Neutrino Oscillations: experimental triumphs, remaining ... · Neutrino Oscillations: experimental triumphs, remaining puzzles ... SAGE (Baksan, Russia), Gallex and GNO (Gran Sasso,

Neutrino Oscillations:Neutrino Oscillations:experimental triumphs,experimental triumphs,remaining puzzlesremaining puzzles

Giorgio GrattaPhysics Department, Stanford

SSI 2004 Experimental Neutrino Oscillations - Gratta 2

What we do know: What we do know: -- Status of neutrino mixingStatus of neutrino mixing

How did we learn it: How did we learn it: -- Solar neutrinoSolar neutrino-- Atmospheric neutrinoAtmospheric neutrino-- Reactor neutrinosReactor neutrinos-- K2KK2K

Addressing remaining puzzles in neutrino mixing:Addressing remaining puzzles in neutrino mixing:-- LNSD/LNSD/miniBooneminiBoone see Sam Zellersee Sam Zeller-- θθ13 13 experimentsexperiments-- Hierarchy/CP violation: Hierarchy/CP violation: νν--fact/fact/ββ--beamsbeams-- Absolute m, Absolute m, Majorana/DiracMajorana/Dirac νν

see Steve Elliottsee Steve Elliott

Impossible to be complete: I will just make an arbitraryImpossible to be complete: I will just make an arbitrary--and hopefully interestingand hopefully interesting-- selectionselection


If mIf mνν≠≠0 then the 0 then the 3 weak3 weak--interactions interactions eigenstateseigenstatescan be represented as superposition of mass can be represented as superposition of mass eigenstateseigenstates

jν

∑=j

ljlj U νν

jljj l

LEmiljl

LEmi

lljj UeUeU ll

′′′

−− ∑∑∑ ≅≅ ννν *)2/()2/( 22

Neutrinos are produced and detected by weak interactionNeutrinos are produced and detected by weak interactionbut propagate in vacuum as mass but propagate in vacuum as mass eigenstateseigenstates……

From LEP and SLC we know that there are2.981±0.008 active, light ν flavors

We also know that 3 ν flavors were active inBig Bang Nucleosynthesis

Neutrino oscillations


⎟⎟⎟

⎠

⎞

⎜⎜⎜

⎝

⎛•

⎟⎟⎟

⎠

⎞

⎜⎜⎜

⎝

⎛•

⎟⎟⎟

⎠

⎞

⎜⎜⎜

⎝

⎛

•⎟⎟⎟

⎠

⎞

⎜⎜⎜

⎝

⎛

=⎟⎟⎟

⎠

⎞

⎜⎜⎜

⎝

⎛=

+ βα

α

δ

δ

τττ

µµµ

θθθθ

θθ

θθθθθθ

i/2i-

i-

i-

i-

ee

e

e

CP

CP

0000001

00

001

0010

0

10000

2/

2323

2323

1313

1313

1212

1212

321

321

e3e2e1

cossin-sincos

cossin-

sincoscossin-sincos

UUUUUUUUU

U

Solar νKamLAND

Atmospheric νK2K

Neutrinolessdouble beta

decay

Chooz/Palo Verde

information onCP is here

A possible representation of thePontecorvo-Maki-Nakagawa-Sakata matrix

θ12~32° θ13<7° @ 90%CL θ23~45°

Off axisFuture reactorsFuture solar

ν exp.Minos et al

Neutrinofactory ?


Sign of ∆m213 (Future accelerator experiments)

2.8 eV

From tritium

endpoint(M

aintzand Troitsk)

0.3 eV

From 0νββ

if νis M

ajorana

?

