Plans for UK involvement in ECAL CALICE

1
Plans for UK involvement in ECAL (CALICE)

• Paul Dauncey
• Imperial College

• Status of (non-UK) ECAL work
• What is UK hoping to do?

2
The UK people

• Idea of UK involvement in ECAL raised at RAL
  meeting on 5 June
• Seems to be a lot of interest within the UK
• Now at 15 names 5 institutes
• Birmingham C.Hawkes, S.Hillier, N.Watson
• Cambridge D.Ward, M.Thomson
• Imperial P.Dauncey
• Manchester R.Barlow, I.Duerdoth, N.Malden,
• R.Thompson
• UCL H.Araujo, J.Butterworth, D.Miller,
• M.Postranecky, M.Warren
• Just starting not too late for you to join in!

3
Why an ECAL?
Physics case for ECAL well documented in TDR (and
elsewhere) need good energy-flow
reconstruction (track-cluster matching) to
disentangle jet structure
Aim to distinguish WW from ZZ events
4
Where is the ECAL?

• To get the required performance, both the ECAL
  and HCAL are within the coil
• Cost of coil is very significant factor on size
  of calorimeters

5
Why a tungsten ECAL?

• General agreement that a tungsten calorimeter
  would be best match to the physics requirements.
  Tungsten has
• Small Moliere radius 9 mm gives narrow
• showers and so reduces overlaps
• Short radiation length 3.5 mm depth of ECAL
• can be kept small
• Small radiation/interaction length good
• longitudinal separation of EM and hadronic
• showers

6
Effective Moliere Radius

• Ideal calorimeter has no readout or support!
• Need to add detection layers semi-ideal has
  multiple, very thin, small pixel detection layers
  throughout ECAL volume.
• Figure of merit is effective Moliere radius
  convolution of
• actual Moliere radius
• gap size
• readout pixel size
• Also want to minimise holes and gaps
• Support structure all behind the layers

7
Cost

• The other main figure of (de)merit is the cost!
  TDR gives the ECAL total cost of 133 Meuros 90
  Mpounds
• The silicon pads are 70 of this
• Effectively only depends on the total area
• Pad size is almost irrelevant
• Coil size 2 Meuros per extra cm
• Gap size directly impacts size (multiplied by a
  factor 20-40!)
• Support structure must be small too

8
Mechanical structure

• Tungsten layer structure
• Proposal is to wrap slabs in carbon fibre
  minimal screw hole or other support structure
• Total weight of each eight-fold sector is 14
  tonnes

• Need accurate structure for insertion of
  electronics and minimising gaps between sectors
• Will it support weight within tolerances?

9
Silicon quality

• Silicon diode pads (reasonably) standard
  technology
• Little to gain in signal size etc. from RD
• Degradation of resolution acceptable with dead
  diodes
• Gain factor 2 in yield factor 2 in cost?

10
Number of silicon layers

• Similarly TDR number of layers is 40
• Degradation acceptable for 20
• Factor of 2 in cost?
• Potential savings on total cost of 1/3

11
Front-end electronics

• Gaps should be of order a few mm no water pipes
• Can there really be no cooling in detector
  volume? No cooling probably means no front-end
  electronics

• What temperature would electronics run at?
• Is noise and pickup acceptable with no front-end
  electronics?
• Critical issue integration of mechanics and
  electronics is essential

12
Readout electronics

• TDR puts all electronics outside active volume
• Still very small space few cm
• Requires significant integration analogue,
  digital and optical

13
Politics

• Baseline ECAL program is collaboration of
  French, Russian and Czech groups - CALICE
  Collaboration
• Si-W only Shashlik seems dead
• Coordinated with HCAL effort
• Italian groups studying hybrid (silicon and
  scintillating tile) option mainly to reduce cost
• Ideally would complement each other
• Not ideal e.g. parallel development of Si
  detectors
• Warning this is very TESLA oriented

14
Short term aims

• Main issues are integration can only be studied
  (and solved?) with a prototype
• CALICE proposal to build a test ECAL and HCAL
• Put into test beam in 2003/4 tight timescale
  for us
• Submission to DESY PRC in May this year and
  backup documentation submitted last week
• UK joined CALICE, as this seen to be leading the
  effort
• Signed second PRC document with contingent on
  funding legalese
• UK has observer status in collaboration until
  funding secured

15
UK Contribution

• We are late joining CALICE...
• Many pieces of work already taken up
• Not obvious they are under control
• Main part missing was readout electronics and
  DAQ
• Unlikely to be remotely like final system
• Will also do general simulation and analysis
• Gives us a buy-in for further ECAL work
• Scope of beamtest very ill-defined so far
• Number of channels, ADC speed, trigger rates,
  etc?
• Need to meet up with other groups soon
• When concrete proposal is possible
• Put in costed request to PPRP
• Ideally in first few months of 2002

16
Summary

• Within the ECAL, there are many interesting
  problems to be solved and the baseline solutions
  may not work. The UK has a critical mass of
  bodies to get involved it has
• Made itself known to the CALICE collaboration
• Is carving out a role in the short term
• Keeping options open for the longer term
• Needs PPARC funding costs very uncertain
• Something which needs discussion in the current
  financial climate, should we be very careful to
  coordinate all LC proposals to PPARC? What does
  this mean in practise?