completed within FY03/04.


Equipment request

The estimated cost of the equipment is as follows:• NRE; total = £2k• Readout boards; £2800 x 22 boards = £62k• Trigger boards*; £1200 x 3 boards = £4k• Test board; £2900 x 1 board = £3k• Cables*; £30 x 100 cables = £3k• PC and disk; £4k PC, £8k disk = £12k• VME interfaces; £4k PCI/VME, £3k extender = £7k• VME crates; £5k x 2 crates = £10kThe total is £103k, of which £23k would be spent in FY02/03 and the remaining £80k in FY03/04.(*Cost depends on external factors and is less certain)


Engineering effort

The estimated engineering effort needed is as follows:• Readout boards; 18 months• Trigger boards; 6 months• Test board; 6 months• Layout and fabrication; 4 monthsThe total is 34 months, of which 17 months would be needed in FY02/03 and the remaining 17 months in FY03/04. The University groups can provide 18 months of this; we request the rest from RAL TD:• Board design; 12 months, 6 months in each FY• Layout and fabrication; 4 months, 2 months in each FY


SummaryExcellent calorimetry is vital to the physics programme of a future linear collider. Algorithms and simulation both need work to be able to design the calorimeters needed.

Within the ECAL, there are many interesting problems to be solved. The baseline TESLA TDR solution may not be optimal and can probably be made cheaper.

The UK has a critical mass of bodies to get involved; it• Has made itself known to the CALICE collaboration• Has carved out a role in the short term• Is keeping options open for the longer term• Needs funding to proceed further

proposal for uk involvement in calice

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