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? Plans for ECAL Involvement

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! Plans for ECAL Involvement

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 Plans for ECAL Involvement

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 Plans for ECAL Involvement

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 Plans for ECAL Involvement

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 Plans for ECAL Involvement

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 Plans for ECAL Involvement

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? Plans for ECAL Involvement

9. Silicon quality • Silicon diode pads (reasonably) standard technology • Little to gain in signal size etc. from R&D • Degradation of resolution acceptable with dead diodes • Gain factor 2 in yield = factor 2 in cost? Plans for ECAL Involvement

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 Plans for ECAL Involvement

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 Plans for ECAL Involvement

12. Readout electronics • TDR puts all electronics outside active volume • Still very small space ~ few cm • Requires significant integration: analogue, digital and optical Plans for ECAL Involvement

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 Plans for ECAL Involvement

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 Plans for ECAL Involvement

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 Plans for ECAL Involvement

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? Plans for ECAL Involvement