31 October 01Plans for ECAL Involvement Plans for UK involvement in ECAL (CALICE) Paul Dauncey Imperial College z Status of (non-UK) ECAL work z What is

31 October 01 Plans for ECAL Involvement

Plans for UK involvement in ECAL (CALICE)

Paul Dauncey Imperial College

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


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!


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


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


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


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


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


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?


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?


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


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


Readout electronics

TDR puts all electronics outside active volume• Still very small space ~ few cm

Requires significant integration: analogue, digital and optical


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


Short term aimsMain 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


UK ContributionWe 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


SummaryWithin 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?

Documents

31 October 01Plans for ECAL Involvement Plans for UK involvement in ECAL (CALICE) Paul Dauncey Imperial College z Status of (non-UK) ECAL work z What is