シンチレータストリップを用いた高性能電磁カロリメータの開発（公募研究Ａ１）
研究代表者 川越清以 (神戸大学)
with the GLC calorimeter group(KEK, Kobe, Konan, Niigata, Shinshu, Tsukuba)
9-Mar-2004, 科研費特定領域 第2回研究会 in Tsukuba(Special thanks to Dr. Matsunaga)zIntroduction
zHardware study with test beams
zPhoton sensors
zSimulation study
zFuture planzSummaryIntroductionz Design criteria for LC calorimetergood energy resolution for single
particlesfine transverse/longitudinal granularity
for “particle flow” analysis
hermeticity
operational in strong magnetic fieldz Required performance2-jet mass resolution better than W/Znatural widthOur approach to the designcriteriaz Baseline design :Lead/plastic scintillator
sampling calorimeter for both
ECAL and HCALz Hardware compensation for
excellent hadron energy
resolution and linearity
z Good hermeticity
z Good granularity
z Established technology andreasonable costz According to fast simulation,
this conservative design canfulfill design criteria

Reconstructed W mass fore+e-->W+W- at 400GeV(result of fast simulation inwhich ECAL cell size was10cm)
σ (Mjj) = 2.9GeV

Our previous studies
zStudy on energy resolution and linearity
Test beam measurements at KEK and FNAL ECAL with 4mm-Pb/1mm-Sci :for electrons
HCAL with 8mm-Pb/2mm-Sci /2mm-Acryl :for pionsz Tile/fiber calorimeter with hardware
compensation has been verified to meet ourdesign criteria for energy resolution andlinearity even with current design of granularity
 Detailed simulation study must be doneHCAL studies with test beam(1996-1999)

z Good energy resolution andlinearity thanks tohardware compensation

Fine granularity ECALz Currently studying fine granularity ECAL withPb/Sci sampling technique examine “particle flow” analysis capabilityz Baseline design : tile/fiber ECAL

 4cmx4cmx1mm-Sci + 4mm-thick Pb

z Optional design : strip-array ECAL
 1cmx20cmx2mm-Sci + 4mm-thick Pb

z Shower-max detector with scinti-strips
 Conventional WLS readout
 Directly-attached APD readoutz Require multi-channel photon sensors
operational in magnetic fieldPurposes of test beam studies(1) Tile/fiber ECAL examine uniformity with staggerd WLS layouts(2) Strip-array ECAL

 uniformity measurement for the simulator inputs
 measure energy, position, shower direction
 examine 2-cluster separation and ghost-rejection(3) WLS-readout SHmax
 position resolution
 e/π separation(4) Direct-APD SHmax examine feasibility : S/N for MIP signal
 position resolution

Test beams for new ECAL design
z 2002 Nov.: T517 at KEK (e/µ/π, 1-4 GeV) tile/fiber ECAL, strip-array ECAL, scinti-strip SHmax

z 2003 Sept.: test at DESY (e, 1-6 GeV) scinti-strip SHmax

z 2004 March: T545 at KEK (e/µ/π, 1-4 GeV) tile/fiber ECAL, strip-array ECAL, scinti-strip SHmax
 probably the last opportunity for KEK PS beamline

Setup of T517 test beam measurement

(1) Tile/fiber ECALz Small cell size of 4cm x 4cm,0.7mmφ-WLS
z Effect of small bending radiusof WLS fiber ?
z Non-uniformity (around towerboundary) ?
z Only 2 super layers (2002)z Full-depth, mega-tiles (2004)
z Multi-anode PMTs

WLS fiber configurationz Two types of groove layout to smear non-uniformity

Roundish-square groove layout

Circular groove layout

Non-uniformity measurements
z Better uniformity with alternating layout

Spatial resolutionz Position resolution of 2nd S.L.
σ (x or y) ~ 0.7cm at 4GeV

as a function of beam energy(2) Strip-array ECAL
zFull-depth test module was constructed and tested in 2002
z24 layers (17X0), 6 super-layers
z1 layer = lead plate (4mm-thick) + x-strips + y-strips
z20cm x 1cm x 2mm scinti-strip with 1mmφ-WLS
zMulti-anode PMTs (tentatively for beam test)Energy resolution
Test beam

GEANT3 simulation

w/o photon statistics

If photon statistics is taken into account, beam
test results are consistent with simulation.

