1. Prospects of J-PARC Neutrino Program
Changgen Yang
Institute of High Energy Physics
Beijing

2. Overview of J-PARC expect to start in 2007
approved
~1GeV n beam
Super-K: 22.5 kt
Hyper-K: 1000 kt
0.77MW 50 GeV PS
4MW 50 GeV PS
( conventional n beam)
Phase-I (0.77MW + Super-K)
Phase-II (4MW+Hyper-K) ~ Phase-I  200

3. J-PARC AERI@Tokai-mura (60km N.EJ. of KEK) Construction 2001～2006
MINOS
K2K
E(GeV) 50
120 12
Int.(1012ppp)
330 40 6
Rate(Hz)
0.292
0.53
0.45
Power(MW)
0.77
0.41
0.0052
(60km N.EJ. of KEK)
Construction
2001～2006
(280m from target)
(Approved in Dec.2000)

4. JHFnu: K2K as an example nm m+ p+ ＳＫ FD Target+Horn 200m decay pipe
~250km FD
Pion monitor
(PIMON)
MUMON

5. Three Beams Wide Band Beam Narrow Band Beam Off Axis Beam q Intense
Wide sensitivity in Dm2
BG from HE tail
Syst. err from spectrum extrapolation
Wide Band Beam
2horns
Narrow Band Beam
Less HE tail
Less sys err from spectrum
“counting experiment”
Easy to tune En
momentum selected p
Off Axis Beam
High int. narrow band beam
More HE tail than NBB
Hard to tune En q
Horns
Decay Pipe
Far Det.

6. q
Target
Horns
Decay Pipe
Far Det.
Off Axis Beam

7. Comparision of Spectra
800MeV~1GeV
Sharp peak for NBB/OAB
OAB produce very intense “NBB”
WBB:5200 CC int./22.5kt/yr
NBB: 620 CC int./22.5kt/yr (2GeV/c p tune)
OAB: 2200 CC int./22.5kt/yr (2degree)

8. ne contamination Very small ne/nm ratio at nm spectrum peak: 1~2x10-3
NBB (LE2p)
OAB (2degree)
m-decay
m-decay
K-decay
K-decay
0.73%
1.0%
Very small ne/nm ratio at nm spectrum peak: 1~2x10-3

9. Requirement of Near Detector:
Measure the quality of neutrino beam
Estimate the neutrino flux and the energy spectrum at Super-K
Study neutrino interactions to estimate b.g. for oscillation analysis
Measurements of the neutrino beam:
Direction;
Flux/spectrum for  and e
Profile
Stability
Event types(QE, single  ,NC pi0 etc…)

10. One example of Near Detector

11. Far/Near ratio (OA 2 deg)

12. Intermediate Detector

13. A tool: Pion Monitor(PIMON)
nm disappearance
F/N extrapolation (incl. HE tail)
Kaon production(p/K ratio)  HE tail
ne appearance
BG : NCp0: ne~1:1, half of p0 BG from HE tail
F/N extrapolation  HE tail
Kaon production(p/K ratio)  HE tail
 ne contamination
Neutrino int. study at 280m
Precise spectrum information

14. Far detector: Super-Kamiokande

15. Physics Goal of JHFnu(Phase I)
L=295km, En=0.5~2GeV(Match the WCD)
Precise determination of neutrino oscillation parameters:
sin2223  1%
m232  1×10-4eV2
at (sin22q=1.0, Dm2 =3.2×10-3eV2)
sin2213  < 1%
Physics Goal of JHFnu(Phase II)
CP violation measurement
Proton decay

16. Neutrino Energy Reconstruction
Assume CC quasi elastic (CCQE) reaction
nl + n → l + p n l- p
(El , pl) ql

17. Neutrino Energy Reconstruction
Quasi-elastic
s=80MeV
En(reconstruct)
En (True)
En(reconstruct) – En (True) (MeV)
QE dominate at ～1GeV

