Offaxis Neutrino Monitor of T2K

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Off-axis Neutrino Monitor of T2K

• K. Hiraide (Kyoto Univ.)
• NBI2005 _at_ FNAL
• July 7-11, 2005

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1. Introduction

• Goal of T2K phase-I
• Precise measurement of ?? disappearance
• ?(sin2 2?23)0.01
• ?(?m232)10-4 eV2
• Search for ?e appearance
• sin2 2?13gt0.008 _at_?m23x10-3 eV2
• Assumed 5x1021POT for 5years
• (off-axis 2.5degree beam)

w/o oscillation
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1-1. Systematic uncertainties

• ?? disappearance

• ?e appearance

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1-2. Off-axis Near Detector

• Role of Off-axis Near Detector
• To reduce systematic errors
• Neutrino flux spectrum measurement at a near
  site
• ?? flux spectrum
• Intrinsic ?e contamination
• Neutrino interaction study for background
  estimation
• CC-1? (?? disappearance)
• NC-1?0 (?e appearance)

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1-3. Off-axis detector position
Neutrino spectrum at various off-axis position
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2. Conceptual design
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2-1. Scinti. Tracker TPC

• Measurement of ? spectrum
• Detailed study of ? interaction
• Scinti. Tracker
• Neutrino interaction target
• 0.06 event/ton/spill
• K2K-SciBar type detector
• ( active water target)
• TPC
• Momentum measurement w/ 0.2T
• (especially ?, p, ??)

?
2.5m
2.5m
TPC
TPC
0.3m
Scinti. Tracker
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2-1. Scinti. Tracker TPC (contd)

• Expected of interactions
• Assuming 2 Scinti. Trackers (2.5mx2.5mx0.3m)
• Fiducial mass 2tons
• Total interaction 340,000 events/year
• CC-QE 120,000 events/year
• CC-1? 65,000 events/year

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2-1. Scinti. Tracker TPC (contd)
Muon acceptance as a function of muon momentum is
studied.
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2-2. Pi0 Detector (POD)

• Measurement of backgrounds for
• ?e appearance (NC-1?0, beam ?e)
• Pi0 Detector
• Scinti. Tracker absorber (Pb)
• Total detector mass 12tons
• Surrounded by ECAL

NC-1?0 12,000 int./ton/year ?e CC 2,500
int./ton/year
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3. Detector RD status

• Photo sensors for FGD, POD
• Requirements
• Operate in a magnetic field of 0.2T
• a few tens of thousands of channels
• Candidate
• Avalanche Photo Diode
• Si PM
• Micro-channel plate MAPMT

Si PM
Now RD is going on
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3. Detector RD (contd)
APD board

• Avalanche Photo Diode (APD)
• High quantum efficiency
• Achieved S/N18.5 _at_ -20oC
• Large temp. dependence of gain

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3. Detector RD (contd)

• Si PM
• Photon counting device
• Noise rate MHz (thr0.5p.e.)

HV42.2V
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2
4
1
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HV41.7V
0
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4. Summary

• Function of off-axis Neutrino monitor
• To measure neutrino flux spectrum at a near
  site
• To study neutrino interaction
• Off-axis detector is essential to reduce
  systematic errors in oscillation analysis
• Conceptual design has been almost finished.
• Detector RD is going on.

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Backup slides
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Off-axis detector position
Kinematical point of view Neutrinos come from
decay volume, not from the target
Z position of pion decay in the decay volume
Mean decay position 46m from the target
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Acceptance of p and ??
Protons from CC peak Pp 400 MeV/c
Charged pions from CC-1? peak P? 200 MeV/c
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Momentum resolution using TPC