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Junpei ShiraiResearch Center for Neutrino Science

Tohoku University

(for the KamLAND Collaboration)

Neutrino experiments: Review of Recent Results

Tau04, 8th International Workshop on Tau-Lepton Physics,Nara, Sept.16, 2004.

Contents:

Neutrino Oscillation Experiments

Solar and Reactor Neutrino Results

Atmospheric Neutrino Experiments

Coming experiments

Double beta decay &

Search for neutrino mass

Summary

Neutrino Oscillation Experiments:

Long history (40~50years!) of challenging mass!

Survival probability of :

1sin22sin2 ( ) <1 ?Mij2LL

4E[Source] [Detector]

ij

coscossinsin

=

dE

Solar : SNOReactor : KamLANDAtmospheric : SuperKAccelerator : K2K

Clear evidence of -flavor change;Flavor change of occursdominantly by Oscillation.

does have a Mass!

Mij2=Mi

2 -Mj2)

Oscillation parameters determined by

P()=1 P()

Flavor eigenstates Mass

eigenstates

* Tiny , M=0 (SM)

Solar Neutrino Problem (SNP)

e

e ?[Earth]

4p+2e4He+2e+26.73MeVE

(Pure e flux is generated by thermo-nuclear fusion in the center of the sun!)

flux: Observation < Prediction[SSM][Experiments]

[Sun]

ppde pepd

pdHe

He HHe 2p

He HBe

He pHe e+

Neutrino generation & spectrum [SSM]

Be eLi

Li p2He

Be pB

BBe* e+ 24He

pp ( .909)

7Be () 8B ()

pp-chain(98.4%) +CNOcycle(1.4%)

J.N.Bahcall

Flu

x@1A

U(/

cm2 /

s/M

eV),

(/c

m2 /

s fo

r li

nes

)

pep ()

hep()

Kamio-kande, SuperKSNO

8B only7Be &above

pp &above

Establish Solar- deficit

‘60

‘70

‘80

‘90

‘00

Homestake

Kamiokande

SuperK

Solar experiments

+e+e

+e+e

[H2O]

[H2O]

e+71Ga71Ge+eGallex/ SAGE

‘83~’96

‘96~

e+dp+p+e+d n+p+N+e+e [D2O]

obs/[SSM]

0.5‘68~

‘90~’01‘91~’97

SNO ‘99~

RadiochemicalReal time

(PDG’04)

0.40.3 0.6

GNO

e only

e++

e+37Cl37Ar+e[C2Cl4]

First observationof solar

really comes from the sun

Detection of pp

High Precision measurement

Active Non-e Components !

PRL 89, 011301(‘02) First evidence of Active Non-e component.

Clear deficit of e): Excellent agreement with SSM.

Oscillation looks very promising, but several solutions of M2 and for SNP!

e+dp+p+e

+d n+p+

+e+eSNO

SSM=5.05+1.010.81e)=1.76±0.06(stat) ±0.09(sys)

=5.09+0.44 (stat)+0.46

(sys)0.43 0.43

(106cm2s)

CC /NC= e(e++ )

CC /ES= e[e+0.154(+ )]

n+d H+(6.25MeV); 0.5mb (~’01)n+Cl Cl+’s(8.6MeV); 44b (~’03)n+He p+H; 5330b, event/event (’04~)

Neutron detection ;

(106cm2s)

-Oscillation parametersFour solutions to SNP

VAC(just so)

Matter effect (MSW effect)

P(ee)=1sin22sin2(M2L/4E)

M2sin22 22EGFNe cos2

sin22

SMA, LMA, LOW by

LMA looks very promising, but no single experiment uniquely determined the solution.

Needs decisive experiment !

H.MurayamaAllowed region(95%)

Seasonal variation, D/N asymmetry, Energy Spectrum ;

e only]

Man-made provided by Reactor.

Reactor neutrino experimentsLong history since the first detection of neutrino by F.Reines and C.L.Cowan using a reactor in 1950s.

n

n

AX

Y

Neutron rich nuclei to decay.

e emission

Power reactorsas a source.

+ ~200MeV/fission

235U, 239Pu,241Pu, 238U

Typical reactor : 3GW(thermal energy) !

Pure and intense flux which is known < 2% !Measure P(ee) with a distant detector.

Previous reactor results

Intense e source & Large Detector are crucial! KamLAND

No oscillation was found!

EdM2>10 eV2

M2~105eV2 to check LMA,Loscil= M2

(epe+n)

e interactions

e flux

E(MeV)

e spectrum of each fuel elementis experimentally known or calculated (~2%).

