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

2. K2K near detector system Basic idea for JHF near detectors Summary Outline

3. Bird’s Eye Neutrino Beam Line 200m Front (Near) Detector K2K experiment @KEK

4. K2K near detector flux and direction 312 ton (1ev / 20spills) 6 ton25 tonFid. Vol.: (MRD) (SciFi) (1Kton) 300m from the target

5. Beam direction? (MRD) profile x profile center x (cm) profile center y (cm) June 99 Apr. 01  1mrad (0.5GeV < Eμ < 1.0GeV) (1.0GeV < Eμ < 2.5GeV) ±3-4 mrad. accuracy required.

6. Role of the SciFi detector p μ SciFi MRD Max osc. Fraction of non-quasi-elastic events must be understood well.

7. 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 θ > 90 degree.

8. 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 1.8m Δm 2 =3×10 -3 eV 2 Eν=600MeV. Lower energy ν interactions should be studied. 45,000 events @3×10 19 pot

9. JHF near detectors 280m First near detector @280m from the target Target Second near detector @ ～ 2km from the target Decay pipe (L=130m) ν

10. Required accuracy Discovery of non-zero θ 13 Precise measurement of θ 23 and Δm. CP violation JHF-Phase IJHF-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

11. Some information on the beam…. Number of events /100MeV/yr Eν(GeV) Max. osc. (must be predicted accurately) Background (must be understood well)

12. 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) ( φ far / φ near )×(L far / L near ) 2 2 1 1 0 0 @280m @2km Not a good place…. OK ! 0123 E ν (GeV)

13. Near detector @280m Beam profile monitor Cannot be water Cherenkov Detailed study of neutrino interactions @1GeV No detailed design….., but could be something like: ・・・・ 10m ? 0 deg. Super-K ※ This profile is obsolete… Just to give the idea….

14. Near detector @2km Details : not designed yet 9.2m φ 15.2m 8m 4m Total mass : 1000ton Fid. Mass : 100ton ν beam Fine grained scintillater detector 5m 8m Water Cherenkov detector Muon detector

15. Stopping point distribution of muons ν Edge of the fid vol. 2m 4m Detector surface Measured by muon detector

16. The detector should look like…. Water Ch. Scintillator detector Muon counter Surface building

17. 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 > 2km.

18. End

19. Beam energy stability ? (MRD, 1Kton) Every month E μ (GeV) MRD1Kton 2000 2001 P μ (GeV/c)