Solar & Atmospheric Oscillation Experiments

Greg Sullivan University of Maryland

Aspen Winter ConferenceJanuary 21, 1999

PastNeutrino Mass & Oscillations

PresentAtmospheric neutrinosSolar neutrinos

Future

PastNeutrino Mass & Oscillations

PresentAtmospheric neutrinosSolar neutrinos

Future

??

e

Can we detect them?In 1934 Bethe & Peierls calculated the

cross section for neutrino interaction of 10-44 cm2.

Nature (London) 133, 532(1934)

“It is therefore absolutely impossible to observe processes of this kind with neutrinos created in nuclear transformations”

“… one can conclude that there is no practically possible way of observing the neutrino.”

“… and it is not necessary to assume interaction in order to explain the function of the neutrino nuclear transformations ...”

In fact, it was some 20 years before they were detected using a nuclear reactor as a source.

Solar Neutrino Spectrum

Solar Neutrinos detected R. Davis and his 37Cl detector

same principle used to try and detect antineutrinos from a nuclear reactor in 1955.

measured the flux of neutrinos from the sun almost continuously since about 1970!

Solar Neutrino Rate in Cl Detector is 1/3-1/2 expected

Astrophysics - Standard Solar ModelNeutrinos from 7Be and 8BVery sensitive to Sun’s core temperature

Particle Physics Solutions --- Neutrino properties are not what we think!

Electron Neutrinos don’t make it to earthMagnetic properties of e change flavor in transit - Neutrino

Oscillations!Non zero neutrino mass!Lepton flavor mixing!

Explanations?

Neutrino Mass & Neutrino Oscillations? What is the mass of the neutrino?

Is it identically zero?If not, Why is it so small?

see-saw mechanism

T h e m o s t g e n e r a l m a s s L a g r a n g i a n f o r o n e n e u t r i n o f l a v o r i s :

L m m m h cm D L R R L L Lc

L R Rc

R . .

w h e r e m D , m L , m R r e p r e s e n t t h e D i r a c , l e f t - h a n d e d M a j o r a n aa n d r i g h t - h a n d e d M a j o r a n a m a s s e s . T h i s c a n b e w r i t t e n i nm a t r i x f o r m a s :

L S M Sm

w h e r e ,

S

Mm m

m m

L Lc

R Rc

L D

D R

T h e p h y s i c a l m a s s e i g e n s t a t e s a r e f o u n d b y d i a g o n a l i z i n g t h em a s s m a t r i x . I f w e a s s u m e m L = 0 w e g e t :

mm m

mR D

R1 2

2

221 1

4,

F o r a h e a v y r i g h t - h a n d e d s c a l e m R > > m D , w e g e t t w o m a s se i g e n s t a t e s

m m h e a v y M e V m

mm

ml i g h t s e V

H R W

D

R

( )

( ) '

5 0 5 0 0

1 0 1 02

6

Neutrino Oscillations If mass is not 0 and flavor is not absolutely

conserved then “mixing” may occur between different type of neutrinos. Weak eigenstates of the neutrino are mixtures of the neutrinos with definite mass.

F o r t w o n e u t r i n o s p e c i e s e a n d w e h a v e :

cossin

sincos

21

21

e

w h e r e a n d 2 a r e t h e m a s s e i g e n s t a t e s .

I n a w e a k d e c a y o n e p r o d u c e s a d e f i n i t e w e a k e i g e n s t a t e

t e 0 .

.A t a l a t e r t i m e t h e p r o b a b i l i t y o f t h e f i n a l s t a t e w i l l b e :

sincos 2121

tiEtiE eet

T h e s u r v i v a l p r o b a b i l i t y i s :

GeV

kmeVee E

LmLP

222 27.1

ins2sin1; .