Oscillations give the proof that neutrino massesare non-zero, but we still do not know the absolute

mass scale and the hierarchy

~1 eV

From W

MA

P

Time of flight from

SN1987A

(PDG 2002)

~20 eV

~8.3·10-5 eV2

~8.3·10-5 eV2

solar~2.7·10-3 eV2

solar~2.7·10-3 eV2


MeVeHpp e 42.02 +++→+ + ν

ννee are abundant byare abundant by--products of products of nuclear fusion in the sunnuclear fusion in the sun

MeVHpep e 44.12 ++→++ − ν

MeVHepH 49.532 ++→+ γ

MeVpHeHe 86.12233 ++→+ α MeVBeHe 59.173 ++→+ γα eepHe να ++→+ +3

MeVLieBe e 8617.077 +++→+ − νγ MeVBpBe 14.087 ++→+ γ

MeVpLi 35.177 ++→+ αα MeVeBeB e 6.1488 +++→ + ν

MeVBe 38 ++→ αα

““pp” 99.75%pp” 99.75%

86%86% ““hephep” 2.4*10” 2.4*10--55

““77BeBe”” 99.89%99.89%

““pep” 0.25%pep” 0.25%

0.11%0.11%

14%14%

““88BB”” 0.11%0.11%


L=10L=108 8 kmkm

But neutrinos are producedBut neutrinos are produceddeep inside the Sun, wheredeep inside the Sun, wheremost the fusion reactionsmost the fusion reactionstake placetake place

Matter effectsMatter effectsplayplay an essential rolean essential role

The detectors are located far away from the Sun


Several experiments detecting solar neutrinosSeveral experiments detecting solar neutrinos

Chlorine: Chlorine: 3737Cl+Cl+ννee3737Ar+eAr+e--

HomestakeHomestake mine (US) Taking data from 1967mine (US) Taking data from 1967--2002 (!) 2002 (!) The “father” of all solar neutrino experimentsThe “father” of all solar neutrino experiments

Gallium: Gallium: 7171Ga+Ga+ννee7171Ge+eGe+e--

SAGE (SAGE (BaksanBaksan, Russia), , Russia), GallexGallex and GNO (and GNO (GranGran SassoSasso, Italy) , Italy) Lowest thresholdLowest thresholdCalibrated with a neutrino sourceCalibrated with a neutrino source

CerenkovCerenkov: : ee--++ννee ee--++ννee KamiokandeKamiokande and and SuperKamiokandeSuperKamiokande (Japan), SNO (Sudbury, Canada)(Japan), SNO (Sudbury, Canada) Largest statistics Largest statistics See See D.Casper’sD.Casper’s talktalk

CerenkovCerenkov: D: Dνν scatteringscattering SNO (Sudbury, Canada)SNO (Sudbury, Canada) For the first time measure For the first time measure ννee and and ννXX separatelyseparately See See D.WallerD.Waller’’ss talktalk

Radioc

hemical,

no r

eal-

time

info

rmat

ion


Neutrino energy spectrum includes lines and continuaNeutrino energy spectrum includes lines and continua


HomestakeHomestake Mine, Lead SDMine, Lead SD1400 m underground1400 m underground

615 tons of 615 tons of perchloroethileneperchloroethilene(C(C22ClCl44))

2.2*102.2*103030 atoms of atoms of 3737ClCl3636Ar or Ar or 3838Ar added to the Ar added to the

fluid as carrier gasfluid as carrier gas


30 years of solar neutrinos with the Chlorine detector30 years of solar neutrinos with the Chlorine detectorExpectedExpectedfrom

SSMfrom

SSM


1 SN

U =

1

1 SN

U =

1 νν

inte

ract

ion/

sec

per

10inte

ract

ion/

sec

per

103636

targ

et a

toms

targ

et a

toms


7171 Ga ha

s lowe

r thre

shold:

Ga has

lower

thresh

old:

to dat

e, onl

y tech

nique

to dat

e, onl

y tech

nique

sensiti

ve to

pp neu

trinos

!

sensiti

ve to

pp neu

trinos

!

SAGE, Baksan

In In GallexGallex/GNO 30.3 ton of/GNO 30.3 ton ofGaGa in aqueous solution of in aqueous solution of GaClGaCl44. . 7171GeClGeCl44 is volatileis volatileand is purged/countedand is purged/counted

28 28 -- 50 ton of metallic50 ton of metallicGaGa kept liquid (>29.8 C)kept liquid (>29.8 C)

Extraction by Extraction by HClHCl etch andetch andGeCl4 and GeCl4 and ArAr purgepurge


