NBI2003@KEK
Nov. 10, 2003

JHFν Near
Neutrino Detectors
T. Nakaya (Kyoto)1

1. Introduction• Precision measurement of νµ→νx.
– Neutrino flux and spectrum (CC-QE).
– Signal purity (CC-QE events) and theestimation of background (Non CC-QE).
oscillation(log)

Nobs/Nexp(w/o oscillation)

1ring FC µ-like∆m2=3×10-3
sin22θ=1.0

Non-QE
Reconstructed Eν (MeV)sin22θ
~3%∆m2
Reconstructed Eν (MeV)2• Search for a rare process: νµ→νe.
~15,000 νµ interactions in 5 years• ~10 BG events from νµ→π0+X.
• ~10 BG events from νe in the beam.

Off axis 2 deg, 5 years– Background estimation. 35

Expected
Signal+BG2
sin 2θ13=0.10
sin22θ23=1.0∆m2=0.003eV230

Total BG

25

BG from νµ+antiνµ20

sin22θ13=0.1∆m23=3×10-3eV215
105000.5

1

1.5

2

2.5 3 3.5 4 4.5
3 5Reconstructed Eν(GeV)

Reconstructed Eν (GeV)Detectors
pπ0m

ν

140m

280m

2 km

• Muon monitors @ ~140m• Near detectors @280m– Neutrino
intensity/direction– Neutrino interaction study• Medium Detector @ ~2km
– Almost same Eν as SK– Water Cherenkov can work

• Far detector @ 295km– Super-K295 km

Spectra at different positions

x 10 3
1800

1.5km

1600

1400

295km

1200

1000

800

600

0.28km

400

200

0

0

0.5

1

1

1.5

2

2

2.5

3

3

3.5

4

4

4.5

5Eν (GeV)

4Eν (GeV)Near neutrino detector @280m

Near Detector Hallν
0 4-0 50 5 -0 6
0 6 -0 7
0 7-0 85

Function of the detectors• On-axis (0 degree)– Beam direction– Beam stability– (Spectrum)?

• Off-axis (2~3 degrees)––––νµ and νe neutrino fluxes and the spectra.
ν interaction study (CC-QE, non-QE, π0, )Kaon Contributions(Nuclear dependence (Carbon v.s. Oxygen))?

The detector design is just starting!!
⇒ The design is not fixed yet, and we have
many options at this stage.
6The Hall

Neutron shield

Side View

16m
SK

SK direction

FGD
MRD

Grid µ profile2°

ν beam5m
PMT

Tracker : SciBar type
Extruded Scintillator + Wave Length Shifting Fiber

3°36m~14m1m

νµµIronVeto all surface
by plastic scintillator(Fibers goes through holes.)

1m
1m
1m

3m

3m20mΦ

7

neutrinos at on-axis~0.2 events/ton/spill

ProfileSpectrum

8neutrinos at off-axis

Beam OA2.5deg~0.06 events/ton/spill

Eν

1.8°

2.0°

2.2°

SK
ND

SKND

SKND

Eν

Eν

0.2° ⇒ 1m at the detector position.
It will be a useful tool to study neutrino interaction.
9

Physics objects (momentum) at off-axis
νµfrom π+from K+

muon from π+from K+

Peak 300~400MeV/cfrom π+νe from K+
from K0from π+electronfrom K+from K0

10

A detector Design
Muon Range Detector(Fe + RPC or Drift tube planes)µ+γ catcher(sandwich detector)

Full activeDetector
like K2K SciBar(+ water target)

11

Hadron-Production Model dependence
on the Far/Near ratio
2.5[Far/Near ratio]Eν @280m off-axis

x10 3
1600

MARS
FLUKA

1400
1200
1000

MARS
FLUKA

800
600
400
200
0000.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.

Eν[GeV]

0012

Flux @SK = Flux @ND ×[Far/Near ratio]
From MC simulation

1.2Double ratio (FLUKA/MARS)The Difference of Far/near ratio is～1.2±0.6%

1.0(Energy range:0.4～1.2[GeV])

0.80

The effect may be small! ← to be checked!

1Eν[GeV]212

3. Medium Neutrino Detector (2km from the target)
There is a place to be rent
for the experiment.
• Almost same Eν as SK• Water Cherenkov can beoperated (~1 events/kt/spill).
Spectra at different positions
x 10 32km

1800

1600

1400

295km

1200

1000

800

600

0.28km

400

200

000.5

111.5

222.5

333.54 Eν (GeV)
44.55Eν (GeV)13

A 2km Detector
Fine grained
scintillater detector

Water Cherenkov
detector

Muon detector

8m4m

ν beam

8m

8m
16m
3m×5m×5m

5m
Total mass :9.2m φFid. Mass :100ton1000ton14

Measured Eν spectrum
Medium Detector
SK

Almost same

Reconstructed Eν (MeV)15

4. Summary• Two types of near neutrino detector
at on-axis and off-axis is necessary
to monitor the neutrino beam.
• A medium neutrino detector isessential to reduce the beamsystematic and test the waterCherenkov reconstruction.

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