1

ニュートリノ物理発展と動向 ２００２年１月１６日

＠国際高等研究所京都大学大学院理学研究科

西川公一郎

1. What do we know today?

• Solar Neutrino results (SK & SNO)

– First direct observation of oscillation 　 in solar

• Atmospheric neutrino results

– Atmospheric deficiency

• LSND and KARMEN

• More than 3 neutrinos?

• Present status of K2K

2. What should be (shall be) done next

3. Conclusion

2

3 Generations MNS matrix

• 3 angles and 1 phase

e2i

3

2

1

321

321

3e2e1ee

E2

m

UUU

UUU

UUU

2323

2323i

13i

13

1313

1212

1212

cossin0

sincos0

001

ecos0esin

010

sin0cos

100

0cossin

0sincos

U

propagation

23223

213

24212 eV10m)m()eV10(m

solar e : m2 <10-4eV2 　　　　　　　　　 no

reactor e : (Chooze, Pal-Verde) Ue3 ~ small

atm. m2 >10-3eV2 and

3

Measurements at m2>10-3eV2 (L/E ~ several 100 (km/GeV))

m223~m2

13>>m212

E

Lmsin2sincos

2232

232

134

E

Lmsin2sincos

2232

132

232

e

E

Lmsin2sin1

2232

132

ee

Three generation ?mixing anglemass difference

4

Solar neutrinoe =

1. Standard Solar Model (SSM) and experiments

2. New SNO results

3. Super-Kamiokande update to 1286 days

4. Summary of the status

5

Sources of Solar Neutrinos

http://www.sns.ias.edu/~jnb/

SNO

Each experiment　 is seeing different sources

Standard Solar Model relates different kinds of experiments

Target Data / SSM(BP2000)

・ Homestake 37Cl 0.32±0.03

・ Kamiokande e- (water) 0.54±0.07

・ SAGE 71Ga 0.58±0.06

・ GALLEX+GNO 71Ga 0.57±0.05

・ SK e- (water) 0.465±0.015

74 ±775 +8-7

GaH2O37Cl SuperK Kamioka SAGE GALLEX(+GNO)

0.47±0.020.54±0.07

Homestake

2.56 ±0.23

8.1 +1.4-1.1 SNU 129 +9

-7 SNU1.0

Theory7Be8B

pp, pepCNO

Experiments

+0.20-0.16

Be 0

B 0.5

then….no need of osc.

Solar Neutrino Experiments (as of 2000)

7

8

Measurement of 8B (SK and SNO)

• SK e + e e + e CC : NC =6:1 (1)– forward peaked

• SNO e + d e + p + p CC (2)

　　　　　　 e + e e + e CC : NC =6:1•(1)-(2) NC event rate due to 8B

•should be constant for oscillation among active neutrinos

–8B Flux measurement with neutral current interaction

•Confirm SSM (Be, B pp chain = solar 　 luminescence)

•Flux (deduced from NC) – Flux (deduced from CC)

= Non e components

•SSM independent evidence of oscillation

9

New SNO results• Teff=6.75 Mev

• No large spectrum distortion

• Charged current :

　　 ( Q=1.44MeV)

e + D p + p + e (CC)

• electron scattering :

+ e e + (ES)

12612.0

01.0scm10)07.075.1(

12616.0

14.0scm10)34.039.2(

10

SK

CC = e

ES = e +0.154 ,

SNO CC = 1.750.15SK ES = 2.320.09

, = 3.691.13

X = 5.440.99 (total active 8B neutrino flux)(SSM = 5.05+1.01/-0.81)

[x106/cm2/s]

SK + SNO combined

11

Super KamiokandeSuper Kamiokande

41.4m

39.3m

50kton stainless steel tank

Outer detector 1867 of 8” PMT

Inner detector11146 of 20” PMT

Ikeno-yamaKamioka, Gifu

Mozumi Atotsu

3km 2km

1km(2700mwe)

12

May 31, 1996 - Oct.6, 2000 1258 days

e-

sun

COSsun

Ee = 5.0 - 20 MeV

~18500 solar events

(14.7 events/day)

+0.016-0.013

8B flux : 2.32 0.03 [x 106 /cm2/sec] Data

SSM(BP2000) = 0.451 0.005

+0.08-0.07

(using Ortiz et al. spectrum shape(nucl-ex/0003006))

Direction to the Sun

13

e→()

99% C.L.