Both Both GaGa experiments haveexperiments havebeen calibrated with a been calibrated with a 5151CrCr

source of about 1 source of about 1 MCiMCi

51Cr source measurements

SAGE dataSAGE data

SNU

SNU

ExpectedExpectedfrom SSMfrom SSM


In order to better understand the situation it would be In order to better understand the situation it would be nice to also measure thenice to also measure thetotaltotal number of neutrinosnumber of neutrinosfrom the Sun, from the Sun, all flavors togetherall flavors together

The SNO detector:The SNO detector:1 1 ktonkton of heavy waterof heavy water


Charged Current (CC): Charged Current (CC): ννee+d+d⇒⇒p+p+ep+p+e--

Electron neutrinos onlyElectron neutrinos only

νxνx

e-e-

e-

dp

p

νe

d p

n

νxνx

Neutrino interactions in DNeutrino interactions in D22OO

Elastic Scattering (ES): Elastic Scattering (ES): ννxx+ e+ e-- ⇒⇒ ννxx +e+e--

0.1540.154••σσ((ννee)=)=σσ((ννµµ)=)=σσ((ννττ))this is all this is all SuperKSuperK seessees

Neutral Current (NC): Neutral Current (NC): ννxx+d+d⇒⇒p+n+p+n+ννxx

Same for all neutrino Same for all neutrino flavors !flavors !


Energy Unconstrained

Remarkably the SNO measurement gives Remarkably the SNO measurement gives ΦΦNCNC>>ΦΦCCCC

So νe are missing, but the totalnumber of neutrinos is right !

Phys. Rev.Lett. 89 (2002) 011301

For upFor up--toto--date results date results see Waller’s talksee Waller’s talk


5.53.69 ±

1 SN

U =

1

1 SN

U =

1 νν

inte

ract

ion/

sec

per

10inte

ract

ion/

sec

per

103636

targ

et a

toms

targ

et a

toms

3.59.66 ±


Global fit to all solar neutrino Global fit to all solar neutrino expsexpseliminates most of the solutionseliminates most of the solutions

except for the MSWexcept for the MSW--LMA solutionLMA solution(The solar neutrino anomaly is(The solar neutrino anomaly is

a sort of neutrinoa sort of neutrino--birefringencebirefringenceof dense matter occurring because of dense matter occurring because

neutrinos have finite massesneutrinos have finite masses---- see Boris see Boris KayserKayser’’ talk)talk)

Clearly all this smells of flavor mixing…Clearly all this smells of flavor mixing…


All of this is very interesting…All of this is very interesting…

…but wouldn’t it be great if we could …but wouldn’t it be great if we could reproduce it with artificial means ?reproduce it with artificial means ?


ννee

ννee

ννee

ννee

ννee

ννee

ννee

ννeeννee

ννe e detectordetector

nucle

ar

nucle

ar

reac

tor

reac

tor

ννxx ??

LL

Look for a deficit of Look for a deficit of ννee and spectraland spectraldistortions at a distance Ldistortions at a distance L

Nuclear reactors are very intense sources of Nuclear reactors are very intense sources of ννee derivingderivingfrom betafrom beta--decay of the neutrondecay of the neutron--rich fission fragmentsrich fission fragments

NN

nn

nnnn

nnNN22

NN11

e-

eν

N’N’22

N’N’11


Example: 235U fission

nXXnU 22123592 ++→+

94 140

Zr9440 Ce140

58

stable nuclei with Amost likely from fission

together these have98 protons and136 neutrons

so, on average 6 n have to decay to 6 p to reach stable matter


fissionfissionMeV

e /6/200

ν

A typical large powerA typical large powerreactor producesreactor produces3 3 GWGWthermalthermal and and

66••10102020 antineutrinos/santineutrinos/s

Power/commercial reactors are generally usedsince only requirement is to have large power

the Chooz plant in France


>99.9% of >99.9% of νν areareproduced by fissions inproduced by fissions in235235U, U, 238238U, U, 239239Pu, Pu, 241241PuPu

-

{contribution <10-3

not taken into account for neutrino

flux calculations


nepe +→+ +ν)2.2( MeVdnp γ+→+

sµτ 200≈

10-40 keV

Eνmeasurement

Event tagging by coincidence in time, space and energy of the neutron capture

++ +−++≅epnne

mMMTTE )(ν

A specific signature is provided by the inverseA specific signature is provided by the inverse--ββ reactionreaction

1.8 MeV

{{

→→ only ~1.5 antineutrinos/fission can be detectedonly ~1.5 antineutrinos/fission can be detected

Threshold: Threshold: EEνν>1.8MeV>1.8MeV


The The ννe e energy spectrumenergy spectrum

ν e+p→

n+e+

cros

sse

ction

(10-

43cm

2 )νν ee

+p→

n+e

+p→

n+e++

cros

scr

oss

sect

ion

(10

sect

ion

(10--

4343cmcm

22 ))

Eν (MeV)

Reactor Reactor ννee spectrum (spectrum (a.ua.u.).)Observed spectrum (Observed spectrum (a.ua.u.).)


