K2K and JHF near detectors

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NuFact02, July 2002, London
K2K and JHF near detectors
Takaaki Kajita, ICRR, U.Tokyo For the K2K collab.
and JHF-Kamioka WG
JHF
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Outline

• K2K near detector system
• Basic idea for JHF near detectors
• Summary

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K2K experiment _at_KEK
Birds Eye Neutrino Beam Line
Front (Near) Detector
200m
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K2K near detector
300m from the target
(SciFi)
(1Kton)
(MRD)
312 ton (1ev / 20spills)
6 ton
25 ton
Fid. Vol.
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Beam direction? (MRD)
(0.5GeV lt Eµ lt 1.0GeV)
?1mrad
profile center x (cm)
profile x
(1.0GeV lt Eµ lt 2.5GeV)
3-4 mrad. accuracy required.
profile center y (cm)
profile x
June 99 Apr. 01

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Role of the SciFi detector
µ
p
Max osc.
MRD
SciFi
Fraction of non-quasi-elastic events must be
understood well.
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1kton water Cherenkov detector
Predict the Super-Kamiokande flux.
Overall normalization error on Nsk for Nov99
Error ()
KTon 4.4
SK 3.0
Flux 3.7 -3.4
Far/Near 5.6 -7.3
NC/CC 0.2 -0.3
nQE/QE 0.5 -0.8
others 0.7
Total 8.6 -9.7
KTon dominated by fid vol error SK
similar to Kton.
List of uncertainties ? energy scale ? FC event
selection ? Particle ID ? Ring counting ?
Fiducial volume ? Angular resolution ?
Threshold ? Events ? gt 90 degree.
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K2K near detector upgrade
?m2310-3eV2 E?600MeV. Lower
energy ? interactions should be studied.

• Full Active (solid) Scintillator Tracker
• High efficiency for a short (lt4cm) track.
• Detect a proton down to 350 MeV/c.
• PID (p/p) by dE/dx and momentum
• Fine segments (1.32.5300cm ).

Monte Carlo
p
3m
µ
3m
45,000 events _at_31019pot
14,400 channels
1.8m
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JHF near detectors
Second near detector _at_2km from the target
Target
Decay pipe (L130m)
280m
?
First near detector _at_280m from the target
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Required accuracy
JHF-Phase I
JHF-Phase II (with Hyper-K)

• Discovery of non-zero ?13
• Precise measurement of ?23 and ?m .

• CP violation

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Flux prediction _at_far detector
2
5
?Main near detector should be water Ch. ?Near
detector pos. must be gt1.5km.
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Some information on the beam.
Max. osc. (must be predicted accurately)
Number of events /100MeV/yr
Background (must be understood well)
E?(GeV)
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Event rate Far/near ratio
2
6 /100ton/spill _at_280m
_at_280m
2
Not a good place.
1
(ffar / fnear)(Lfar / Lnear)
0
_at_2km
0.1 /100ton/spill _at_2km
OK !
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Distance from target (km)
Water Cherenkov Impossible _at_280m (Total mass gt
100 tons)
0
0
1
2
3
E?(GeV)
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Near detector _at_280m

• Beam profile monitor
• Cannot be water Cherenkov
• Detailed study of neutrino interactions _at_1GeV
• No detailed design.., but could be something
  like

0 deg.
Super-K
10m ?
? This profile is obsolete Just to give the
idea.
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Near detector _at_2km
Muon detector
Water Cherenkov detector
Fine grained scintillater detector
8m
? beam
4m
8m
8m
15.2m
5m
Total mass 1000ton
9.2m f
Fid. Mass 100ton
Details not designed yet
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Stopping point distribution of muons
4m
?
2m
Edge of the fid vol.
Measured by muon detector
Detector surface
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The detector should look like.
Surface building
Scintillator detector
Water Ch.
Muon counter
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Summary

• Multi component K2K near detector system is
  essential to understand the neutrino beam and
  interactions.
• In the JHF-Kamioka neutrino project, the near
  detector system should be similar to the K2K
  system.
• However, in JHF, the distance between the target
  and the near detector should be gt 2km.

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End
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Beam energy stability ? (MRD, 1Kton)
MRD
1Kton
2000 2001
Every month
Eµ (GeV)
Pµ(GeV/c)