1. スーパーカミオカンデ１１４０日の 大気ニュートリノ観測
日本物理学会＠新潟大
2000. Sep. 22
スーパーカミオカンデ１１４０日の 大気ニュートリノ観測
nm → nt　２世代解析
nm-nt-ne　３世代解析
n n　ratio の測定
大林　由尚　（東京大学宇宙線研究所）
他　Super-Kamiokande　Collaboration

2. Event Categories nm CC, ne CC, NC nm CC ~100GeV (Through m)
Fully Contained (FC)
nm CC, ne CC, NC
<En>~1GeV
Partially Contained (PC)
nm CC
<En>~10GeV
Upward Going Muon (Upm)
<En>~10GeV (Stop m)
~100GeV (Through m)

3. Observed Events (SK 1140day)
Sub-GeV (Evis<1.33GeV)
Multi-GeV (Evis>1.33GeV) FC
DATA MC
single ring
5017
6023.5
e-like
2531
2402.6
m-like
2486
3620.9
multi ring
1885
2321.5
TOTAL
6902
8345.0 FC
DATA MC
single ring
1078
1294.1
e-like
576
555.4
m-like
502
738.7
multi ring
1198
1470.1
TOTAL
2276
2764.2 PC
665
945.1

4. Zenith Angle P(osc)= sin22q・sin2(1.27Dm2L/E) U/D(Multi-GeV FC+PC)=
●DATA ーMC(w/o osc.) ーMC(w/ osc.)
Zenith Angle
P(osc)=
sin22q・sin2(1.27Dm2L/E)
U/D(Multi-GeV FC+PC)=
0.54±0.04±0.01

5. 2 Flavor Oscillation Analysis (nm-nt)
Oscillation Analysis by FC + PC + Upmu
Best Fit: c2min=135.4/152d.o.f
＠ sin22q= Dm2=3.2x10-3eV2
Assuming null osc.: c2min=316.2/154d.o.f
Allowed
0.88<sin22q
1.5x10-3<Dm2<5x10-3
(eV2)

6. 3 Flavor Oscillation Analysis (nm-nt-ne)
Dm2atm
Approximation:
Dm223>> Dm212
Dm223= Dm2atm>10-3eV2
Dm212= Dm2sol<10-4eV2
Dm223 ~Dm213 ≡Dm2
Osc. Probability:
Parameters:
(sin2q13,sin2q23,Dm2)
Matter effects
considered as 5 step density function
m22
Dm2sol ( )
m12

7. 3 Flavor Analysis Result
Data Set: FC + PC
Best Fit: (ê)
sin2q13=0.019,
sin2q23=0.55,
Dm2=2.5x10-3eV2
Consistent with
pure　maximal nm→nt(Ñ)
Consistent with CHOOZ ê Ñ ê ê

8. Measurement of nm - nm ratio
Motivation:
A test of the atmn flux prediction
In the case of
nm+ N → m- X :
m- can be captured by nucleus
# decay electron ↓
(m- life → short)
Data & MC are consistent within 1s

9. Summary nm – nm ratio: Atmospheric Neutrino @ Super-Kamiokande
Livetime: 1140days
2 flavor oscillation analysis:
Mixing angle: sin22q>0.88,
Mass difference: Dm2=1.5~5x10-3eV2
3 flavor analysis:
sin2q13<0.34
consistent with pure nm→nt, CHOOZ
nm – nm ratio:
Data & MC are consistent within 1s

10. Transparencies for the Back Pocket

11. Atmospheric Neutrino
Production
Flavor ratio

12. Super-Kamiokande 50.0kt Pure Water 22.5kt Fid.Vol. 1000m UnderGround
(2700m.w.e.)
11146 PMTs for ID
1885 PMTs for OD
Operation started in Apr. 1996

13. Oscillation Analysis with 3D Flux Calculation
Preliminary
Oscillation Analysis by FC + PC + Upmu
Best Fit: c2min=147.8/152d.o.f
＠ sin22q= Dm2=3.5x10-3eV2
Incl. Unphys. Region: c2min=146.7/152d.o.f
＠ sin22q= Dm2=3.5x10-3eV2

14. nt or nsterile? nm→nsterile oscillation is disfavored at 99% C.L.
NC enrich
#ring>1
e-like
Evis>400MeV
High E PC
Evis>5GeV
Up thru m