Statist

ical e

rrors

only

An experimentrelevant for

solar ν will have~100 km baselineand hence willneed a huge

detector and a “huge source”


~1 km high Mt Ikenoyama


Many reactors contribute to the antineutrino flux at Many reactors contribute to the antineutrino flux at KamLANDKamLAND**EEνν>3.4MeV >3.4MeV ((EEpromptprompt>2.6MeV)>2.6MeV)

4.84.87.87.8··10103317.417.466986986YonggwangYonggwang6.16.19.99.9··10103311.511.544712712UlchinUlchinSouth Korea

South Korea

4.64.67.57.5··1010339.29.244735735KoriKori4.34.37.17.1··1010338.28.244709709WolsongWolsong

5.15.18.38.3··1010336.06.033561561IkataIkata6.36.31.01.0··1010443.83.822401401SimaneSimane9.39.31.51.5··1010446.56.533431431OnagawaOnagawa

2.12.13.43.4··1010335.35.322830830SendaiSendai4.84.87.87.8··10103310.110.144755755GenkaiGenkai

1.41.42.32.3··1010333.33.322783783TomariTomari

31.131.15.15.1··10104414.214.266349349Fukushima1Fukushima155.255.29.09.0··1010441.61.6118888SikaSika

29.529.54.84.8··10104413.213.244345345Fukushima2Fukushima2

62.562.51.01.0··1010554.54.522138138TsurugaTsuruga

Total NominalTotal Nominal

JapanJapan

74.374.31.21.2··10105510.210.244191191TakahamaTakahama114.3114.31.91.9··10105513.713.744179179OhiOhi

62.062.01.01.0··1010554.94.933146146MihamaMihama62.062.01.01.0··10105510.610.644214214HamaokaHamaoka

181.7181.7

3.33.3

24.324.3

PPthermtherm

(GW)(GW)

1.31.3··101066

1.61.6··101044

4.14.1··101055

FluxFlux(cm(cm--2 2 ss--11))

803.8803.87070--

10.110.111295295Tokai2Tokai2

254.0254.077160160KashiwazakiKashiwazaki

Rate Rate nooscnoosc**

(yr(yr--11 ktkt--11))Cores Cores (#)(#)

Dist Dist (km)(km)SiteSite

Deta

iled

powe

r an

d fu

elDe

taile

d po

wer

and

fuel

Compo

sition

calcu

lation

use

dCo

mpo

sition

calcu

lation

use

d

From electrical From electrical powerpower

Japanese averageJapanese averagefuel usedfuel used


The total electric power produced “as a The total electric power produced “as a byby--product” of the product” of the ννs is:s is:

••~60 GW or...~60 GW or...••~4% of the world’s manmade power or…~4% of the world’s manmade power or…••~20% of the world’s nuclear power~20% of the world’s nuclear power


A limited range of baselines contribute to the fluxA limited range of baselines contribute to the fluxof reactor antineutrinos at of reactor antineutrinos at KamiokaKamioka

Over the data periodOver the data periodReported hereReported here

Korean reactorsKorean reactors3.43.4±±0.3%0.3%

Rest of the worldRest of the world+JP research reactors+JP research reactors

1.11.1±±0.5%0.5%

Japanese spent fuelJapanese spent fuel0.040.04±±0.02%0.02%


KamLANDKamLAND: : KamKamiokaioka LLiquid scintillatoriquid scintillatorAAntintiNNeutrinoeutrino DDetectoretector

