Super-Kamiokande

May 26, 2006 

Vulcano Workshop 2006 

Super-Kamiokande 

~The Status of n Oscillation ~ 

Yoshihisa OBAYASHI 

(ICRR, Univ. of Tokyo) 

for Super-Kamiokande Collaboration 

May 26, 2006 

Y.Obayashi @ Vulcano 2006 1

News: SK is Fully Reconstructed! 

• Apr. 2006 All PMTs are mounted with 

acrylic/FRP covers and start water filling 

May 14: Celebration for SK 10 th 

anniversary and Commissioning 

of SK-III 

PMT with cover 

Many T2K collaborators took 

reconstruction shifts 

Now: Half of tank is filled with water 

• End of Jun. 2006: Filled with water and restart 

observation 

May 26, 2006 Y.Obayashi @ Vulcano 2006 

2

42 m 

Super-Kamiokande 

• 50kton pure water (22.5kt fid.vol.) 

• 11200 (Inner detector) + 1800 

(Outer detector) PMTs 

• 1000m underground 2700m 

wat. eq. 

39.3 m 


3


4 

History 

1996 

1997 

1998 

1999 

2000 

2001 

2002 

2003 

2004 

2005 

2006 

2007 

2008 

Start 

SK-I 

SK-II 

SK-III 

# of PMT 

(Photo Coverage) 

11,146 

(40%) 

Accident 

Partial Reconstruction 

Full Reconstruction 

5,182 

(19%) 

11,129 

(40%) 

Energy Threshold 

(Solar n) 

5 MeV 

7 MeV 

4 MeV(plan) 

Major Physics 

Outputs 

Atm. n Oscilaltion 

Phys. Rev. Lett. 81,1562(1998) 

Solar n Oscilaltion 

Phys. Rev. Lett. 86,5651(2001) 

Atm. n L/E 

Phys. Rev. Lett. 93, 101801(2004) 

K2K Final Result

Overview 

Atmospheric Neutrinos 

nm disappearance analysis 

nm nt or other modes 

Solar Neutrinos 

SK-I results 

SK-II update 

Improvement for SK-III 

Supernovae Neutrinos 

Summary 


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6 


p, He … 

Zenith angle 

Q 

Downward 

(L=10~100 km) 

Event 

Classification 

p ± , K ± 

m ± 

Fully Contained 

(FC) (E n ~1GeV) 

n m 

e ± 

Partially Contained 

(PC) (E n ~10GeV) 

n m 

n e 

Upward 

(L=up to 13000 km) 

Stopping m (E n ~10GeV) 

Through-going m (E n ~100GeV) 

Particle ID 

(Fully Contained) 

e- like mu- like


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Zenith Angle Distribution 

SK-I : 1489 days 

SK-II : 804 days 

n m –n t oscillation (best fit) 

null oscillation 

FC 

FC 

< < 

FC 

FC 

FC 

> 

FC 

> 

FC 

FC


8 

Oscillation Analysis 

m/e double ratio allowed region (n m n t ) 

Update from 

Phys. Rev. D 72, 052007 (2005) 

(SK-I results) 

Sub-GeV 

SK-II : 

SK-I : 

( m / e) 

( m / e) 

DATA 

MC 

0.656 

0.022 

0.033 

0.658 

0.016 

0.035 

Best Fit: Dm 2 = 2.5 x 10 -3 eV 2 

sin 2 2q = 1.00 

c 2 = 839.7 / 755 dof (18%) 

Multi-GeV (FC+PC) 

( m / e) 

DATA 

0.047 

SK-II : 0.7460 .044 

0. 055 

( m / e) 

MC 

SK-I : 

0.702 

0.032 

0.030 

 

0.101 

1.9 x 10 -3 eV 2 < Dm 2 < 3.1 x 10 -3 eV 2 

sin 2 2q > 0.93 at 90% CL

L/E analysis 

Update from 

Phys. Rev. Lett. 93,101801(2004) 

