1. Conventional Neutrino Beam Experiment : JHF – Super-Kamiokande
Yoshihisa OBAYASHI
(Kamioka Observatory, ICRR)
Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

2. JHF Neutrino Working Group
Y. Itow, Y. Obayashi, Y. Totsuka (ICRR)
Y. Hayato, H. Ishino, T. Kobayashi,
K. Nakamura, M. Sakuda (KEK)
T. Hara (Kobe)
T. Nakaya, K. Nishikawa (Kyoto)
T. Hasegawa, K. Ishihara, A. Suzuki (Tohoku)
Konaka (TRIUMF)
Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

3. Overview of JHF – SK nm→nx disappearance: nm→ne appearance:
Precise measurement of oscillation parameters:
d(Dm232)~ 2x10-4eV2,
d(sin22qmx)~ 1%
nm→ne appearance:
Explore down to
sin22qme ~ 5x10-3
Oscillation En=0.5~1.2GeV
P=sin22q・sin2(1.27Dm232L/En)
Dm232=2~5x10-3eV2, L=295km
Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

4. JHF (Japan Hadrons Facility)
Tokai-mura
Construction:
2001 ~ 2006 N
50GeV PS
3GeV PS
Neutrino Beam Line
600MeV Linac
Front Detector(s)
To Super-Kamiokande
J H F
MINOS
K 2 K
E(GeV) 50
120 12
Int.(1012ppp)
330 40 6
Rate(Hz)
0.29
0.53
0.45
Power(MW)
0.77
0.41
0.0052
1021p.o.t./1year(130day)
Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

5. Far Detector Super-Kamiokande @ Kamioka Operation Start: 1996
295 km from JAERI
50.0kt Pure Water in the tank
22.5kt Fiducial Volume as a neutrino target
Energy measurement by total amount of Cherenkov light
e-m separation is performed by ring pattern likelihood
Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

6. Neutrino Beam at JHF Three Possible options: Present Strategy:
Wide Band Beam (WBB)
2 horns, almost same as K2K
Narrow Band Beam (NBB)
Horn(s) + Bending
Off Axis Beam
Another option of NBB
Present Strategy:
First 1(~2) year:
High Statistics Run with WBB
Pin down Dm2
Next 5 years:
Precise Analysis with (one of) NBB
Measurement of q23,q13
Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

7. Wide Band Beam High Intensity Wide sensitivity in Dm2
Established technique
Backgrounds from HE tail
Spectra diff. btw near&far
Systematic error
Needs Heavy shielding
decay pipe must be short
~ 4200 nm int./22.5kt/yr
(ne:0.8%)
Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

8. Narrow Band Beam Less systematic error Less BG from HE tail
Easy to tune En
Less shielding
Low intensity
~ 830 nm int./22.5kt/yr
Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

9. Off Axis Beam: Another option of NBBq
WBB with intentionally misaligned from detector axis
Quasi Monochromatic Beam
Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

10. Off Axis Beam More intense than NBB More HE tail than NBB
Hard to tune En
Needs heavy shielding
Not established technique
Beam monitor
Near/Far ratio, …
~ 2200 nm int./22.5kt/yr
Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

11. Physics Sensitivity
Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

12. nm Disappearance Ratio after BG subtraction: Fit with
1-sin22q・sin2(1.27Dm2L/E)
Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

13. nm Disappearance d(sin22q)~0.01 in 5 years Possible systematic errors:
inelastic cross section: 20%
4%・E
Spectrum diff.(Near/Far): 10%
Energy measurement: %
d(sin22q)~0.01 in 5 years
Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

14. nm → ne Appearance Three flavor oscillation framework:
Dm212 <<Dm223 ~Dm213≡Dm2
Dm223= Dm2atm>10-3eV2
Dm212= Dm2sol<10-4eV2
Oscillation Probability P :
Present limit: sin22qme > 5x10-2
sin22qme= sin22q13・ sin2q23
sin22q13 <0.1(CHOOZ)
sin2q23 ~ 0.5 (Atmospheric n)
Goal: sin22qme ~ 5x10-3
m22
m12
m32
Dm2atm
Dm2sol
Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

15. ne nm m easy to reject Signal & Backgrounds
Signal: ne C.C. interaction
BG 1: nm C.C. interaction
Single fuzzy ring
Cherenkov angle
~ 42deg. ne
e+- shower
Sharp ring edge
Cherenkov angle
< 42deg. nm m
easy to reject
Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

16. Backgrounds (continued)
BG 2: N.C. p0 production n n
p0→2g
2 showers
2 fuzzy rings → hard to separate
Not reproduce En
need effort to reject
Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

17. ne Selection by SK Official Cutsnm
(w/p0) ne
Fid. Vol.
3651
795
53.3
1R e-like 92 68
29.5
reduct.rate
2.5%
8.6%
1.8%
sin22qme=0.05,
Dm2=3x10-3eV2
S/N ~ 1/3
Main Background come from p0
Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

18. p0 rejection Force to find 2nd g ring Cut with follow quantities:
Shower direction w.r.t. n
(cosqne)
Energy fraction of second g R(g2)=E(g2)/(E(g1)+E(g2))
Pattern likelihood difference
Invariant mass of 2 g
Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

19. p0 cut efficiency PRELIMINARY WBB 1year NBB 1year Off Axis 1year WIDEnm ne
Fid. Vol.
3651
53.3
1R e-like
92(2.5%)
29.5(55.3%)
p0 cut
4.0(0.1%)
9.8(18.4%)
NBB 1year
LE2p nm ne
Fid. Vol.
740
23.0
1R e-like
13.2(1.8%)
16.2(70.4%)
p0 cut
1.8(0.2%)
11.6(50.4%)
Off Axis 1year
2deg. nm ne
Fid. Vol.
1801
45.5
1R e-like
37.4(2.1%)
32.1(70.5%)
p0 cut
3.8(0.2%)
24.3(53.4%)
sin22qme=0.05,
Dm2=3x10-3eV2
Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

20. nm → ne Oscillation Sensitivity
PRELIMINARY
10% systematic in
BG rate is considered
by 5year run of NBB (off axis beam)
Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

21. nm → ne Oscillation Sensitivity
PRELIMINARY
10% systematic in
BG rate is considered
Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

22. Comparison to MINOS
MINOS
Ph2he,me,le
2yr exposure
(hep-ph )
JHF neutrino is more sensitive especially in Atmospheric Dm2 region
Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

23. nm→ nt? nsterile? nm nt nsterile nt ⇔ nsterile discrimination
NC p0 production:
n + N → n + N + p0
In the case of nm→ nsterile oscillation,
Number of p0 also decrease
nt ⇔ nsterile discrimination CC NC nm
Yes nt
Few
nsterile No
Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

24. nm disappearance search
Summary
JHF neutrino experiment
Expected to start in 2006
Far Detector: Super-K
By 5 years of run:
nm disappearance search
d(Dm2) ~ 2x10-4eV2
d(sin22q) ~ 1%
ne appearance search
sin22qme ~
nm⇔nt or nm⇔nsterile
Can be tested
Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

25. Test of CP Violation If sin22q13 ~ 0.01: 1MW(2deg. off axis) → SK :
2 nm → ne / year
Too few to see CP
4MW → Mton :
300 nm → ne / year
100 nm → ne / year
1year n + 3year n
600 total events with asym: 150xsind
d=30deg.(3s), 12deg.(90% CL)
Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000