1DISCOVERY OF ATMOSPHERIC MUON NEUTRINO 　 OSCILLATIONS

Prologue First Hint in Kamiokande Second Hint in Kamiokande Evidence found in Super-Kamiokande Nov-12 Accident Progress in the K2K Experiment Future

Yoji TotsukaFor

Kamiokandeand

Super-KamiokandeCollaborators

2Kamiokande Detector(Kamioka Nucleon Decay Experiment)

Search for proton decay3000ton water1000 50cm PMT (20% photo coverage)1000m undergroundMin det. energy ~ 20 MeV (later ~ 7 MeV)1983-1996

3Atmospheric Neutrinos (1)

The most severe background to proton decay search

100MeV – 1000GeV : e ~ 2 : 1

(low E)p, He

νe

Super-K

μ±

νμ

π±

atmosphere

e±

earth

4

Interaction in the rock

FC + PC

through-going muons

stopping muons

Initial neutrino energy spectrum

FC

Through-going muons

Stopping muons

Event topology

PC

e + N e + X + N + X + N + X

5First Hint (2.87kt·yr, 1988)

data MC

events e events e

single ring

178 60(0.34±0

.05)

232.5 110.3(0.47)

-like 85 52 144.0 103.8

e-like 93 8 88.5 6.5

6/e Identification with a test beam

7

Earth

Up-down symmetryof the flux

Atmospheric Neutrinos (2)

8Second Hint (7.7kt·yr, 1994)

sub-GeV data MC

events e events e

single ring 482 182 584.3 270.5

-like 234 158 356.8 247.9

e-like 248 24 227.6 22.6

9

４０ｍ

４１．４ｍ

Super-Kamiokande (1996)1996-50000ton water11146 50cm PMT (40% photo coverage)1000m undergroundMin det. energy ~ 5 MeV

10Evidence for Oscillation of Atmospheric Neutrinos(33.0kt·yr, 1998)

sub-GeV data MC (+-20%)

single ring 2389 2622.6

-like 1158 1573.6

e-like 1231 1049.1

11Upward-going muons

12

2=170.8/170 d.o.f. at (sin2223, m232)=(1.00, 2.0x10-3eV2)

2=445.2/172 d.o.f. (null oscillation)

1489 day FC+PC data + 1646 day upward going muon data

13Allowed region of the oscillation parameters

Assuming oscillation

Best fit 2

min = 170.8/170 d.o.fat (sin2223 m23

2) = (1.0, 2.0 x 10-3 eV2)

90% CL allowed regionsin2223> 0.91.3x10-3 < m23

2 <3.0x10-3 (eV2)

Assuming null oscillation 2 = 445.2/172 d.o.f

(complete SK-I dataset)

Soudan-2

MACRO

Super-K68% CL90% CL99% CL

14Nov-12 Accident

6777 ID + 1100 OD PMTs destroyed

15

Partial rebuilding 5248 ID PMTs

(47% of pre-accident density) 1885 OD PMTs Ready by end 2002

Full rebuilding Additional 5898 new ID PMTs Ready by April 2007

As of April 1

Resurrection

16Next steps

Tau appearance

+ N - + X

Oscillation patternDip in L/E distribution

P( ) = 1 - cos4sin22 sin2(1.27m232L/E)

　　　　　　　　　 - P( e) P(e) = sin22 sin2 sin2(1.27m13

2L/E)

70 yr Monte Carlom2=2.5×10-3eV2

17K2K long baseline neutrino oscillation experiment

5.6×1019 pot (June 1999 – July 2001)

250 km

18

Best fit 1R spectrum & Nsk

Best fit point (sin2223 , m232) 　 =

(1.0, 2.8x10-3eV2) KS test prob.(shape): 79% NSK=54 (Obs.=56) Very good agreement in shape & NSK wit

h atmospheric neutrinos

Expected w/o oscillationNormalized w/o oscillationNormalized with best fit oscillation

Total number of obs. Events: 56 16 (Jan03-Apr03)

Expected w/o oscillation: 80.6 +7.3-8.0 24 +2.3-2.1

19T2K (Tokai-to-Kamioka)

J-PARCHyper-Kamiokande

20

JHF MINOS K2K

E(GeV) 50 120 12

Int.(1012ppp) 330 40 6

Rate(Hz) 0.29 0.53 0.45

Power(MW)

Phase-II

0.77

4

0.41 0.0052

50 GeV JHF PS 2007

Kamioka

21Expected sensitivities (5yrs)

0.01

1×10-4

True m232 (eV2)

(sin22) ~ 0.01 (m2) ~ <1×10-4

OAB-2degree

disappearance

w/ beam MC, & full SK det. simulation

(si

n2 2

)(

m23

2 )

excludedby reactor

132

2322 2sinsin2sin e

~0.5sin2213>0.006 (90%)sin2213>0.018 (3)

x20

Sensitivityin 5 years

NBB 1.5GeV

NBB 3 GeV

e appearance

22Hyper-Kamiokande (1Mt water)

Precision neutrino oscillation study Proton decay search

R&D (complete in 2 years) Cavity excavation and its stability New light detector: Hybrid Photo-

Detector, HPD (50cm)

23

Thank you

24Oscillation Among 3 Flavors

P(e) = sin22 sin2 sin2(1.27m132L/E)

P( ) = 1 - cos4sin22 sin2(1.27m232L/E) - P( e)

sin213 < 0.1, cos413~1 (from the CHOOZ experiment)

sin22 ~ sin2223 ~ 1,sin22e = sin2213 sin223 ~ 0.5 sin2213 ~ 2|Ue3|2

m3

m2

m1

m3 >> m2 > m1