PID for super Belle (design consideration)

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PID for super Belle (design consideration)

• Barrel (TOP counter)
• Possible configuration
• Geometry
• Endcap (Aerogel RICH)
• Photo detector options
• Barrel-Endcap

• K. Inami (Nagoya-u)

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Super B detector

• PID (p/K) detectors
• Inside current calorimeter
• Use less material and locate near calorimeter
• ? TOP and Aerogel RICH counters
• both Cherenkov ring imaging detectors

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TOP counter

• Quartz 255cmL x 40cmW x 2cmT
• Focus mirror at 47.8deg.
• to reduce chromatic dispersion
• Multi-anode (GaAsP) MCP-PMT
• Linear array (5mm pitch), Good time resolution
  (lt40ps)
• ? Measure Cherenkov ring image with timing
  information

MCP-PMT
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TOP counter

• Measure PositionTime
• Compact detector!

Simulation 2GeV/c, q90 deg.
Linear array PMT (5mm) Time resolution s40ps
2m
200ps
K p

• Different opening angle for the same momentum
• ? Different propagation length( propagation
  time)
• TOF from IP works additively.

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Chromatic dispersion
Variation of propagation velocity depending on
the wavelength of Cherenkov photons

• Due to wavelength spread of detected photons,
  propagation time becomes worse.
• Longer propagation length
• ? Improve ring image difference
• But, decrease time resolution.
• ? Optimal propagation length.

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Possible configuration

• Detector type
• 3-readout type
• Optimized propagation length
• Simple configuration ? less technical issue
• Simple ring image ? easy reconstruction
• Focusing type
• Correct chromaticity
• 2/3 PMTs
• Cost
• Small dead space
• Easy to replace PMTs because of no middle PMT
• Complicated ring image
• Need noble reconstruction method
• May need more simulation study to check
  robustness

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Possible configuration

• Photo-cathode of MCP-PMT
• Multi-alkali
• Almost established production
• Enough lifetime
• GaAsP
• Better efficiency at longer wavelength
• Need more production RD and lifetime test
• Multi-alkali without Al protection layer on MCP
  (option)
• Better efficiency (x1.6)
• Almost established production, but need some
  modification to improve lifetime (3-layer MCP,
  operation with lower gain, etc.)

GaAsP MCP-PMT
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Performance

• 3-readout type GaAsP photo-cathode
• gt400nm filter, Correction Eff.35

3.5s K/p for 4 GeV/c, q70?
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Performance

• Focusing type GaAsP photo-cathode
• gt400nm filter, Correction Eff.35

4.2s K/p for 4 GeV/c, q70?
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Performance

• Focusing type Multi-alkali
• gt350nm filter, Correction Eff.60

Because of complicated ring image
3.5s K/p for 3 GeV/c, q70?
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TOP configuration summary
option K/pi separation performance at 70 deg, 4GeV/c critical issues
3 readout multi-alkali 2.8 sigma (Make prototype)
3 readout GaAsP 3.5 sigma PMT production PMT lifetime
Focusing multi-alkali 2.5 sigma ? 4.0 sigma if improved eff. PMT lifetime
Focusing GaAsP 4.2 sigma PMT production PMT lifetime

• Focusing type can reduce the dead space and
  remove middle PMT.

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Geometry

• Similar with BaBar DIRC
• Narrow space for support structure
• Only 16mm between quartz bar
• Gaps in f ? 10 dead space
• 1cm weak region from bar edge

18 counters in r-f
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Geometry (2)

• Possible overlapped layout
• Need 50cm-width quartz bars (? 40cm-width)
• R1080 of inner radius (? R1150 for previous)
• Difficulty for
• support structure
• Complicated space
• Need simulation study
• Requirement from physics
• Check S/N with B?rg/Kg etc.
• PID performance
• confirm dead space
• Effect to outer detector

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Aerogel RICH

• Radiator
• Aerogel (n1.05)
• Multiple radiator option
• Set suitable radiator index
• By stacking the radiators,
• Increase Nphoton
• without deteriorating ring image
• Photon detector
• HAPD, MCP-PMT, MPPC etc.
• Single photon detection
• 400nm Cherenkov photon
• Operational under
• 1.5T magnetic field
• High hit rate

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Photon detector option

• HAPD
• Good result from test bench with ASIC readout
• Stability? Need more production RD
• MCP-PMT
• Good TTS for TOF information
• lt20ps TOF resolution
• Good ability for low momentum PID
• Need lifetime estimation
• SiPM/MPPC
• Good stability, Enough gain and TTS
• Need large effective area or light guide to make
  5x5mm2 anode
• Need gated readout because of high dark count
  (ltMHz)

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Barrel - Endcap

• Need to minimize dead space
• TOP needs PMT region at bar end.
• ? We can cover with aerogel radiator.
• To detect Cherenkov light
• emitted to outside,
• we should set mirrors at
• Aerogel RICH outer cylinder.
• Simulation study to estimate
• separation power
• Some RD with mirrors

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Summary

• Photon detector is still main issue for
  designing.
• GaAsP/Multi-alkali photo-cathode MCP-PMT for TOP
• HAPD, MCP-PMT and MPPC with light guide for
  Aerogel RICH
• TOP configuration
• Focusing type GaAsP photo-cathode MCP-PMT
  (gt4.2s)
• Option Multi-alkali with efficiency improvement
• Geometry of TOP bars
• 10 dead space along f
• Overlapped TOP geometry ? Check requirements from
  physics
• Barrel Endcap
• Need design study of outer boundary of Aerogel
  RICH
• Mirror to correct the out-going Cherenkov photons

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Focusing TOP

• Use l dependence of Cherenkov angle to correct
  chromaticity
• Angle information ? y position
• Reconstruct Ring image from 3D information (time,
  x and y).
• Dqc1.2mrad over sensitive l range
• ? Dy20mm (quartz thickness)
• We can measure l dependence and obtain good
  separation even with narrow mirror and readout
  plane, because of long propagation length.

Dqc1.2mrad
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Geometry

• Possible layout with overlap
• Need 50cm-width quartz bar