analog vs. digital hadron calorimetry for the...
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Analog vs. DigitalAnalog vs. DigitalHadronHadron CalorimetryCalorimetry
for the ILCfor the ILCDhiman Chakraborty
for the NIU/NICADD ILC detector group
International Linear ColliderLarge Detector Meeting
LLR, Paris, January 13-15, 2005
ILC LD meeting, 14-01-2005
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IntroductionIntroduction
We consider a hadronic calorimeter with a few thresholds (1-3).Compare gas and scintillator as live media:
Single particle energy resolution,Shower width,Clustering.
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Geometries ConsideredGeometries Considered
Scint HCal
Steel 20mmPolystyrene 5mm
Gas Geom1
Steel 20mm
Gas 5mm
Gas Geom2
G10
Glass 1mm
Gas 1mm
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Number of cells hit by Number of cells hit by ππ++s of s of 2, 5, 10, 20, 30, 50 GeV2, 5, 10, 20, 30, 50 GeV
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ππ++ energy resolution as function of energy resolution as function of energy for different (linear) cell sizesenergy for different (linear) cell sizes
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EEnergy resolution for 10 GeV nergy resolution for 10 GeV ππ++ss
σ/E=0.183 σ/N=0.166
9cm2 cells
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EEnergy resolution for 50 GeV nergy resolution for 50 GeV ππ++ss
σ/E=0.101 σ/N=0.153
9cm2 cells
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Nhit Nhit correlations for different correlations for different cell energy thresholdscell energy thresholds
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Nhit correlations for different cell Nhit correlations for different cell energy thresholdsenergy thresholds
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Nhit correlations for different cell Nhit correlations for different cell energy thresholdsenergy thresholds
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Alternatively,Alternatively,
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CompensationCompensation
Cell counting has its own version of the compensation problem (in scintillators).With multiple threshold this can be overcome by weighting cells differently (according to the threshold they passed).In MC, 3 thresholds seem to be adequate
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After semiAfter semi--digital treatmentdigital treatment
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Energy resolution:Energy resolution: 5050 GeV GeV ππ++ss
σ/E=0.101 σ/E=0.092
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Energy resolution: 10 GeV Energy resolution: 10 GeV ππ++ss
σ/E=0.183 σ/N=0.164
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ππ++ energy resolution vs. energyenergy resolution vs. energy
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Time of flightTime of flight
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ToF dependenceToF dependence
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CrossCross--talktalk(10% of cell E leaks equally to 4 neighbors)
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Nhit vs. fraction of Nhit vs. fraction of ππ++ E in cells with E>10 MIP:E in cells with E>10 MIP:1cm1cm x 1cm x 1cm scintillator cellsscintillator cells
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Nhit vs. fraction of Nhit vs. fraction of ππ++ E in cells with E>10 MIP:E in cells with E>10 MIP:GasGas vs. scintillatorvs. scintillator
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ππ++ energy resolution vs. energyenergy resolution vs. energyM
ultip
le th
resh
olds
not
use
d
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NonNon--linearitylinearityNhit/GeV varies with energy.This will introduce additional pressure on the “constant” term.For scintillator the non-linearity can be effectively removed by “semi-digital” treatment.
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Density of hitsDensity of hits
Need a hierarchy in the absence of an energy measurementLocal density of hits is an obvious candidate. A simple-minded density variable:
di = Σ (1/Rij),where Rij is the angular distance between cells i & j.
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Position resolutionPosition resolutionM
easu
red
rela
tive
to th
e en
ergy
wei
ghte
d re
solu
tions
unweighted
Density weightedEnergy weighted
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Density vs. Density vs. EnergyEnergy
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WidthWidthFind centroid {Σwixi/Σwi}‘width’ = sqrt(ΣwiR2
i/Σwi)Three weights were used:
Unweighted (wi=1)
Energy weighted (wi=Ei)
Density weighted (wi=nearest-neighbor occupancy in a 5x5 window in lyrs k-1,k,k+1)
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Distance to Distance to farthestfarthest cellcell
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Density Density of farthestof farthest cellcell
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Distance to farthest cellDistance to farthest cell
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Density of farthest cellDensity of farthest cell
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BackscatterBackscatter
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Shower Shower widthwidth for 10GeVfor 10GeV ππ±±
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Shower width for 50GeVShower width for 50GeV ππ±±
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π± angular widthrms shown as bars
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ππ±± angular width: energy weightedangular width: energy weighted
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ππ±± angular width: density weightedangular width: density weighted
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CommentsCommentsThere is no clear cut case either way at the moment; detailed studies of assessing impact needed.Will look at cluster separability next.Need to evaluate this in the global context of calorimeter performance.
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ClusteringClusteringClustering based on local densityworks well.It is an alternative to track-seeded clustering.Can be used in the ECal and HCal.Full PFlow implementation givesencouraging results.
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10 GeV10 GeV ππ0 0 →→ γγγγD
ensi
ty w
eigh
ted
θ−φ
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ΣΣ++ →→ ppππ0 0 →→ ppγγγγ
p
π0
Den
sity
wei
ghte
dθ−
φ
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SummarySummaryLarge parameter space in the nbit-segmentation-medium plane for hadron calorimetry. Optimization through cost-benefit analysis?Scintillator and Gas-based ‘digital’ HCalsbehave differently.Need to simulate detector effects (noise, x-talk, non-linearities, etc.)Need verification in test-beam data.More studies underway.