Mark ThomsonLCUK Meeting, Oxford CALICE STATUS Mark Thomson University of Cambridge Overview UK Hardware UK Simulation UK Reconstruction Conclusions

Mark Thomson LCUK Meeting, Oxford

CALICE STATUSMark Thomson

University of Cambridge

Overview UK Hardware UK Simulation UK Reconstruction Conclusions

For the CALICE-UK groups: Birmingham, Cambridge, Imperial, Manchester, RAL, UCL


Calorimetry at a Future LCMuch LC physics depends on reconstructing

invariant masses from jets in hadronic final statesKinematic fits don’t help – Beamstrahlung, ISRJet energy resolution is of vital importance

62 % charged particles : 27 % : 10 % KL,n : 2 %

The Energy Flow/Particle Flow Method

The energy in a jet is:

• Reconstruct momenta of individual particles avoiding double counting

Charged particles in tracking chambersPhotons in the ECALNeutral hadrons in the HCAL (and possibly ECAL)

need to separate energy deposits from different particles


Calorimeter Requirements

ECAL

granularity more important than energy resolution, i.e. $$$

e

KL,n

Separation of energy deposits from

individual particles

Discrimination between EM and

hadronic showers

• small X0 and RMoliere : compact showers

• small X0/had

• high lateral granularity : O(RMoliere)

• longitudanal segmentationContainment of EM showers in ECAL

Energy flow drives calorimeter design:


Calorimeter Concept ECAL and HCAL inside coil Better performance – but impacts cost

ECAL: silicon-tungsten (SiW) calorimeter:• Tungsten : X0 /had = 1/25, RMoliere ~ 9mm (gaps between Tungsten increase effective RMoliere)• Lateral segmentation: 1cm2 matched to RMoliere

• Longitudinal segmentation: 40 layers (24 X0, 0.9had)

HCAL: digital vs. analogue (major open question):• Tile HCAL (Analogue readout) Steel/Scintillator sandwich Lower lateral segmentation 5x5 cm2 (motivated by cost)• Digital HCAL High lateral segmentation 1x1 cm2 but digital readout RPCs, GEMS…


CALICE Collaboration

Study calorimetry for a future linear colliderProposed high-granularity ECAL/HCAL $$$ need to fully justify/optimize the calorimetry for FLCTestbeam studies of ECAL and HCAL ECAL studies of Si-W calorimeter HCAL studies of both analogue and digital options

GOALS:Demonstrate technical feasibility of ECALValidate MC simulation (particularly hadronic showers ) vital for optimisation of final design Study digital vs analogue HCAL

PEOPLE: 177 people, 27 institutes (including DESY) 23 UK collaborators !

AIMS


UK ContributionReadout and DAQ for test beam prototype Provide readout electronics for the ECAL (Possibly use UK boards for some HCAL options) DAQ for entire system

Simulation studies ECAL cost/performance optimisation Impact of hadronic/electromagnetic interaction modelling on design. Comparisons of Geant4/Geant3/Fluka

Reconstruction/Energy Flow Started work towards ECAL/HCAL reconstruction Ultimate goal – UK Energy flow algorithm

Luminosity spectrum from Bhabha acolinearity (UCL)


HCAL

ECAL1m

Beam monitor

DAQ

Test Beam and Prototype

Moveable table

Combined ECAL & HCAL Engineering Run late 2004 in e- beam at DESY (ECAL only) Physics Run in 2005 p/ beam at FNAL (TBC) HCAL: 38 layers Fe Insert combinations of:

“digital” pads (350k, 1x1cm2 pads)

GEM RPC

“analogue” tiles (8k, 5x5cm2)

Scintillator tiles


Prototype ECAL

3x10 layers, Si-W 0.4X0, 0.8X0, 1.2X0

Each layer 3x3 wafers Each wafer 6x6 pads 9720 channels total

External Readout (VFE) Wafers Si/W/Si Sandwich

Carbon Fibre/Tungsten


Readout OverviewCALICE ECAL has 9720 channelsEach gives analogue signal, 14-bit dynamic rangeVery-front-end (VFE) ASIC (Orsay) multiplexes 18 channels to

one output lineVFE-PCB handles up to 12 VFEs (216 channels)Cables from VFE-PCBs go directly to UK VME readout boards,

called Calice ECAL Readout Cards (CERCs)Based heavily on CMS tracker readout

• Rutherford Laboratory– Adam Baird, Rob Halsall, Ed Freeman

• Imperial College London– Osman Zorba, Paul Dauncey

• University College London– Matt Warren, Martin Postranecky

• Manchester University– Dave Mercer


•Prototype design completed last summer•Two prototype boards fabricated last year

•Arrived on November 21 at Rutherford Laboratory

CERC status

•Currently under stand-alone tests in the UK•Aim to test with a

VFE-PCB in the UK very soon

•Move UK hardware to Paris (Ecole Polytechnique) for cosmic tests with fully populated VFE-PCB with Si wafers in Feburary

Front End FPGAs

Back End FPGA


Outstanding IssuesFinal path for data has several complex steps

FE digitises ADC data for each triggerAutomatically transferred to 8MByte memoryMemory read from VME when bandwidth available

Needs data transfer, memory control and VME interfaceBE FPGA firmware not yet functionalMemory components delayed in delivery; not yet mounted on

CERCsAiming for end of March for all this to be working !