Oscillation parameters based on flux of Homestake, GALLEX, SAGE and SK

122

2

12212

122

m12

2

2sin2cosm

EV2

2sin2sin

VE2

m2cosV

21212

c

e

c

only e has e CC

14

Small Mixing angle solution

Seasonal effect, spectral distortion

P( e

→

e)

Large Mixing solution

Low

Just-so

solar neutrino spectrum

Day

Night

Spectral shape distortion

Day/night difference

oscillation in solar neutrino

Day/night in pp

Day/night, spectrum with higher precision

15

Earth density: =5g/cm2 (average),13(at core) Affect to oscillations for m2 = 10-6 - 10-4 eV2

(Night-Day)

(Night+Day)/2

e

1%2%

10%

80%

slight negative

Day/Night Effectregeneration through the earth

N-D = 0.033 0.022(stat.) (N+D)/2

0.0130.012 (sys.)

16

(6.310-3, 510-6eV2) SMA

(0.75, 6.310-11eV2) Justso

(0.8, 3.210-5eV2) LMA

Bad fit for SMA and Just-so solutions.

Spectrum shape comparison

uncertainties of absolute energy scale, energy resolution, 8B spectrum shape

17

Excluded by SK zenith angle spectrum at 95%C.L.Allowed by global fit (Cl + Ga + SK flux) at 95%C.L.

95%CL

m2(e

V2)

sin22

e e sterile

. e

2. LMA prefered

18Fogli et.al. hep-ph/0106247

19

2 for eccentricity: 3.9 / 7 d.o.f. (79% C.L.)

2 for flat: 8.1 / 7 d.o.f. (32% C.L.) )

Sunspot #

Time variation of the flux, seasonal

No magnetic field dep.No distance dep. (Just-so)

20

Kamioka Liquid scintillator Anti-Neutrino Detector

http://www.awa.tohoku.ac.jp/KamLANDKamLANDKamLAND

1000m3 liquid scintillator3000m3 oil+water shield1300 17-inch PMTs +600 20-inch PMTsAnti-e from reactors (L~170km)Detect e+ from e + p e+ + n (Eth = 1.8 MeV)

21

From K.Inoue (Tohoku Univ.)

KamLAND: sensitivityKamLAND: sensitivityWhat(3)

22

Conclusion on solar neutrinos

• There is non-electron neutrinos in solar neutrino oscillation!• SSM is OK within 20%• Just-so, LOW, and SMA are disfavored

– 93 % C.L. by SK zenith-spectrum analysis for e→ oscillations.

• Sterile is disfavored with 95% C.L. by zenith-spectrum.

• Energy spectrum is consistent with flat.

• day/night difference is 3.3±2.2 +1.3/-1.2 %.

• Large angle solution : testable in KAMLAND• Also by Borexino

23

Interaction in the rock

FC + PC

through-going muons

stopping muons

Initial neutrino energy spectrum

FC

Through-going muons

Stopping muons

Event topologyPC

24

Zenith angle distribution (Soudan 2)

cos log(L/E)

HiRes events (106.3±14.7 nm, 132.8±13.4 ne)

Decay excluded by 2

25

Zenith angle distribution

No oscillation

Δm2=2.5x10-3

sin22θ=1.0(best fit)

26

allowed region

FC + PC + up-through +up-stop +Multi-ring

χ2min=142.1/152dof

@(Δm2,sin22θ)=(2.5x10-3,1.0)

27

v.s. s

　　　　 C.C. N.C. X ○s 　　　 　 X 　　 X 　

•NC in the earth ( matter effect ) PC, up through μ(high energy) FC (low energy)

CC interaction in SK detector appearance

28

matter effect in the earthsin22θm =

sin22θ( -cos2θ)2+sin22θ2VEν

Δm2

sin22θ～ 1, Eν>20GeV sin22θm 1≪

PC, Evis>5GeV<Eν> ～ 25GeVup/down ratio

up through going μ<Eν>～ 100GeVvertical/horizontal ratio

νμ ー ντ

νμ ー νs

νμ ー νs

νμ ー ντ

29

v.s. s

high energy PC up/down ratio

up through μ vertical/horizontal ratio

NC enrigh multi ringevent up/down ratio

νμ ー νs

νμ ー ντ

νμ ー ντνμ ー ντ

νμ ー νs

νμ ー νsdata

30

ντ + N → τ + N’ +π+π..., e, +hadrons(,....)

appearance study

CC interaction

Many hadrons are produced.