Solar Neutrino Experiments

Homestake - RadiochemicalHuge tank of Cleaning Fluid

e + 37Cl e- + 37Ar

Mostly 8B neutrinos + some 7Be30 years at <0.5 ev/day1/3 SSM

Sage/Gallex - Radiochemical“All” neutrinos

e + 71Ga e- + 71Ge

4 years at ~0.75 ev /day~2/3 SSM

Kamiokande-II and -III 8B neutrinos only

e Elastic Scattering

10 years at 0.44 ev /day~1/2 SSM

Homestake - RadiochemicalHuge tank of Cleaning Fluid

e + 37Cl e- + 37Ar

Mostly 8B neutrinos + some 7Be30 years at <0.5 ev/day1/3 SSM

Sage/Gallex - Radiochemical“All” neutrinos

e + 71Ga e- + 71Ge

4 years at ~0.75 ev /day~2/3 SSM

Kamiokande-II and -III 8B neutrinos only

e Elastic Scattering

10 years at 0.44 ev /day~1/2 SSM

Summary of Results Before Super-K

Four experiments measured versus predicted from solar model

Four experiments measured versus predicted from solar model

Experiment SSM(BP92) DATA DATA/SSM

GALLEX (Ga)

132 7 70 8 0.54

SAGE (Ga)

“ 73 11

Homestake (Cl)

8 1.1 2.55 .25 0.32

Kamioka (H2O)

5.7 .8 2.80 .38 0.49

FROM Langacker -Allowed regions at 95% CL from individual experiments and from the global fit. The Earth effect is included for both time-averaged and day/night asymmetry data, full astrophysical and nuclear physics uncertainties and their correlations are accounted for, and a joint statistical analysis is carried out. The region excluded by the Kamiokande absence of the day/night effect is also indicated.

BP95

Atmospheric Neutrinos

Absolute Flux Predicted to ~20% :

• primary CR spectrum

• geomagnetic cutoff

• hadron production modeled from accelerator data

2

ee

Ratio predicted to ~ 5%

Atmospheric Neutrino Anomaly

The Observed Ratio of /e is too lowProduced when pions generated in the upper

atmosphere by cosmic rays decay.

Predicted Ratio of /e ~ 2

Observed Ratio is ~ 1

Particle Physics Solutions --- Neutrino properties are not what we think!

Muon Neutrinos don’t make it to earth

change flavor in transit - Neutrino Oscillations!

Non zero neutrino mass!Lepton flavor mixing!

ee

XNP

Worldwide Results on “R”Before Super-Kamiokande

Two Suggestions of Neutrino Transformation

Solar Neutrinos (~1-15 Mev e)Davis experiment (Cl) saw ~30% of expected

flux of e from 8B & 7Be

Galium experiments showed less than

expected flux of e from all processes

Kamiokande saw ~40% e from 8B

These results can not be reconciled with the standard solar model

Atmospheric Neutrinos (~.1 - 3 GeV) IMB and Kamiokande saw less than

expected ratio of e

One Proposed Explanation was: Neutrino Oscillations

Solar neutrinos might be e

Atmos. neutrinos might be

Super-Kamiokande The Next generation Underground Neutrino Detector.

Detector Characteristics41 m h x 39 m dia.50,000 tonne total/22,000 tonne fiducial11,200 20” PMTs inner detector1,850 8” PMTs anti-detector40% photocathode coverage

Trigger Threshold ~5 MeV Resolution

Energy 16%/(E)1/2 at 10 MeVPosition ~50 cm at 10 MeVAngular ~30 degrees at 10 MeV

Super-Kamiokande is a 50,000 ton water Cerenkov detector at a depth of 1000 meters in the Kamioka Mozumi mine in Japan.

SuperKamiokandeCollaboration

Institute for Cosmic Ray Research, University of Tokyo Gifu University Institute for Nuclear Study, University of Tokyo National Laboratory for High Energy Physics, KEK Kobe University Miyagi Education University Niigata University Osaka University Tokai University Tohoku University Tokyo Institute of Technology Boston University Brookhaven National Laboratory University of California, Irvine California State University, Dominguez Hills Cleveland State University George Mason University University of Hawaii Los Alamos National Laboratory Louisiana State University University of Maryland State University of New York, Stony Brook University of Warsaw University of Washington