Linearityz Linearity : < 3.5%
 < 1% above 2GeV
 deviation at 1GeV :due to material infront of ECAL ?
z In good agreementwith simulation

Spatial resolution
A 4GeV electron event :Fitted to Gaussian

Position resolution
for 4GeV electron

σ =2.0mm
around shower max

Angle measurement
zShower-axis angle is determined bylinear fitting points in the first 5 S.L.
zMean S.L. position in beam direction
is calculated with weighted mean ofenergy deposit obeying shower curveAngle measurement (cont.)z Incident angle : 0 ~ 3degreez Offset due to mis-alignment ?
z Ignoring offset, angles are correctly
measured within errors

Response uniformity
z Response in 1st super layer for 2Gev π and ez Response-sum over strips : uniformity < 5%

2-particle separation / ghost
rejection 2 clusterz For strip-array ECAL, ghost must
be rejected pulse height analysis could help for
rejection

 2-particle separation and ghost
rejection : study in progress
particle ghost
particle

separation in 1dim. (2nd S.L.)
1cm
2cm
3cm

ghost4cm

(3,4) Shower-max detectors
z For tile/fiber ECAL case,position detector at shower
maximum is needed for better position resolution
 better track-cluster matching good e/π separation capability

z Scinti-strip detector is anatural option for our ECAL baseline design : WLS readout
 optional design : directlyattached APD

Readout of scinti-strip
z Strip-size :20cm x 1cm x 1cm
z Conventional readout:
WLS + clear fiber tozMA-PMTs (tested)zHPDs (2004)
z Directly-attached APDs
on scinti-strip (tested)z SiPMs directly on WLS(2004)

SHmax test modules
Scinti-strips with WLS fibers

Scinti-strips with directly
attached APDs

(3) Position resolution of SHmax(WLS read out)
Before S-shape correction

6 GeV electrons(DESY)

correctedxSM(cm)xSM(cm)z XSM : measured
position with
Gaussian fit

z XDC : incident
positiondetermined bydrift chambers

After S-shape correction

xDC(cm)σ = 1.9mm

xDC(cm)σ = 1.7mm
xSM-xDC(cm)xSM-xDC(cm)Position resolution of SHmax(cont.)
Electron incident position is determined with weighted
mean of 5 strips for figures below:

Pb thickness = 24cm
Electron energy (GeV)vs. Pb thickness in front︵ cm︶Position resolution

Position resolution （cm）

vs. electron energy

2GeV e6GeV ePb thickness (mm)

(4) Performance of APD-SHmaxz APD : Hamamatsu S8864-55
 Active area : 5mm x 5mm, gain ~ 50
 Temperature coefficient : ~5%/degree
MIP signal is well
separated from pedestal

corrected

Spatial resolution as a functionof electron energy
Weighted mean
methodADCcountPhoton sensors
z Multi-pixel Hybrid Photodiode (HPD) DEP-HPD used for CMS-HCAL We have tested Hamamatsu 64 pixels
HAPD (Dr. Suyama) Gain = 6 x 104 (good) Commercially not yet available

z Electron-bombarded CCD (EBCCD)
 Suitable for fiber readout
 〜400 fibers/device possible
 Low gain (< 1000), but Sensitivity to single-photon
 Slow read out, no timing informationz Will be tested with SHmax in 2004
test beamPhoton sensors (cont.)z SiPM Micro-APD cells operated inGeiger mode
 1ch/device, compact, cheap(a few $/device) High gain (~106), but
significant noise rate Can be directly attached toWLS fiber ~10 SiPM from DESY to betested in 2004 beam test
 HPK is developing a similar
photon sensor

Simulation studies
z Implemented geometry for both options ofECAL into GEANT3-based full simulatorz Detailed studies, such as shower clustering and trackcluster matching, are still under studyz Will move to GEANT4-based simulationz Basic implementation is done; need more refinementz Behind schedule due to insufficient man power
and need to do beam test before KEK-PS
shutdown

Future planzFinalize ECAL hardware study in 2004
zAccelerate simulation studies
Full simulation in GEANT4 frameworkJet clustering

zContinue to study photon sensors
SiPM, HPD, EBCCD….

zInternational collaboration : photonsensors, scinti. production, …
zEngineering study

Summary
zFine granularity ECAL based onlead/scintillator sampling is being
studied :established technology, reasonable costenergy resolution, linearity, hermeticity
a series of beam tests is being carried out:
tile/fiber ECAL, strip-array ECAL, SHmax
Final beam test starts soon.
new photon sensors are being tested
simulation studies are in progress