Optimized by using onlydownward going events.

compare upward going data and MC.

enriched sample

νμ-ντ

with ντCC

νμ-ντ

w/o ντCC

# of obs. τ efficiency# of τ (eff. corrected)

43±1742%103±41

+8- 11

+18- 26

• ～ 2σ excess of τ-like events.• Data are consistent with νμ-ντ oscillation with ντCC.

31

Summary of atmospheric neutrino observation

• Oscillation parameters for : m2 = 1.6 ~ 3.6 x 10-3 eV2, sin22 > 0.90 (90%CL)

• Decay scenario is disfavored with > 2for dcy>>osc and dcy<<osc

s is strongly disfavored

• Excess from leptons: 1.5 ~ 2• Future

– Implement 3D flux calculations

– Study more on -lepton production

– Study on the mixed final state +s

32

LSND and KARMEN

Stopping onlydecayabsorbed in nuclei

componentno

,,

e

e

e+p→e++n n+A→A’+

33

LSND-Karmen-Nomad comparison

Small m2

region remains

34

35

mass - oscillationsallowed regions

LSND, if true, more than 3 neutrinos ?No sign in solar and atmospheric neutrino obs.

36

K2K( Testing atmospheric observation with accelerator neutrino beam)

• Distance and direction fixed

neutrino energy (E• Neutrino beam just after birth• 99% decay volume)

)E

Lm27.1(sin2sin.prob

222

L=250km

37

Bird’s Eye Neutrino Beam Line

38

Spectrum Distortion at Off axis(4 mrad) (MC)

1 06

1 07

1 08

1 09

0 1 2 3 4 5P (G e V /c )

O n a x i s f l u x

O f f a x i s f l u x

mradian accuracy is more than enough

39

stability monitor

２００ｍ１ｃｈ＝５ｃ

ｍ　　＝０．２

５ mrad.

<1mrad.

-1mrad.

+1mrad.

40

Near neutrino detector

Fine Grained Detector

300m from target

41

Neutrino Beam Direction　 (MRD　 profile)

Fitted centerx: 1±5cmy: － 10±4cmCentered within sys. err. of 20cm

SK direction(0.7mrad).

x, x

標的

near det.

300m

400cm

42

Stability of Spectrum

Muon Energy of MRD events

Muon Energy of 1kton events

43

K2K Results(June ‘99 – July ‘01)

1. Number of events• 1 kton water Chrenkov detector

SK almost counting experiment

– NC/CC, spectrum shape, interaction model

errors almost cancell

2. Spectrum distortion• non-QE , NC must be subtracted

44

SK EventsTspill TSK

GPS

No Decay-eHE Trig.Evis cut (30MeV)

No act. in OD(fully contained)

Exp’edAtm BG <10-3 in1.5s window

56 in fid. vol.

-0.2<TSK-TSpill-TOF<1.3sec

TOF~1msec

1sec

45

Dominant Systematic Errors •uncertainty of far-near ratio (~7%) and •uncertainty of 1kt fiducial volume (~4%).

46

Reconstructed E and muon directionFully contained 1-ring -like (22.5kt)

Need to estimate syst. err. Note: m2=310-3 eV2 corresponds to 600 MeV E

MC w/o osc.

47

Summary of K2K• Accumulated 4.5x1019POT @ SK from Jun ’99 to July

’01. (1.0 1020 protons in 2004)

• Neutrino beam is well under control Can extrapolate spectrum and flux from Near to Far

• # of fully contained events in fiducial volume @ SKObserved: 56, Expected with null oscillation 80

Probability of null oscillation < 3%

• Spectrum analysis, especially improving low energy region, just started– Pion production measurements @ CERN (HARP)– Upgrade in summer 2003

+7.3-8.0

48

• Atmospheric neutrinos– Where ( m2 =1.6·10-3 ~ 4·10-3 eV2 , sin22.– Most likely

• Solar neutrinos– LMA likely Large 12 ,m2

12 ~10-5 : CPV asym. can be large

• Reactor neutrinos– sin2213<0.1 for atmospheric m2 region

• K2K – Decrease over 250km of ~1GeV neutrino– Spectrum distortion

• Minos, MiniBooNE, CGN, Kamland– Oscillation pattern, appearance, LSND, LMA

• What is the best bet for the next step ?

49

Final goal (my own view)• Our own existence ?