2E ~O(100)km

Threshold(1.8MeV)

e flux, and interaction energies

6 84 5 73

KamLAND Experimental Area

2.2km

1000m SuperK

Nitrogen Gas System

Control RoomDetector

Oil Purification System

Water Supply System

Kamioka mine

~70GW(thermal) within175±35km from KamLAND.7% of the total reactor power in the world !

2700m w.e.~0.3 ’s/sec

1000ton Ultra pure LSin a 13m Balloon

KamLAND Detector

PMTs (in 2.5m thickmineral oil;1325 17”(t~1.5ns)+554 20”() E/E~7.3%/E[MeV]

Water Cherenkov counter(225 20”PMTs)

~106 e/cm2/sec @KamLAND

KamLAND

52 power reactors in Japan

(E>1.8MeV)

(Kamioka Liquid scintillator Anti-Neutrino Detector)

20m

235U

239Pu

238U241Pu

Reactor Neutrino flux at KamLANDThermal Power

Burnup

Typical reactor operation

1106 e/cm2/sec (E>1.8MeV)

Wakasa Bay

KashiwazakiOthers

HamaokaShika

Korea

Total

is precisely estimated within ±3.4%

Fission rates are calculatedby thermal power and initial fuel composition.

Fission Rates

Reactor power 2.1%, Fuel comp.1.0%-spectra 2.5%

Mar’02Jan’04

e Detection:Traditional method since F.Reines used Liquid Scintillator as an active target !

e

pe+ e

n

p

d

(0.51)

(0.51)

(2.2)

[Prompt e+ signal]

[Delayed by neutron capture]Correlated signals;

(Energy, Position, Time)

Greatly removes backgrounds!

[E1.8MeV]

e; ID, E, time, position

Ee+(=E0.8MeV)

eeeerecisely known (0.2%)

~200s

epe+n

KamLAND:Vertex and Energy Calibration

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-ray sources along the central z-axis

12B/12N68Ge,60Co,65Zn

n pn12C

Off axis by-spallation

±2%

±5cm

E/E

Fid vol.(R<5.5m)

Z-position

Z--

devi

atio

n(cm

)

(R/6.5m)3

12B/12N(4~15MeV)

(Nfid/Ntot)/(Vfid/Vtot)Total vol.Energy dependence

Fiducial

Fiducial vol. Error = 4.7%Energy threshold(2.6MeVPrompt signal) = 2.3%

KamLAND: Event Selection

Correlated events :

0.5s<T<1msR<2mEdelay=1.8~2.6MeVEprompt-e+=2.6~8.5MeV

Reject geo-

Time, Distance &Energy of Delayed events

Fiducial cut: R[prompt], R[delayed]<5.5mReject -spallation (9Li/8He rejection): 3m cylinder from the Whole detector

Prompt event

Delayed event

New Analysis!* Data sample:766.3 ton yr (Mar.9,‘02~Jan.11,‘04)4.7 times larger statistics than the 1st results

RFid=5.5mRBalloon=6.5m

[showering [non-showering ]

9Li/8He bkg: 4.8±0.9 events

Results

2.6MeV

Observed e : 258Expected for non-oscillation : 365±24Background : 7.5±1.3

9Li/8He: 4.8±0.9Fast neutrons: <0.89Accidental: 2.69±0.02

[>2.6MeV]

analysis region

sin22 = 0.83m2 = 8.3×10-5 eV2

Best-fit oscillation parameters

2.6MeV

(Nobs-Nbkg) NExpected

= 0.686±0.044±0.045(stat) (sys)

Clear disappearanceat 99.995%CL

Scaled No-oscillationExcluded at 99.9%CL

Combined : 99.99996%

Null Oscillation Hypothesis disfavored

2.6MeV

(Nobs-Nbkg) NExpected

= 0.686±0.044±0.045(stat) (sys)

Clear disappearanceat 99.995%CL

Observed e : 258Expected for non-oscillation : 365±24Background : 7.5±1.3

9Li/8He: 4.8±0.9Fast neutrons: <0.89Accidental: 2.69±0.02

[>2.6MeV]

No-oscillationResults

L/E plot to check Oscillation or other hypotheses

Decay : cos2+sin2exp[mL/(2E)]Decoherence : 1(1/2)sin2 2exp[L/E]

Excluded at

96.5%

98.3%Neutrino Oscillation isthe best to fit the data!!