Institute for Cosmic Ray Research, University of Tokyo Gifu University Institute for Nuclear Study, University of Tokyo National Laboratory for High Energy Physics, KEK Kobe University Miyagi Education University Niigata University Osaka University Tokai University Tohoku University Tokyo Institute of Technology Boston University Brookhaven National Laboratory University of California, Irvine California State University, Dominguez Hills Cleveland State University George Mason University University of Hawaii Los Alamos National Laboratory Louisiana State University University of Maryland State University of New York, Stony Brook University of Warsaw University of Washington

The Super-K Detector

The Super-Kamiokande Tank During Filling in 1996

Stopping Muon

Electron from decay of stopping muon

Muon - Electron Identification

Sub-Gev (535 days)

Evis < 1.33 GeVPe > 100 MeV/cP> 200 MeV/c

Data MC

1 Ring

e-like 1231 1049

-like 1158 1574

Multi-ring 911 981

)(05.)(026.63.0

/

/syststat

e

e

MC

Data

Multi-Gev (535 days)

Evis > 1.33 GeV

Data MC

1 Ring

e-like 290 236 -like 230 297Multi-ring 533 560

)(08.)(05.65.0

/

/syststat

e

e

MC

Data

Fully Contained

Data MC

Total =-like

301 372

Partially Contained

Worldwide Results on “R”

Detectors continue to runMACRO upward going muonsSoudan IISuper-K muons

If the muon ‘s oscillate, what it look like?

Depletion of relative to e

“double ratio” R

L dependence of flux

Zenith angle dependence

1

/

/

MC

data

e

eR

Zenith Angle Dependence

Survival Probability vs. Distance (1GeV,.003 eV^2)

0

0.25

0.5

0.75

1

10 100 1000 10000

Distance (km)

Pro

ba

bil

ity

GeV

km

E

LmLP

222 27.1

sin2sin1;

Zenith Angle Dependence

Zenith Angle Dependence

L/E Distribution of Atmospheric Neutrinos

The dashed lines show the expected shape for at m2=2.2 x 10-3 eV2 and sin2 2 = 1.

Atmospheric Results

East-West Effect

Zenith Angle Distribution(736 Day Sample)

Zenith Angle Dependence(736 day sample)

MACRO Detector

Data collected ‘89 - Dec ‘97~3 live-years with 6 full SM~480 Upward Going Muon events

R(data/MC)= 0.74 .036sta.046sys.13theo

Probability for no oscillations

P(null) = 14%Best fit mass assuming maximal mixing:

m2 ~ 2 x 10-3 eV2

MACRO upward-going muons

Probabilities Number + ShapeProbability of no oscillations

P(null) 0.1%Best fit oscillation parameters

sin22 = 1.0 , m2 2 x 10-3 eV2

P(best fit) 17%

A Picture of the Sun using Neutrinos in Super-K

10 MeV Electron in Super-K

Super Low Energy (SLE) Data

Solar Neutrino Flux(New 708 Day Sample)

)(013.0)(008.0471.098

syststatSSM

Data

BP

Day-Night Results708 day Sample

)(013.0)(016.0026.0 syststatND

ND

Energy Spectrum708 day + 419 day SLE

Spectrum and Oscillations?

Data favors Vacuum solution (red)small angle MSW (blue) starting to get

squeezed by flatness with SLE data

Hep Neutrinos ? Set limit on hep flux from data

integral of events between Ethres & Eend

Ethres= 17 MeV , Eend= 25MeV

Hep flux < 8 SSM at 90% C.L.Ethres= 19 MeV , Eend= 20 MeV

Hep flux < 20 SSM at 90% C.L.

Seasonal Variation

Energy Dependence of Seasonal Variation for Just-so solution

Seasonal Variation in High Energy Data

Summary of Super-K Results

Atmospheric Neutrinos

Strong Evidence for s) Oscillations

New results consistentHigher statistics may allow separation of

(s)

Solar NeutrinosNo evidence for Day/Night Effect

Squeezes Large Angle SolutionSuper Low E and more statistics

somewhat flattens energy spectrumStarting Squeeze Small Angle

SolutionVacuum (Just-So) solution is still aliveContinue to Run

Postponed the scheduled June ‘99 shutdown

Future ~2000

Atmospheric NeutrinosContinued running of Super-Kamiokande

Neutral Currents ?Distinguish from s

MACRO muons & neutrinosSoudan IIKEK to Super-K (K2K)

Solar NeutrinosSpectral Distortion at High EnergyInstrumental Effect?

