K2K and JHF near detectors
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Transcript of K2K and JHF near detectors
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NuFact02, July 2002, London
Takaaki Kajita, ICRR, U.Tokyo
For the K2K collab. and JHF-Kamioka WG
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• K2K near detector system
• Basic idea for JHF near detectors
• Summary
Outline
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Bird’s Eye Neutrino Beam Line
200m
Front (Near) Detector
K2K experiment @KEK
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K2K near detector
flux anddirection
312 ton (1ev / 20spills)
6 ton 25 tonFid. Vol.:
(MRD)
(SciFi) (1Kton)
300m from the target
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Beam direction? (MRD)
profile x
profile x
prof
ile
cent
er x
(cm
)pr
ofil
e ce
nter
y (
cm)
June 99 Apr. 01
1mrad
(0.5GeV < Eμ < 1.0GeV)
(1.0GeV < Eμ < 2.5GeV) ±3-4 mrad. accuracy required.
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Role of the SciFi detector
p
μ
SciFi
MRDMax osc.
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 errorSK: similar to Kton.
List of uncertainties:
⇒ energy scale
⇒ FC event selection
⇒ Particle ID
⇒ Ring counting
⇒ Fiducial volume
⇒ Angular resolution
⇒ Threshold
⇒ Events θ > 90 degree.
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K2K near detector upgrade
Full Active (solid) Scintillator Tracker»High efficiency for a short (<4cm) track.»Detect a proton down to 350 MeV/c.»PID (p/π) by dE/dx and momentum »Fine segments (1.3×2.5×300cm ).
14,400 channels
Monte Carlo
μ
p
3m
3m
1.8m
Δm2=3×10-3eV2 Eν=600MeV. Lower energy ν interactions should be studied.
45,000 events
@3×1019pot
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JHF near detectors
280m
First near detector @280m from the target
Target
Second near detector @~ 2km from the target
Decay pipe (L=130m)
ν
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Required accuracy
• Discovery of non-zero θ13
• Precise measurement of θ2
3 and Δm .
• CP violation
JHF-Phase I JHF-Phase II (with Hyper-K)
2
5% 2%
★Main near detector should be water Ch.
★Near detector pos. must be >1.5km.
Flux prediction @far detector
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Some information on the beam….N
umbe
r of
eve
nts
/100
MeV
/yr
Eν(GeV)
Max. osc. (must be predicted accurately)
Background (must be understood well)
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Event rate & Far/near ratio
Distance from target (km)
6 /100ton/spill @280m
0.1 /100ton/spill @2km
Water Cherenkov : Impossible @280m (Total mass > 100 tons)
(φfa
r / φ
near
)×(L
far /
Lnea
r)2
2
1
1
0
0
@280m
@2km
Not a good place….
OK !
0 1 2 3 Eν(GeV)
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Near detector @280m • Beam profile monitor• Cannot be water Cherenkov• Detailed study of neutrino interactions @1GeV• No detailed design….., but could be something lik
e:• ・・・・
10m ?
0 deg.Super-K
※ This profile is obsolete… Just to give the idea….
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Near detector @2km
Details : not designed yet
9.2m φ
15.2m
8m
4 mTotal mass : 1000tonFid. Mass :
100ton
ν beam
Fine grained scintillater detector
5m
8m
8m
Water Cherenkov detector
Muon detector
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Stopping point distribution of muons
ν
Edge of the fid vol.
2m
4m
Detector surface
Measured by muon detector
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The detector should look like….
Water Ch.
Scintillator detector
Muon counter
Surface building
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Summary • Multi component K2K near detector system is es
sential 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 > 2km.
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End
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Beam energy stability ? (MRD, 1Kton)
Everymonth
Eμ (GeV)
MRD 1Kton
2000
2001
Pμ(GeV/c)