• 

• Select good L/E resolution (


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L/E Analysis result 

Zenith angle binning 

Oscillation 

Decay 

Decoherence 

c 2 osc 

c 2 dcy 

c 2 dec 

= 83.9/d.o.f 

= 107.1/d.o.f, Dc 2 = 23.2(4.8σ) 

= 112.5/d.o.f, Dc 2 = 27.6(5.3σ)


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3 Flavor Oscillation 

Submitted to Phys. Rev. D, 

see hep-ex/0604011 

• In the case q 13 ≠0: 

ne excess may be seen 

• Matter effect enhance n e appearance 

vacuum 

matter 

nm ne oscillation probability, 

Dm 2 =2.5x10 -3 eV 2 , 

sin 2 q 23 =0.5, 

sin 2 q 13 =0.04

3 Flavor Analysis Result 

• Excess of up-going ne 

– SK-I data shows 

no excess yet 

• Allowed region 

– Consistent with pure nmnt 

SK-I 

1489days 

Best fit 

(Dm 2 =2.5 

x10 -3 eV 2 , 

sin 2 q 23 =0.5, 

sin 2 q 13 =0.0) 

Expected excess 

(Dm 2 =2.5x10 -3 eV 2 , 

sin 2 q 23 =0.5, 

sin 2 q 13 =0.04) 


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Tau Appearance Search 

• Tau Enrich Sample: 

– Evis>1.33GeV (Multi-GeV) 

– Most energetic ring is e-like 

– Likelihood selection 

• Visible Energy 

• Sphericity 

• Distance between n interaction and 

decay-e 

• Zenith angle fit with tau signal and 

nm background 


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14 

n m n t or n sterile 

Admixture model: 

Consistent of 0% of n s , 

Arrow ~25% of sterile 

at 90% CL


15 

Other than Oscillation 

LIV 

S.Coleman & S.L. Glashow PRD 59(116008),1999 

V.Barger et. al., PRL 85(24),2000 

2 

 

 

2 2 

Dm 

 

P OSC 

sin 2q 

sin 1.27 

2Db 

L 

E 

• Best fit: c2(377dof)=399, 

(a=0.053,sin2q v =0.093) 

• a


16 


• 8 B neutrino – electron scattering n + e - → n + e - 

SSM Expectation 

Typical Solar n event 

5.94(1+/-0.01)x10 10 /cm 2 /s (BP04 SSM) 

5.79(1+/-0.23)x10 6 /cm 2 /s 

8 

B 

Ee = 9.1MeV 

cosqsun = 0.95

Solar n Data of SK-I 

May 31, 1996 – July 13, 2001 (1496 days ) 

n + e - n + e - 

22400230 solar n events 

(14.5 events/day) 

8 

B flux : 2.35 0.02 0.08 [x 10 6 /cm 2 /sec] 

Data 

SSM(BP2004) 

= 0.406 

0.004 

+0.014 

-0.013 


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n e and n m +n t Fluxes(SK and SNO Results) 

SK 

SNO 

ES = 2.350.09 [x10 6 /cm 2 /s] 

CC = 1.720.08 

ES = e +0.15 m,t 

CC = e 

SNO NC = 4.980.35 NC = e + m + t 

(cf. SSM(BS2005) = 5.69±0.93) 

Obtained total flux: exp = 5.2±0.3 

SK 

SNO CC 

SNO NC 

± 

(BS2005)


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Energy spectrum of SK-I 

(tan 2 q, Dm 2 ) 

Energy correlated systematic error


20 

Solar n results from SK-I 

Region represents 

allowed values of 

neutrino properties


21 

SK-II Solar n data 

(Preliminary)

Energy Spectrum 


22


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P(n e → n e ) 

E 

May 26, 2006 n (MeV) 

Y.Obayashi @ Vulcano 2006 

25 

Solar n @ SK-III 

n e survival probability 

Recoil electron spectrum 

To see ~10% spectrum distortion, 

Lower energy threshold 

Minimize statistic error 

Minimize systematic error 

sys. error 

sin 2 (q) 

