Calorimetry @ the

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Calorimetry _at_ the

• - Physics motivation
• - Performance goals
• Design considerations
• for a LC Calorimeter

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Physics at the LC

• Discoveries and precision measurements
• Rare processes
• Limited statistics
• Final states with heavy bosons W, Z, H
• Need to reconstruct their hadronic decay modes
  
• ?multi-jet events
• In general kinematic fits dont help
  (Beamstrahlung, ISR)

500 events
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WW/ZZ separation
Dilution factor vs cut integrated luminosity
equivalent

• No Higgs scenario
• WW scattering violates unitarity at 1.2TeV, or
  new forces show up
• access EWSB mechanism from WW scattering
• analyze ee?WWnn and ee?ZZnn channels
• need to separate ZZ background
• no kinematic fit possible due to the neutrinos

? Smaller dilution factor for a60 is equivalent
to a loss of 40 luminosity
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Jet energy resolution

• Challenge separate W and Z in their hadronic
  decay mode
• Dijet masses in WWnn, ZZnn events (no kinematic
  fit possible)
• ? 40 more lumi is required for same resolution
  if a60

LEP-like detector
LC design goal
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The Higgs boson

• If there is a Higgs
• the main production mechanisms are
• High energy ? WW fusion
• Low energy ? Higgs-strahlung
• In the channel ZH ? ZWW ? 4jets l ?

s/B in ZH ? ZWW ? 4jets l ?
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2
a30 gives 20 better precision or 40 less lumi
required
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The Higgs potential

• Is the Higgs the Higgs?
• Check l M2H/2v2

ee? ZHH ? 6 jets
Nev (1ab-1)

• few tens of events
• reconstruct observable from 3 dijet masses
• ?with LEP-like detector significance lt 3s

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Other requirements
decay of a long lived neutralino in gauge
mediates SUSY braking

• directional resolution ?
• photon impact parameter
• (need e.g. few cm _at_ 20 GeV)
• hermeticity
• SUSY events ? large missing energy
• suppress two photon background with ee lost in
  the beam direction
• lepton identification
• timing

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Calorimetry at a Future LC
?Jet separation and energy resolution are the
key issues for new physics
The energy in a jet is
? Goal ?/E 30/?E
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Particle Flow Method (ideal)
First measure charged particles (62) -momenta
measured with tracking chambers ?/pT 5 X 10-5
pT -merge track to calorimeter
clusters -substitute calorimeter energy with
momentum i.e. for Ejet 100 GeV ? contribution
of 190 MeV to ?/E
The rest of energy in the calorimeter is assigned
to neutral clusters photons (26)
(?/E)ECAL 15-20/?E ? 900 MeV to ?/E neutral
hadrons (10) (?/E)HCAL lt 80/?E ? lt 3
GeV to ?/E ? This method requires extremely high
granularity
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Jet energy resolution (reality)
TESLA TDR
Ideally
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P-flow implications on calorimetry
Traditional Standards Hermeticity Uniformity Comp
ensation Single Particle E measurement Outside
thin magnet (1 T)
P-Flow Modification Hermeticity Optimize
ECAL/HCAL separately Longitudinal
Segmentation Particle shower reconstruction Inside
thick coil (4 T)
Optimized for best single particle E resolution
Optimized for best particle shower
separation/reconstruction
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Imaging calorimeter
ZHH g qqbbbb
red track based
green calorimeter based
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Principle of Calorimetry
Calorimeter detector which degrades the energy
of an incoming particle to the level of
ionizations and excitations which are detected in
some active media (gas, scintillator, crystals,
etc.) Incoming particles shower producing many
low energy charged particles the shower is
characterized by its spatial development in terms
of a quantity track length Track Length (T)
sum of tracks of all charged particles in a
shower Calorimetry works because T ? E (the
energy of the particle)
T EX0/? for a given material ? is called
critical energy 550/Z (MeV)
from U. Amaldi, Fluctuations in Calorimetry
Measurements, Physica Scripta, Vol. 23, 409-424,
1981.
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Sampling Calorimeter
Sampling Calorimeter the degraded energy is
measured in many sampling layers consisting of
an absorber material and an active detector
What causes the measured energy to have a spread?
Digital Calorimeters sampling fluctuations or
fluctuations in the total number of e and e-
tracks crossing the sensitive planes (N) N
E/? X0/x E/?E (?E is the energy lost by a MIP
in 1 layer)
Analog Calorimeters sampling fluctuations
fluctuations in the deposited energy (asymmetric,
Landau distribution) path length fluctuations
(apparent increased thickness of active media)
-gt ideally ?analog gt ?digital
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Readout concept Analog vs Digital
From photon analysis ECAL requires Analog readout
?/mean 16
Analog Readout perfect ? cluster
Non-linear behavior for dense showers
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Readout concept Analog vs. Digital
From hadron analysis HCAL can have either Analog
or Digital readout
S.Magill (ANL)
?/mean 20
Average 43 MeV/hit
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Calorimeter quality