Backup for VFE testsImplement simple RS232 interface from PC to BE and hence to

FEsRS232 reads FIFO one word at a time directly to PC8MByte memories bypassed, must read each event before next

triggerRate is slow ~1Hz for events; sufficient for cosmics


ScheduleVFE tests in Paris in February

Essential test of prototypes before moving to production

Possible AHCAL test in AprilNeed more information on what is required; number of

channels, interface specification for VFE-PCB equivalent,…

Finalise redesign by end MarchRe-layout/fabricate 9 production CERCs in April-May

Simple fixes for the few known problems may be possible

If so, maybe no need to re-layout; save a month

Only have components for nine boards; need to know early if more wanted for HCAL

Will need non-UK funds for HCAL readout

Full ECAL system tests from July onwardsOn schedule for DESY ECAL test beam in Oct/Nov


Test Beam Requirements

Use MC studies to study what data would be most useful in validating MC models (David Ward)

e.g. Compare samples of

5 GeV + in Geant3 (histohisto) and Geant4 (points)

Significant differences seen at the level of 104 events

HCAL shows greatest discrepancies

5 GeV +

What Data ? Proton/pion/muon ?How much data ?


Differences depend on Energy

1 GeV + 50 GeV +

Therefore scan over energies


Protons vs Pions 5 GeV p 5 GeV +

Need to understand beam ! i.e. pion/proton ratioFind protons/neutrons v. similar (at least in MC)Greater differences for Scintillator HCAL vs. RPC


Test Beam : Conclusions

1% precision suggests >104 events per particle type and energy.

Would like energies from 1-80 GeV (~10-15 energy points?).

Pions and protons desirable (Čerenkov needed). +Electrons (+ muons?) for calibration.

Need to understand beam Both RPC and Scintillator HCAL needed. Position scan – aim for 106 events/energy point? Also some data at 30-45o incidence.


Study of hadronic models (G Mavromanolakis, N. Watson)

Compare: (G Mavromanolakis)• Geant 3 with Gheisha• Geant 3 / Gheisha (SLAC

version)• Geant 3 / Fluka• Geant 3 / Fluka / Micap (used

for n < 20 MeV)

• Geant 4 / Mokka

Also Studying:Variations of Geant 3/Geant 4

cutoffs (G Mavromanolakis)Geant 4 FLUKA (N.Watson) - Geant 3 version deprecated - Geant 4 implementation extremely interesting - tricky to get working, but making excellent progress


Calorimeter Reconstruction High granularity calorimeter – very different from

previous detectors

`Tracking calorimeter’

• Requires new approach to reconstruction

• Already a lot of good work on powerful energy flow algorithms

• Still room for new ideas/ approaches

• Current codes : inflexible

UK Effort just starting (Chris Ainsley)• Important for future analysis and `energy flow’ studies/detector optimisation


ECAL Clustering Aim – to produce a flexible algorithm, not tied to

specific geometry/MC program.

• Algorithm needs to cope with tracks and clusters

• Sum hits within cell; apply threshold of ⅓ MIP

• Form clusters in layer 1 of ECAL.

• Associate each hit in layer 2 with nearest hit in layer 1 within cone of angle . If none, initiate new cluster.

• Track onwards layer by layer through ECAL and HCAL, looking back up to 2 layers to find nearest neighbour, if any.


Example Events 15 GeV - 15 GeV e-

(Reconstructed clusters are colour-coded, black = highest energy cluster)

Handles CLUSTERS and TRACKS


Some more difficult examples 15 GeV 15 GeV -

Separates nearby ECAL clusters

So far things look good, but this is just the first stage


Conclusions CALICE ECAL prototype progressing well - test beam before end of 2004 ! Confident that UK Electronics/DAQ will be ready Work on Digitization simulation starting

(D.Bowerman, C.Fry) UK contributing significantly to understanding FNAL

test beam requirements On-going studies of hadronic models UK reconstruction effort starting - important for analysis of test beam data - important for optimisation of ECAL design Next 2 years are going to be very interesting UK groups well placed to participate in analysis of test

beam data



RPC vs. Scintillator HCAL Scintillator RPC


Neutrons vs Protons

5 GeV p 5 GeV n


Eight Front End (FE) FPGAs control all signals to front end electronics via front panel input connectors

Back End (BE) FPGA gathers and buffers all event data from FE and provides interface to VME

Trigger logic in BE for timing and backplane distribution; only active in one board

Each input is one full or two half-full VFE-PCBs; need 45 inputs = 6 CERCs

Based on CMS tracker readout (FED)

CERC overview


Readout DetailsBased on CMS silicon tracker readout (FED)

Will “borrow” a lot of firmware from themUnfortunately not yet as well-developed as hoped

Dual 16-bit ADCs and 16-bit DACDAC fed back for internal as well as front end calibrationADC 500kHz; takes ~80ms to read and digitise event data from

VFE-PCBNo data reduction in readout board

ECAL event size: 3.5 kBytes per board, 20 kBytes total per eventOn-board buffer memory; 8 MBytes

No buffering available in ECAL front end; receive data for every trigger

Memory allows up to ~2k event buffer on readout board during beam spill

VME readout speed ~20 MBytes/s; several seconds readout after spill

Large amount of unused I/O from BE FPGA to backplaneWill implement trigger logic and control/readout interface to VME

in BE

Documents

Mark ThomsonLCUK Meeting, Oxford CALICE STATUS Mark Thomson University of Cambridge Overview UK Hardware UK Simulation UK Reconstruction Conclusions