0.35 

0.28 

0.28 

0.28 

0.22 

Dm 2 (eV 2 ) 

6.3 x 10 -5 

4.8 x 10 -5 

7.2 x 10 -5 

10.0 x 10 -5 

7.2 x 10 -5


26 

Background from Radon @ SK-I 

Y.Takeuchi et al., PLB452(1999)418

Improvement 


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Supernova Neutrino Bursts 

No candidate was found in SK-I and SK-II 

2.3 

T 

< 0.39 SN/yr (90%CL) 

Upper limit of galactic SN rate < 

Efficiency vs. Distance 

T: measurement time


29 

Supernovae Relic Neutrinos 

Reactor n 

Solar 8 B 

Solar hep 

Expectations 

Population synthesis (Totani et al., 1996) 

Constant SN rate (Totani et al., 1996) 

Cosmic gas infall (Malaney, 1997) 

Cosmic chemical evolution (Hartmann et al., 1997) 

Heavy metal abundance (Kaplinghat et al., 2000) 

LMA n oscillation (Ando et al., 2002) 

Atmospheric n 

Phys. Rev. Lett. 90, 061101(2003) 

SK-I 

Total background 

Atmospheric n m → 

invisible m → 

decay e 

90% CL limit 

of SRN 

Atmospheric n e


Summary 

Oscillation analysis result based on SK-1 (1489d) +SK- 

2(890d) is presented 

Further analysis based on SK-I(1489d) 

Consistent with nm nt oscillation. 

Some non-tau modes: unlikely 


Oscillation analysis based on SK-I(1469d) is presented 

SK-II data also analyzed though energy threshold is 

7MeV 

Improvements for SK-III is going on 

Upper limits for SN and SRN rate obtained 


30

Supplements 

May 26, 2006 

Y.Obayashi @ Vulcano 2006 31

Tau Appearance Search 


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Zenith Angle Distributions (SK-I bins) 


null oscillation


34 

Zenith Angle Distributions (SK-II bins) 


null oscillation

SK-I + SK-II combined analysis (data binning) 

P lep 

Sub-GeV Multi-GeV 

CC n e CC n m 

FC FC FC FC 

UP through 

PC PC 

1ring mring 1ring mring 

showering 

stop thru 

e-like e-like m-like m-like 

UP through 

non-showering 

38 event type and 

momentum bins 

UP 

x 

stop 10 zenith bins 

380 bins 

Since various detector related systematic errors are different, 

we do not combine the SK-I and SK-II bins. 

380 bins for SK-I + 380 bins for SK-II 760 bins in total

SK-I + SK-II combined analysis (systematic errors) 

neutrino flux (14) 

neutrino interaction (12) 

Identical for SK-I and SK-II 

solar activity (1) 

event selection 

and reconstruction (21) 

Regarded as independent 

between SK-I and SK-II 

The total number of systematic errors is : 

Flux (14) + Interaction (12) + SK-I (22) + SK-II (22) = 70

Result from SK-I + SK-II data 

SK-I : 1489 days 

SK-II : 804 days 

Best Fit: Dm 2 = 2.5 x 10 -3 eV 2 

sin 2 2q = 1.00 

c 2 = 839.7 / 755 dof (18%) 

1.9 x 10 -3 eV 2 < Dm 2 < 3.1 x 10 -3 eV 2 

sin 2 2q > 0.93 at 90% CL

SK+ K2K Combined Results 

K2K 

K2K 

Combine 

Combine 

SK 

SK 

Combined result sin 2 2q Dm 2 [eV 2 ] 

Best fit point 1.03 2.4910 -3 

Best in phys. 1.00 2.5110 -3 

Arrowed region of Dm 2 @ 

sin 2 2q1 

2.29(-9%) ~ 2.84(+13%) [eV 2 ] (68%) 

2.17(-14%) ~ 3.03(+21%) [eV 2 ] (90%) 


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Super-Kamiokande

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