Excluded at

Barger et al.,PRL82,(‘99) 2640

E.Lisi et al.,PRL85,(‘00) 1166

Best Fit Oscillation

Oscillation Analysis with 2 flavors

Solar LMA

Best fit (in LMA1)sin22=0.83m2=8.3105

New results

1st results

Best fitsin22=1.0m2=6.9105

PRL 90, 021802(2003)

LMA2: excluded at 99.6%CL

LMA0: excluded at 94%CL

210Pb210Bi210Po +13C n+16O*(6.13, 6.05)22.3y 138d

222Rn

5d206Pb (stable)

5.4MeVprompt delayed

3.8d

A New Background source (,n) !

n+12C 12C*(4.4) +n npd

Excluded(95%)

Excluded(95%)

LMA

Possible background sources;(,n), spontaneous fission of 238U,NC reaction by atmospheric ,NC reaction by solar on deuterons

Global Analysis of KamLAND+ Solar

Mass difference

tan2=0.40+0.09

m2=8.2+0.62eV2

Mixing angle

Preliminary

New 13C(,n)16OBackground ~10events

KamLAND has shown decisively oscillation of LMA and M2 has been measured very precisely!!

2004)

SK Atmospheric neutrino oscillation

Zenith angle distributionSK-I (1496days; 1996-2001):

e-like -like -like

Up-goingstopping

through

cos

cos

cos

cos

Up Down

Oscillation explains quite wl !Strongly disfavored null oscillation!

E.Kearns(2004)

Best-fit & Contours

SuperK L/E AnalysisSelect events with best L/E resolutionTo observe oscillation pattern!

2726 events by a cutof 70% resolution

decay decoherence

Decay rejected at 3.4 Decoherence rejected at 3.8

SK-1 L/E Analysis

SK-1 All Data

K2K

oscillation, dip at ~500km/GeV

Further constraint on m2

m2=(1.9~3.0)103eV2

sin22>0.90 at 90%CL

Best fit: (sin22m2)=(1.02, 2.4 103eV2 ), 2=37.7/40 dof

Other L/E resolutionDifferent binning of L/EChange of the direction vectorE-like event

Dip: checked by

13 and CP in lepton sector

e

3 mixing angles; 12, 23, 13

Three Mass differences; M213~M2

23>>M212

CP-violating phase

Atmospheric K2K

New challenge !!

Reactor Solar

cij=cosij

sij=sinij

Reactor and LBL-Accelerator approaches are complementary!

* Present limit: sin2213<0.12(CHOOZ)

e

c23

s23s23

c23

1 0 0

00

c13

0s13ei

c1210 s13e-i

00c13

0s12

1

0s12

00

c12

=1

PMNS-matrix

Reactor & LBL-accelerator experiments.

Reactor : P(ee)

c134sin2212sin212 s12

2sin2213sin232 c122sin2213sin231

ij(Mi

2Mj2)L

4E

Reactor , L~O(1)km

P(ee)=1 sin2213

to make sin232,

Accelerator : P(e)= sin2213sin223sin232

~1 (taking L~2E/M322)

2 M23

2

M122

cos13sin212sin223sin213sin

cij=cosij , sij=sinij

[Pure 13 measurement !]

~0.04

LBL & Reactor

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0 0.02 0.04 0.06 0.08 0.1 0.12 0.140

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14

Reactor Measurement

LBL-Accelerator.Measurement

sin2213

P(

e

)

sin223={1±1-sin2223}/2

Intrinsic uncertainty from sin223

0.390.61

sin213sin

LBL-accelerator experiment alone;

and sinambiguity to determine sin2213

Reactor 13 measurement solves them. sin2213 provides the observability of the .

ex) sin2223 =0.95 (Lower lim. SK) sin223 =0.61, 0.39

7 reactors

2 Near detector

Far detector

Kashiwazaki Nuclear Power Plant (Japan);24.3GW(World’sLargest thermal power!)

~400m

1300~1800m

0

1

2

3

4

5

6

-1

-2

-3

-4

7p

LS

Gd-LS(8.5ton)

6m

Gd-LSepe+n

promptDelayed(~30s)

’s~8MeV(Gd)

[Detector]Depth: 200m(far), 70m(near)

Non-Gd LSSys. Error 0.5~1%(<1%(det)+ 0.2%(flux))

Sensitivity: sin2213~0.017-0.026

40,000events/2yr (Far det.)

Buffer oil

Kaska: Reactor 13 measurement

Search for decays

e e

W W

A(Z) A(Z+2)+2e +2e (L=2)

Majorana

(T)=G|M|2 |<m>|2

Nuclear Matrix element

Phase space factor

|<m>|=|Uei2mi|=|m1c12

2c132+m2s12

2c132e2i +m3s13

2c132e2i|

3

i=1

It is related to the neutrino mass scale.Mass hierarchy; m1m2m3 [NH], m1m2m3 [IH], m1m2m3 [QD]

is very important. If found, L=2 process, Majorana neutrino, |<m>|constrains neutrino mass patterns !!

