K2K and JHF near detectors

NuFact02, July 2002, London

Takaaki Kajita, ICRR, U.Tokyo

For the K2K collab. and JHF-Kamioka WG

• K2K near detector system

• Basic idea for JHF near detectors

• Summary

Outline

Bird’s Eye Neutrino Beam Line

200m

Front (Near) Detector

K2K experiment @KEK

K2K near detector

flux anddirection

312 ton (1ev / 20spills)

6 ton 25 tonFid. Vol.:

(MRD)

(SciFi) (1Kton)

300m from the target

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.

Role of the SciFi detector

p

μ

SciFi

MRDMax osc.

Fraction of non-quasi-elastic events must be understood well.

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.

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

JHF near detectors

280m

First near detector @280m from the target

Target

Second near detector @～ 2km from the target

Decay pipe (L=130m)

ν

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

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)

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)

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….

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

Stopping point distribution of muons

ν

Edge of the fid vol.

2m

4m

Detector surface

Measured by muon detector

The detector should look like….

Water Ch.

Scintillator detector

Muon counter

Surface building

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.

End

Beam energy stability ? (MRD, 1Kton)

Everymonth

Eμ (GeV)

MRD 1Kton

2000

2001

Pμ(GeV/c)