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Tianchi Zhao University of Washington

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.

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Tianchi Zhao University of Washington

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  1. 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

  2. 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

  3. 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

  4. 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

  5. Options for EM Calorimeter Section • Any other EM calorimeter considered for ILC • 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

  6. 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 (?)

  7. 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

  8. Cherenkov Light Yield of 1 Charged Particles Chrenkov light yield: 200 – 300 photons/cm Plastic scintillator light yield ~ 10,000 photons/cm Forward Isotropic • Lead glass was popular calorimeter material in LEP experiments • Cast or extruded lead glass has the same light yield as cut/polished crystals

  9. Cherenkov Plate Readout by MPPC or SiPM Cherenkov photon  Photoelectrons Target: Combined efficiency =η1×η2× η3 ×η4  >1% • η1:probability of a photon hitting the core of a WLS fiber • η2 :conversion efficiency of WLS fiber • η3 : light trapping efficiency in WLS fiber • η4 : MPPC/SiPM quantum efficiency MPPC or SiPM WLS fiber 2 cm Cherenkov Radiator

  10. Signals from a   1 Charged Particle • Cherenkov light yield: N0 = 400 ’s in 2cm radiator • Light collection efficiency by WLS fiber: η1 ~ 50% • WLS fiber efficiency: η2 ~ 80% • Assume η3 ~ 10% with mirror at far end of fiber • MPPC Q.E.: η4 ~ 40 % (100 pixel device may be sufficient) Number of P.E. = N0 x η1 x η2 x η3 x η4 = 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

  11. An Alternative Configuration 5 mm plastic scintillator 20 mm lucite 25 mm steel Basic structure 5 mm uranium First 30 layers Last 10 layers

  12. 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

  13. 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.

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