••1 1 ktonkton liqliq. . ScintScint. Detector. Detector

in the in the KamiokandeKamiokande caverncavern

••1325 17” fast PMTs1325 17” fast PMTs

••554 20” large area PMTs554 20” large area PMTs

••34% photocathode coverage34% photocathode coverage

••HH22O O CerenkovCerenkov veto counterveto counter


The completed detector, looking upThe completed detector, looking up


Scintillator is a blend ofScintillator is a blend of20% pseudocumene and 20% pseudocumene and 80% 80% dodecanedodecane

Different density Different density paraffinesparaffines are usedare usedto tune the density of to tune the density of buffer to 4buffer to 4··1010--44 ofofthat of the scintillatorthat of the scintillator

PPO concentration is PPO concentration is 1.52 1.52 g/lg/l in scintillatorin scintillator


Autoradiography of KamLANDAutoradiography of KamLAND

Top flange and Top flange and chimney regionchimney region

Central thermometerCentral thermometer

BalloonBalloon

Bottom flangeBottom flangeand plumbingand plumbing

In this region measure

238U = (3.5±0.5)x10 -18g/g


A brief history of A brief history of KamLANDKamLAND

369.7369.7Oct Oct -- Jan 11Jan 1120042004Run BRun B

515.1515.1Mar 9, 2002 Mar 9, 2002 ––Jan 11, 2004Jan 11, 2004DataData--set presented hereset presented here††

Jan/Feb 2003Jan/Feb 2003

Mar 9 Mar 9 –– Oct 6Oct 620022002

Jan 2002Jan 2002

DatesDates Live timeLive time(days)(days)

--Electronics upgrade & 20” Electronics upgrade & 20” PMT commissioningPMT commissioning

145.4145.4**Run ARun A(data(data--set of 1set of 1stst paper)paper)

--Start data takingStart data taking

* Was

145

.1 w

ith

old

analys

is

†† T.ArakiT.Araki et al,et al, arXiv:heparXiv:hep--ex/0406035 Jun 13, 04ex/0406035 Jun 13, 04submitted to Phys Rev submitted to Phys Rev LettLett


z

VertexingVertexing is performed using timing from the 17” PMTsis performed using timing from the 17” PMTs

-65 (1.1MeV)-68 (1.0MeV)

-60 (2.6MeV)Am/Be(~8MeV)


Tagged Tagged cosmogenicscosmogenics can be used for calibrationcan be used for calibration

1212BB

1212NN

Fit to data shows that12B:12N ~ 100:1

τ=29.1msQ=13.4MeV

τ=15.9msQ=17.3MeV

µ


Energy calibration uses discrete Energy calibration uses discrete γγ and and 1212B/B/1212NN

68Ge

65Zn

60Co

n-p

Carefully include Carefully include BirksBirks law, law, CherenkovCherenkov and light absorption/opticsand light absorption/opticsto obtain constants for to obtain constants for γγ and and ee––type depositionstype depositions

n-12C

σσ/E ~ 6.2% at 1MeV/E ~ 6.2% at 1MeV


Estimate of total volume and Estimate of total volume and fiducialfiducial fractionfraction


neutronsneutrons

Fraction of volume Fraction of volume insideinside the the fiducialfiducial radius verifiedradius verifiedusing using µµ--producedproduced 1212B/B/1212N and n (assumed uniform)N and n (assumed uniform)

1212B/B/1212NN


-- RRpromptprompt, delayed, delayed < 5.5 m< 5.5 m-- ∆∆RRee--nn < 2 m< 2 m-- 0.5 0.5 µµs < s < ∆∆TTee--nn < 1 ms< 1 ms-- 1.8 MeV < 1.8 MeV < EEdelayeddelayed < 2.6 MeV< 2.6 MeV-- 2.6 MeV < 2.6 MeV < EEpromptprompt < 8.5 MeV< 8.5 MeV

Tagging efficiency 89.8%Tagging efficiency 89.8%

…In addition:…In addition:-- 2s veto for showering/bad 2s veto for showering/bad µµ-- 2s veto in a R = 3m tube along 2s veto in a R = 3m tube along tracktrack

DeadDead--time 9.7%time 9.7%

Selecting antineutrinos, Selecting antineutrinos, EEpromptprompt>2.6MeV>2.6MeV

543.7

ton

543.7

ton5.5 m5.5 m

fiducialfiducial cutcut

Balloon edgeBalloon edge


2.52.5Antineutrino spectrumAntineutrino spectrum0.20.2Antineutrino xAntineutrino x--sectionsection