Energy Scale & Resolution

LINAC limitationsD-T Generator to make 16N as

calibration source (NSF)Hep Neutrinos?

Need 20 times predicted fluxUse Super-K data >18 MeV to set limit

on hep flux??Statistics?Seasonal Variation needs more data

Atmospheric NeutrinosContinued running of Super-Kamiokande

Neutral Currents ?Distinguish from s

MACRO muons & neutrinosSoudan IIKEK to Super-K (K2K)

Solar NeutrinosSpectral Distortion at High EnergyInstrumental Effect?

Energy Scale & Resolution

LINAC limitationsD-T Generator to make 16N as

calibration source (NSF)Hep Neutrinos?

Need 20 times predicted fluxUse Super-K data >18 MeV to set limit

on hep flux??Statistics?Seasonal Variation needs more data

Future 2000+

Atmospheric NeutrinosAccelerator Experiments (FNAL, CERN,

KEK)Known Neutrino DirectionBetter Neutrino Energy Measurement

Appearance Experiment ??

Solar Neutrinos Continued Super-Kamiokande RunningNew Experiments Soon - should settle the

solar neutrino problemSudbury Neutrino Observatory (SNO)

Canada,US,UK 11 institutions Fill Apr, 98 -- Feb, 99 ?6 mo. Debug & Calibration1 Yr. pure D2O

BorexinoICARUS

Atmospheric NeutrinosAccelerator Experiments (FNAL, CERN,

KEK)Known Neutrino DirectionBetter Neutrino Energy Measurement

Appearance Experiment ??

Solar Neutrinos Continued Super-Kamiokande RunningNew Experiments Soon - should settle the

solar neutrino problemSudbury Neutrino Observatory (SNO)

Canada,US,UK 11 institutions Fill Apr, 98 -- Feb, 99 ?6 mo. Debug & Calibration1 Yr. pure D2O

BorexinoICARUS

SNO Detector

Detector PerformanceThreshold 5MeV - 8B neutrinosEnergy Resolution 14% at 10 MeVCharged Current off D - 26.7 ev/day

measure NEUTRINO energy

- look for spectral distortion with high sensitivity

- seasonal variation over entire spectrumNeutral Current 7.7 ev/day

CC/NC ratio “smoking gun”Electron Scattering 3.0 ev/day

-1000 tonnes of D2O

-6800 feet Underground

-10,000 pmts

SNO Sensitivity

1) CC/NC Ratio

2) Spectrum

Borexino

Detector PerformanceElectron Threshold low enough to

observe 7Be (863 keV) neutrinosReal time measurement of 7Be & 8B46 events/day in 100 ton fiducial volumeFirst Measurement of only the 7Be flux

final ingredient

-300 Tonnes of Scintillator

-2200 Pmt’s

-Gran Sasso

Solar Neutrinos in Near Future

PossibleSolutions

*

Super-K(Boron)

SNO(Boron)

Borexino(Be)*

Boone(Acc)

NoSolarOsc

Flux lowNo specNo D/NNo Seas

Flux low?No SpecCC/NCOK

Meas/exp

1Possible

signal

SmallAngleMSW

SpectralDistortion?

SpectrumCC/NClow

~1/4 NoSignal

LargeAngleMSW

Day/NightDay/NightCC/NClow

~1/2 NoSignal

VacuumOsc Spectrum

Season?

SpectrumSeasonCC/NClow

~1/2 NoSignal

SmallAngleSterile

Spectrum?SpectrumCC/NCOK

~.01 Possiblesignal

*Bahcall Phys Rev D 58

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

Atmospheric NeutrinoOscillations

Need Confirmation of EvidenceFurther Running of Super-k, Soudan,

MACROAccelerator Experiments planned

MINOS at FNALCERN to Gran Sasso

- Disappearance experiments?

Future PossibilitiesMegaton underground Atmospheric

Neutrino detector

Appearance Experiment?5 GeV Neutrinos L/E ~ 1 x 103

L ~ 5000 km