Effective Majorana mass

A(Z) A(Z+2)

Nuclear process

cij =cosij, sij =sinij

Majorana CP phase

1Sensitivity of

would make a breakthrough !

|<m>| & mass hierarchyE

ffec

tive

mas

s |<

m

>| (

eV)

0.01

0.10

1.00

0.001

1.000.100.0100.001Minimum neutrino mass (eV)

PDG’04

Degenerate

Inverted Hierarchy

Normal Hierarchy

Mass pattern and minimum mass

sin2solm2sol~5meV

m2atm~50meV

m1~m2~m3

m1~m2>m3

m1~m2<m3

|<m>|=|m1c122+m2s12

2e2i

+m3s132c13

2e2i|

0

|<m>| > a few10meV Inverted hierarchy

appears as a sharp peak at the highest energy of the 2 spectrum in decays.

Sensitivity (Lower limit of T1/2[y])

BM t E

# of nuclei=(M/A)NAa

Background rate; counts/kg/KeV/yEnergy resolution;KeV

[BG][Signal]

A; atomic weight, a; AbundanceM; Total mass [kg]

T1/2 A

a M tBE

running time; y

|<m>|=[T

1/2G|M|2]1/2

1

Q5

Detection efficiency

(T1/2 /ln2)

N t

Key for Search

Lots of Challenges to 0

Scintillation

CryogenicsCUORE/CUORETINOCOBRAGEMGENIUSMajoranaMPI

CAMEOCANDLESCARVELGSOXe

DCBAMOONNEMOEXO

Tracking

113Cd, 123Te

76Ge116Cd

48Ca116Cd

160Gd136Xe

150Nd100Mo

82Se136Xe

Crystals in Liq. Scint.

Foils in wire chamber,TPC, Mag. fieldIonization (LN2)

Bolometory

a MBE , Q

Making large figure of merit

to reach |<m>|~100-10 meVin several years operation!

Direct mass measurement

Use only kinematics of decay particles to measure missing mass. (cf. -oscillation, , astrophysics)The fact of large flavor-mixing of Properties of ’s (incl. mass) might be the same. Mass degeneracy can be checked with a sensitivity of sub-eV.

Tritium -decay has been tried : Small endpoint energy (18.6keV) Super-allowed transition Final state spectrum of daughter molecules are well known.

Troitsk m<2.05eV(@ 95%CL)Mainz m<2.2eV (@ 95%CL) PLB460(‘99)219.

PLB350(‘95)263.

m=0

m0

E0-Ee E0

dN/dEe=KF(Ee,Z)peEtot(E0-Ee)[(E0Ee)2m2)]2

Both uses magnetic-bottle spectrometer and gaseous 3H target.

dN/d

E

KATRIN (Karlsruhe Tritium NeutrinoExperiment)

Electrostatic spectrometer with Adiabatic magnetic collimationWindowless gaseous tritium source

Large acceptance, High resolution

=Etrans/B : conserved in adiabatic B fieldE/E=Banal/Bmax : Energy resolution (Banal ~a few mT, Bmax~6T)

~70 m beamline, 40 s.c. solenoids

Stainless steel vessel(10m

-mass sensitivity: 0.2eV

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Needs confirmation by coming experiments!

Degenerate!

Highest Sensitivity,Select single site events by PSA

(H.V.Klapdor-Kleingrothaus,2004)

A claim for discovery of

Can be found by direct measurement with sub-eV sensitivity and planned 0 experiments!

SummaryRecent experiments have established oscillation by observing the flux deficit, flavor change and spectral distortion; Solar (SK/SNO)/Reactor (KamLAND) for e (e), Atmospheric (SK)/Accelerator (K2K) for

Oscillation parameters, 12, 23, M122, M 23

2 are being determined precisely by ongoing experiments.

Reactor 13 measurement is very important to the coming LBL experiment aiming to measure CP-violating phase

experiment is crucial not only to know whether , but constrain or determine mass pattern, if |<m>| sensitivity to ~0.01eV is attained.remass search with a mass sensitivity of sub-eV can havea discovery potential.

Backup slides

M0

Solar problemAtmospheric anomaly

oscillation !

Absolute mass?Mass pattern?CP & Mixing mechanism?

Precise measurement ofoscillation parameters.Planned , LBL experiments

1000ton D2O in 12m acrylic vessel9600 PMTs (60%of 4)

H2O (1700ton inner shield +5300ton outer shield)

Deep underground 6010m w.e.

Urylon Liner and Radon Seal

Sudbury Neutrino Observatory