18. Dm232 and q23 measurement
P(nm→nm)=1 - cos4q13 sin22q23 sin2(1.27 Dm232 L/E) ~1
P(nm→ nm )
sin22q
Dm2
En (GeV)

19. Reconstructed En (MeV)
nm disappearance
1ring FC m-like
Ratio after BG subtraction
(linear)
Dm2=3×10-3 sin22q=1.0
Oscillation with
Dm2=3×10-3
sin22q=1.0
Non-QE
(log)
No oscillation
~3%
Reconstructed En (MeV)
Fit with 1-sin22q・sin2(1.27Dm2L/E)

20. q13 measurement P(nm→ne)=sin22q13 sin2q23 sin2(1.27 Dm232 L/E)
A mixing angle between 1st and 3rd generation , q13 may be not very small
A discovery of nm→ne can open the new window to study CP violation in this mode
May be a source of baryogenesis in the universe

21. ne appearance ×20 improvement
Background rejection against NC p0 is improved.
sin22qme=0.05 (sin22qme  0.5sin22q13)
Dm2
CHOOZ
×20 improvement 3 5
×10-3
sin22qme

22. Non standard n oscillation
A sterile neutrino (LSND result? 3 or 4 n’s)
with nm nm /ne measure: nm nt ( / ns )
non standard CP violation of nm→nt .
Any other unexpected phenomena

23. nm →nt confirmation NC p0 interaction (n + N → n + N + p0)
nm ne CC + NC(~0.5CC) ~0 (sin22qme~0)
nm CC + NC(~0.5CC) ~0 (maximum oscillation) nt NC
#p0 is sensitive
to nt flux.
OAB
nm nt
nm ns
D=390±44
#p0 + #e-like
Dm232
3.510-3

24. n detector Phase-II: Hyper-K 1,000 kt Far n detectors Phase-I: Suker-K
22.5kt (50kt)

25. Search for nmne sin22qme sensitivity 310-3 Phase-II Phase-I ~310-4
102
Exposure/(22.5kt1021pot)
p0 background has to be understood with 2% level.
(n physics at a front detector)

26. CP violation in n oscillation
L=295km : small MSW En~1 GeV : large CP asym.
If LSND is true, CP violation may be much larger than expect.

27. CP Violation Study Compare nmne with nmne Dm122 =5×10-5eV2 ,
sin22q13 = 0.01
q23 = p/4, q12 = p/8
Compare nmne with nmne
N(e+)
NO CP violation
w/o matter effect.
|d|>20 (3s discovery)
3s discovery
90% C.L.
N(e-)

28. Analysis for discovery of p→e+π0
Tight momentum cut
⇒ target is mainly free protons
efficiency=17.4%, 0.15BG/Mtyr
free proton
bound proton
Small systematic uncertainty of efficiency
High detection efficiency
Perfectly known proton mass and momentum
No Fermi momentum
No binding energy
No nuclear effect

29. How the signal looks like
Proton mass peak
can be observed !
τp/B(p→e+π0) = 1×1035 yrs
S/N = 4 for 1×1035 years ↓
S/N = 1 for 4×1035 years
τp/B(p→e+π0) = several×1035 yrs is reachable by a large water Cherenkov det.

30. Physics Reach Phase-I (0.77MW + 22.5kt): Phase-II (4MW + 1000kt):
NC interaction: Establish nmnt and limit on nmns
nmnm : dsin22q23 < 0.01
nmne : sin22q13 < 6×10-3 (90% CL)
nmnm : dDm < 1×10-4eV2
at (sin22q=1.0, Dm2 =3.2×10-3eV2)
Phase-II (4MW kt):
nmne : sin22q13 < 1×10-3 (90% CL)
nmne vs nmne : |d| >20 (3s discovery)
at (Dm122 =5×10-5eV2 , Dm232 =3×10-3eV2)

31. q13 measurement:superbeams vs. reactor
P. Huber et al., hep-ph/
400 tGWy
8000 tGWy
Systematics
Correlations
Degeneracies

32. To get funding for the 2 km Detector?
To get additional funding for the Experimental hall + Detector (from KEK for JPY 2004?)
The availability of the candidate site for the 2 km detector
Realistic design and cost estimation of the detector hall

33. Schedule (4 year plan)  KEK(~163 M$)
MEXT(Ministry of Education,Science and Technology)
Council for Science and Technology Policy
 Ministry of Finance
Need re-consideration for JFY 2004