– (near) GUTs scale physics• Mass-Interaction : mixing (or

?)• Small neutrino mass

– Existence of CP-violation in lepton sector (lepto-genesis)

– Baryon number non-conservation• Very massive detector

50

• CPV in Kaon system was discovered just below Adair’s measurement

• CP phase is large in K,B (Jarlskog factor is small)

• No theorist predicted large mixing 23

• No strict prediction on 13 , • 14 order of magnitude extrapolation for proton dec

ay prediction

• One order of magnitude improvements are worth the effort !

• Major discoveries may be around the corner

51

CP Violation in Lepton Sector (Why e)

=0 for appearance exp!

e

Current limit

E2

L)mm(sin)UUUUIm(2

E4

L)mm(sin)UUUURe(4P

2i

2j

ij

*jji

*i

2i

2j2*

jjiij

*i

52

CP Violation(difference of particle and anti-particle)

sinsin

2sin

E

Lm

PP

PPA

13

12212

CP

Solar 10-4~10-5 eV2 0.8 for LMA

Reactor experiments (CHOOZ)ex at atmospheric m2 region<0.16

remain to be discovered) : first step : second step

E

Lmsin2sincos

2232

132

232

e

53

Precision second generation experiment

CP violation measurementOscillation pattern , , m2

Sub-GeV Beam + Large water Cherenkov detector Beam control-ability and stability Event reconstruction (single e, ) Energy reconstruction Event selection (GPS timing)

Meaurements = (E) x Flux(E) x Detector responseSystematic studies of (anti-v) interactionsDetector response

Near/Far extrapolation

54

sin2213 from appearance experiment e + n e + p

sin2213

Background in Super-K (as of Oct 25, 2001)

SignalSignal + BG e e total

0.1 12.0 10.7 1.7 0.5 24.9 114.6 139.5

0.01 12.0 10.7 1.7 0.5 24.9 11.5 36.4

0.5 sin2213

m2

Off axis 2 deg, 5 years

Off axis 2 deg, 5 years

Wor

k in

pro

gres

s

55

Schematic drawing of Hyper-Kamiokande

1 Mton (fiducial) volume: Total Length 400m (8 compartments)

56

Sensitivity(3)

Chooz excluded@m31~3x10-3eV2

JHFSK cannot discover 13

IF BG sys 2%

sin2213=0.01sin>0.55 (33deg)

large sin2213

sin>0.25 (14deg)

Study in progress !

57

Artificial Neutrino Sources

• Conventional neutrino beams

• Neutrino factory – Very small backgrounds– Continuous Spectrum

N,

N,

e

e

,NP ee100

58

J.Wilkes’ TableExperiment

Property

SK K2K MINOS ICARUS OPERA JHF-Kam MONOLITH

-factory

CNGS

(m223)

±%

50 20 10 10 20 3.3 6 2

(sin22 23)

±%

5 5 5 5 ? 1 4 2

Osc peak X? ○* ○? X(○atm) ? ○ ○ ○

appear-

ance

○? X ○ ○ ○ X ○ ○

sin2213 >0.1 >0.01 0.03 0.015 ? 0.006 ? 1~3x10-3

(s/) 0.2 X 0.05? 0.05 ? 0.2? ~0.2 0.01

decay ○? ~X ○ X(○atm) ? ○ ○ ○

Sign of m2 X X X X X X X ○

CP violation X X X X X ○ X ○

On-going experiments

(www.phys.washington.edu./~wilkes/NNO/)

59

Solar Neutrinos8B NC is consistent with SSMNon-e neutrino in solar neutrino flux Sterile disfavoredCl, Ga, SK flux and 8B spectrum, Day/Night almost eliminate SMA, LOW solution

Spectrum , Day/Night , NC high precision measurementsLong baseline reactor exp. test LMA solution (Kamland)Solar neutrino at low energy (Borexino, Xmass….)

Atmospheric Neutrinos1.6x10-3 <m2 < 4x10-3eV2 sin22 > 0.89 (90%C.L.)s oscillation is disfavored with 99%C.L.-enrich data is consistent with t oscillation with CC.

Still Statistics limited

Conclusion-1

•

60

Conclusion-2

Accelerator experiments K2K 97% CL energy distortion in a few years, if m2>2x10-3eV2 KARMEN/NOMAD eliminate m2>eV2 region of LSND

Sterile? (Mini-BooNE) Direct confirmation of OPERA, ICARUS

Dip in disappearance ?m232 (JHFSK,MINOS)

e appearance ( JHFSK) CP violation in lepton sector (JHF-HyperK)

0Majorana neutrino!