• Calorimeter figure of merit
• B R2calo / (r2Molierr2cell)
• magnetic field limited by mechanical stability
  B2Rcoil lt 60 T2m
• ?separation of energy deposited from individual
  particles
• ?discrimination between EM / hadronic showers

• small X0 and rMoliere compact showers

• high lateral granularity r2cell r2Molier

• small X0/lhad ?

• longitudinal segmentation

?containment of EM showers in ECAL
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The X0 / lI factor
Iron X0/lI 1.8cm/17cm 0.1
Tungsten X0/lI 0.35cm/9.6cm 0.04
Tungsten
Iron
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Comparison with existing detectors
?compare barrel ECAL of various detectors
Experiment H1 ATLAS CMS TESLA
Detector PbLAr PbLAr SiPbW04 SiW
B T 1.2 2 4 4
B R2calo / r2Molier 1.8x103 1.5x103 14x103 178x103
X0/lhad 0.26 0.26 0.04 0.04
Nch/V /m3 45x103/53850 190x103/1001900 620x103/87700 38x106 /37gt1x106
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FLC Calorimeter design

• ECAL silicon-tungsten (SiW) calorimeter
• Analog readout of silicon pads
• Tungsten X0 /lhad 1/25, RMoliere 0.9cm
• Lateral segmentation 1cm RMoliere
• Longitudinal segmentation 40 layers (24 X0)

• HCAL digital vs. analogue (major open question)
• Sampling structure with Steel plates and
• Analog HCAL (Tile HCAL)
• Lower lateral segmentation 5x5 cm2
  (motivated by cost)
• Active material -
  scintillator
• Digital HCAL
• Higher lateral segmentation 1x1 cm2 but
  digital readout
• Active material under study - scintillator
  
• - gas (RPCs, GEM)

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ECAL structure

• high hermeticity
• no dead zones
• All modules are identical

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ECAL Detector Slab
tungsten
Carbone Fiber
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HCAL Analog or Digital?

• low E ?digital better than analogue due to
  suppressed Landau fluctuations
• high E ? analog better than digital
• Possible solution multiple thresholds
  (semi-digital)
• Digital require small pad size 1cm
• ?small scintillator tiles
• ? gas small pad readout

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D-HCAL Scintillator RO
Concept Scintillator thickness 5 mm
Hexagons of 9.4 cm2 area Trade-off
segmentation with readout resolution
? Considering 2 bit readout
( 3 thresholds)
Northern Illinois University
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D-HCAL Gas or Scintillator?
Gas can be used as active material in a sandwich
calorimeter
Shower width ? proportional to density
A.Sokolov (IHEP)

• Advantage of Resistive Plate Chamber RO
• Very low cost and easy to build detector
• Robust detector no ageing effect
• Large signal, high efficiency, low noise rate

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D-HCAL GEM readout
University of Texas at Arlington
Concept Gas volume for ionization GEM
foils for multiplication ? perforated
Pads for signal pick-up
3 mm gas gap
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Gas Electron Multiplier
Very strong electric field in GEM holes Incoming
e- get accelerated and multiplied by multiple
collisions in the gas
From CERN-open-2000-344, A. Sharma
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A-HCAL Prototype _at_ DESY
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A-HCAL Scintillator RO
Tile size 5x5x0.5 cm3
1-loop or curve-diagonal WLS-fiber (Y11) placed
in groove (not glued) Single tiles covered by 3M
reflector
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Test of 3 types of Photo-Detector

• MA-PM 16 channels (Hamamatzu)
• best photo-detector
• cannot be operated in magnetic field
• single tile or cell read out