1.01.0Fuel compositionFuel composition0.010.01Time lagTime lag

1.61.6Cuts efficiencyCuts efficiency

2.12.1Reactor Reactor PPthermalthermal

0.060.06Live timeLive time

4.24.2FiducialFiducial fractionfraction

%%SystematicSystematic

6.56.5TotalTotal

2.32.3Energy threshold Energy threshold

2.12.1Scintillator volumeScintillator volume


Inconsistent with simple 1/RInconsistent with simple 1/R22 propagation propagation at 99.995% CLat 99.995% CL

Observed events 258No osc. expected 365±24(syst)Background 7.5±1.3

ResultsResults

(Observed(Observed--Background)/Expected = 0.686Background)/Expected = 0.686±±0.044(stat)0.044(stat)±±0.045(syst)0.045(syst)

Caveat: this specific number does not have an absolute meaning iCaveat: this specific number does not have an absolute meaning in n KamLANDKamLAND, , since, with oscillations, it depends on which reactors are on/ofsince, with oscillations, it depends on which reactors are on/offf

766.3 766.3 tonton··yryr


2003 saw a substantial dip in reactor antineutrino flux2003 saw a substantial dip in reactor antineutrino flux


90% CL90% CL

Good correlation with reactor fluxGood correlation with reactor flux

Expected fo

r no o

scilla

tions

Expected fo

r no o

scilla

tions

(But a horizontal line still gives a decent fit with χ2=5.4/4)

Fit constrainedFit constrainedthrough knownthrough knownbackgroundbackgroundχ2=2.1/4

~0.03 for~0.03 for3TW3TW

hypotheticalhypotheticalEarth coreEarth corereactorreactor


Energy spectrum now adds substantial informationEnergy spectrum now adds substantial information

Best fit toBest fit tooscillations:oscillations:

∆∆mm22=8.3=8.3··1010--55 eVeV22

sinsin2222θθ=0.83=0.83

StraightforwardStraightforwardχχ22 on the on the histohisto

is is 19.6/1119.6/11

Using equalUsing equalprobability binsprobability binsχχ22//dofdof=18.3/18=18.3/18

(goodness(goodnessof fit is 42%)of fit is 42%)

A fit to a simple rescaled reactor spectrumA fit to a simple rescaled reactor spectrumis excluded at 99.89% CL (is excluded at 99.89% CL (χχ22=43.4/19)=43.4/19)


∆∆mm22=8.3=8.3··1010--55 eVeV22

sinsin2222θθ=0.83=0.83

LMA2 excludedLMA2 excludedat 99.6% CLat 99.6% CL

UnUn--binned likelihood fit to 2binned likelihood fit to 2--flavor oscillationsflavor oscillations

““LMA0” disfavoredLMA0” disfavoredat 94% CLat 94% CL

All solar All solar ννexperimentsexperiments


A shapeA shape--only fit givesonly fit givessimilar resultssimilar results

∆∆mm22=8.3=8.3··1010--55 eVeV22

sinsin2222θθ=0.98=0.98


KamLANDKamLAND uses a range of L and uses a range of L and it cannot assign a specific L to each eventit cannot assign a specific L to each eventNevertheless the ratio of detected/expectedNevertheless the ratio of detected/expected

for Lfor L00/E (/E (or 1/Eor 1/E) is an interesting quantity, as it decouples) is an interesting quantity, as it decouplesthe the oscillation patternoscillation pattern from the reactor energy spectrumfrom the reactor energy spectrum

no oscillation expectationno oscillation expectation

HypotheticalHypotheticalsingle 180kmsingle 180km

baselinebaselineexperimentexperiment


More exotic, nonMore exotic, non--oscillations models for the antineutrinooscillations models for the antineutrinochannel start being less favored by datachannel start being less favored by data

DecayDecay**

excluded atexcluded at95% CL95% CL

DecoherenceDecoherence††

excluded atexcluded at94% CL94% CL

*V.Barger et al. Phys. Rev. Lett. 82 (1999) 2640†E.Lisi et al., Phys. Rev. Lett. 85 (2000) 1166


