P1259082933OZdTI

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Concept of an Active Absorber Calorimeter A
Summary of LCRD 2006 Proposal A Calorimeter Based
on Scintillator and Cherenkov Radiator Plates
Readout by SiPMs Tianchi Zhao University of
Washington Adam Para Fermilab

Tianchi Zhao University of Washington
March 12, 2006, LCWS06 Bangalore, India
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Energy Compensation
Hadron energy Eh is given by
Eh Compensated hadron energy Esc Energy
measured by plastic scintillators Ech Energy
measured by cherenkov radiators
Reference 1. Compensating hadron calorimeters
with Cerenkov light Winn, D.R.
Worstell, W.A. , IEEE Trans. NS Vol 36 (1989) 334
2. Hadron Detection with a Dual-Readout
Calorimeter N. Akchurina et al., NIM A
537 (2005) 537-561 3. Cherenkov Compensated
Calorimetry, Yasar Onel et al., 2004 LCRD
Proposal
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Basic Idea of Active Absorber Calorimeter In a
sampling calorimeter based on active detector
(scintillator) absorber layers, partially
replace absorber plates by cherenkov radiator
and read out both scintillation light and
cherenkov light.

• Thin plastic scintillator plates
• Measure energy of both hadron and EM
  components of hadron showers as in a standard
  sampling calorimeter

• Thick Cherenkov radiator plates
• Measure mostly energies of EM components in
  hadron showers in an active absorber calorimeter

• Both readout by WLS fiber and SiPM/MPPC

Heavy structural layer
Cherenkov radiator
Plastic scintillator
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Configuration Example Consider a 40 layer
arrangement
Last 10 layers
First 30 layers
5 mm plastic scintillator
20 mm lead glass
25 mm steel
1.3 X0
5 mm steel
Material Layers ?T (cm) Layer ? Thickness (cm) No. of ?T
Plastic scintillator 40 80 40 ? 0.5 20 0.25
Lead glass 30 30 30 ? 2 60 2
Iron 30 16.8 30 ? 0.5 15 0.89
Iron 10 16.8 10 ? 2.5 25 1.49
TOTAL 40 120 4.63
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Options for EM Calorimeter Section

1. Any other EM calorimeter considered for ILC
2. A segmented active absorber calorimeter with dual
   energy readout

Example
3 mm scintillator
15 mm PbF2

• Good EM energy
• resolution
• Maintaining energy
• compensation

2 mm tungsten
20 layers
3 mm scintillator
15 mm PbF2
2 mm tungsten
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Transverse Segmetation

• Need Monte Carlo simulation to optimize the
  choice of
• segmentation for
• - EM section
• - Front part of hadron section
• - Back part of hadron section
• Minimum size of plates mainly limited cost
  considerations
• ? 3 cm 3 cm (?)

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Cherenkov Light Readout by WLS Fiber
Bicron 408 6 x 6 x 30 mm3
Lead glass SF57 10 x 10 x 40 mm3

• Groove along 40 mm length
• White paper wrapped
• ?1 mm BCF-91AWSL fiber
• One end open
• XP1911 PMT
• (Average Q.E. 13 for BCF-91A )

Number of p.e. measured by using cosmic ray
muons Lead glass 2.4 ? 0.5 p.e. Bicron
408 27 ? 4 p.e.
Ralph Dollan, 2004 Thesis
P.E. yield of lead glass is about 5 of plastic
scintillator
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Cherenkov Light Yield of ??1 Charged Particles
Plastic scintillator light yield 10,000
photons/cm
Chrenkov light yield 200 300 photons/cm
Forward
Isotropic
Cherenkov Radiator Density X0 (cm) ? (cm) Index of refraction Absorption Edge (nm)
SF2 lead glass 3.85 2.76 38 1.65 330
SF6 lead glass 5.2 1.7 30 1.81 360
SF57 lead glass 5.5 1.5 28 1.85 370
PbF2 crystal 7.8 0.93 20 1.82 250
UVT acrylic 1 40 80 1.5 250

• Lead glass was popular calorimeter material in
  LEP experiments
• Cast or extruded lead glass has the same light
  yield as cut/polished crystals

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Cherenkov Plate Readout by MPPC or SiPM
Cherenkov photon ? Photoelectrons
Target Combined efficiency ?1 ?2 ?3 ?4
? gt1

• ?1 probability of a photon hitting the core of
  a WLS fiber
• ?2 conversion efficiency of WLS fiber
• ?3 light trapping efficiency in WLS fiber
• ?4 MPPC/SiPM quantum efficiency

MPPC or SiPM
WLS fiber
2 cm
Cherenkov Radiator
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Signals from a ? ? 1 Charged Particle

• Cherenkov light yield N0 400 ?s in 2cm
  radiator
• Light collection efficiency by WLS fiber ?1
  50
• WLS fiber efficiency ?2 80
• Assume ?3 10 with mirror at far end of fiber
• MPPC Q.E. ?4 40 (100 pixel device may be
  sufficient)

Number of P.E. N0 x ?1 x ?2 x ?3 x ?4 400 x
1.6 6.4
MPPC
Mirror
WLS fiber

Should be able to make reasonable measurements
for high energy EM showers
WLS fiber high efficiency for blue light emits
green/yellow light to match MPPS
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An Alternative Configuration
5 mm plastic scintillator
20 mm lucite
25 mm steel
Basic structure
5 mm uranium
Last 10 layers
First 30 layers
Material Layers ?T (cm) Layer ? Thickness (cm) No. of ?T
Plastic scintillator 40 80 40 ? 0.5 20 0.25
UVT Lucite 30 70.3 30 ? 2 60 0.85
Uranium 30 10.5 30 ? 0.5 15 1.43
Iron 10 16.8 10 ? 2.5 25 1.49
TOTAL 40 30 120 4.02
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Potential Advantages

• Energy compensation for hadron showers on event
  by event basis as demonstrated by the DREAM
  Project, but allowing for fine transverse and
  longitudinal segmentation
• Performance should be better than the dual r
  eadout calorimeter of Dream project since
  cherenkov radiator in our implementation is 2/3
  of total volume!!
• Energy resolution should be better than a
  calorimeter based only on scintillator plates and
  should achieve the required jet energy
  resolution
• Tighter spatial spread of hadron showers recorded
  by Cherenkov radiator may help correctly
  assigning energy clusters in HCal to tracks that
  produced them, therefore, improving the results
  of PFA.
• Very flexible design options for material choices
  and segmentations

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Disadvantages

• Significant cost increase compared to HCal that
  uses plastic scintillator plates only
• Density of calorimeter is reduced compared to a
  design that uses passive absorber only. Using a
  heavy metal such as uranium or tungsten may solve
  this problem.