Only for reference

• Avalanche photo-diode (APD,Hamamatzu
  S8664-55spl)
• different from those used by CERN experiments
• 3x3mm2 low capacity
• gain 200 ?various preamp board tested _at_ DESY
• quantum eff. 75
• cell read out 3 tiles

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Principle of operation

• ADP operated with avalanche
• multiplication 50-500
• ?signal proportional to energy
• deposited
• SiPM operated in Geiger mode
• avalanche multiplication 2106
• - R 400 k? prevents detector
• break down
• Proportionality to energy is lost
• Semi digital device

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Signal to Noise ratio
Pedestal

• Signal to noise ratio of SiPM at room temperature
  compared to APDs and Visible Light Photo
  Detectors in case of MIP signal
• Improvement in SiPM w.r.t. APD due to absence of
  electronics noise
• (no preamplifier needed for SiPM)

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MIP Calibration
PM MIP/sped15 MIP/sMIP4.5
sMIP
MIP
MIP MPV-pedestal
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Shower pattern reconstruction
Lateral shower shape
Longitudinal shower shape
increasing depth ?
MC data
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Energy Resolution
Results obtained at DESY test beam with A-HCAL
prototype

• Very good agreement between PM and SiPM on the
  whole range 1 - 6 GeV
• Low sensitivity to constant term due to limited
  energy range
• MC tuning still in progress
• include more effects
• -beam energy spread
• -steal thickness tolerances

Preliminary

• SiPM
• PM
• MC (SiPM)

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Goal of first Prototype
First working prototype to test the concept of
high granularity tile-calorimeter - light yield
optimisation - tile uniformity - test of novel
photo-detector - MIP calibration - stability
monitoring - MC simulation MiniCal prototype
has been operational since May 2003 at the DESY
test beam 1 6 GeV e It is a collaborative
effort of various institutes HH-university,
DESY, MEPHI, Prague, LPI, ITEP
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Future the physics prototype
VME/
DESY project 1 m3 Tile HCAL prototype 8000
calorimeter tiles equipped with SiPM To be
tested together with the ECAL prototype Both
analogue and digital HCAL options will be tested
HCAL
BEAM
ECAL
Beam monitoring
10 GeV pions
Movable table
? Tail catcher needed for full shower
containment
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Geometry optimization

• Define physical observable for optimization
• ? Shower reconstruction/separation
• Generate two 10 GeV showers initiated by
• p and K0L
• Use track information for p
• Complete shower reconstruction algorithm used
• (see papers from Vasilly Morgunov)
• Test three options of tile size and readout
• scheme
• - 1 layer of 3x3 cm2 tiles
• - 2 layers of 3x3 cm2 tiles
• - 1 layer of 5x5 cm2 tiles
• Compare to ideal particle flow algorithm

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Geometry optimization
Shower separation quality is defined as
the fraction of events in which the neutral
shower is consistent with the energy in the case
of ideal P-flow within 3s. Shower separation
quality versus generated shower distance gives a
good criterion for geometry comparison ? Final
choice 1 layer of 3x3 cm2 tiles in the core
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Monitoring System
Next studies will focus on a reliable monitoring
system for large number of tiles (gt8000 for the
physics prototype) Requirements - low light
yield ( 5-10 ph.e.) pre-amplification is
required ? to monitor SiPM gain ? -
medium light yield ( 25 ph.e 1 MIP) ? to
monitor stability of MIP calibration -
high light yield ( 200-500 ph.e.) ? to
monitor saturation behaviour Options under
investigation - LED system, single or multiple
tile per fiber - Laser system
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An International Effort

• Linear collider detector RD is partially
  organized in (open) proto-collaborations, e.g.
  CALICE
• 164 Physicists, 28 Institutes, 9 Countries 3
  Regions

• CALICE prepares beam test series in 2005-06
• ECAL and HCAL together, different options
• electron test beam periods start end 2004 at DESY
• followed by hadron test beam at ???
  (Protvino/FermiLaB/)

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Conclusion

• The linear collider physics represents a
  formidable challenge for calorimeters
• met by a world-wide RD effort, internationally
  coordinated
• An interesting test beam period is ahead of us,
  to sharpen our views on imaging calorimetry and
  particle flow algorithms
• to further push for overall optimized detector
  concepts