Combined solar Combined solar νν –– KamLANDKamLAND 22--flavor analysisflavor analysis

Includes (small) matter effectsIncludes (small) matter effects

07.009.040.0tan

105.06.02.8

122

25212

−+=

×−+=∆ −

θ

eVm


…it took 35 years… but we have:…it took 35 years… but we have:1)1) detected neutrinos from the sundetected neutrinos from the sun2)2) found that part of the neutrino flux is missingfound that part of the neutrino flux is missing3)3) found that only found that only ννee are missingare missing4)4) found that matter effects in the sun (MSW effect)found that matter effects in the sun (MSW effect)

are responsible for the deficitare responsible for the deficit5) found that neutrinos have finite masses (required5) found that neutrinos have finite masses (required

for MSW)for MSW)6) identified mixing parameters 6) identified mixing parameters ∆∆mm1212

22, , θθ12127) found that we can reproduce this effect artificially7) found that we can reproduce this effect artificially

with vacuum oscillations with the same with vacuum oscillations with the same ∆∆mm121222, , θθ1212

8) found that 8) found that νν and antiand anti--νν behave the same waybehave the same way9) found that flavor mixing works better than other9) found that flavor mixing works better than other

scenarios (e.g. decay)scenarios (e.g. decay)10) found that our model for the sun (SSM) works10) found that our model for the sun (SSM) works

very wellvery well


The otheroscillations:Atmosphericneutrinos

Higher energyphenomenon

Measurementsdominated by

SuperK


SuperKamiokande:the largest “artificial”

water Cerenkov detectorever built (50 kton)

SK1 1996-2001>11146 50cm PMTs40% photocathode

22.5kton fiducial mass

2003-20055182 PMTs recovered

19% photocathodeK2K beam

2006-…Original PMT coverage

T2K beam

SSI 2004 Experimental Neutrino Oscillations - Gratta 56E.Kearns, Nu2004

A composite data-set


SSI 2004 Experimental Neutrino Oscillations - Gratta 58E.Kearns, Nu2004e µ


The oscillatory pattern is now also visible with atmospheric neutrinos

And flavor oscillationis favored over other

models fordisappearance


Parameter regions fit by different channels nicely overlap

A 3 flavor analysisfavors νµ-ντoscillation as

responsible forthe atmosphericneutrino anomaly(more on this

later…)


Again, the quest is open to observe the oscillationphenomenon with artificial neutrinos

• 12 GeV KEK protons• Mini-K (1kton water + other detectors)

near detector (100m) 1011 νµ every 2.2s• Super-K at 250km 106 νµ every 2.2s (detect ~1event/2days)• 8.9·1019 p.o.t. collected in ~3.5 yrs

SSI 2004 Experimental Neutrino Oscillations - Gratta 62T.Nakaya, Nu2004

In the 3.5 yrs of datathe atm nu backgroundin the KEK beam spillwindow is 10-2 events

Although rate is lowbackground greatly

reduced by beam spilltiming (0.83 ms delay,synchronized offline

using GPS)

-4 -2 0 2 4Tdiff(µs)

104

103

102

10

1

15

10

5

0


Expected no oscillation rate: 6.110.109.150 +

−

no oscill,floating

normalization

K2K establishes:

• νµ disappearance at 2.9σ(standard physics

has 0.33% CL)• Eν spectral distortion at 2.5σ

(standard physicshas 1.1% CL)

Combined we have a 3.9σ effect(standard physics has 0.011% CL)


approximate90% CL

from globalSK fit to

atmosphericneutrinos


What we have discovered:What we have discovered:

There is mixing involving νe with best fit at ∆m2=8.3·10-5 eV2 and θ=32° (solar/KamLAND)

There is also mixing involving νµ with best fit at∆m2=2.7·10-3 eV2 and θ=45° (atmospheric/K2K)

If there are only 3 neutrino families, since the twomass differences are of different order of magnitude, we expect to find a third ∆m2 similarto the larger of the two above

Documents

Neutrino Oscillations: experimental triumphs, remaining ... · Neutrino Oscillations: experimental triumphs, remaining puzzles ... SAGE (Baksan, Russia), Gallex and GNO (Gran Sasso,