J. Goodman – January 03

The Solution to the Solar Problem

Jordan A. Goodman

University of Maryland

January 2003

• Solar Neutrinos• MSW Oscillations• Super-K Results• SNO Results• Kamland Results• Overall Results

J. Goodman – January 03

Our current view of underlying structure of matter

• P is uud

• N is udd

• is ud

• k is us

• and so on…

• P is uud

• N is udd

• is ud

• k is us

• and so on…

The Standard Model

The Standard Model

}Baryons }Baryons

}Mesons }Mesons

(nucleons)(nucleons)

J. Goodman – January 03

Facts about Neutrinos

• Neutrinos are only weakly interacting

• 40 billion neutrinos continuously hit every cm2 on earth from the Sun (24hrs/day)

• Interaction length is ~1 light-year of steel

• 1 out of 100 billion interact going through the Earth

• 1931 – Pauli predicts a neutral particle to explain energy and momentum non-conservation in Beta decay.

• 1934 - Enrico Fermi develops a comprehensive theory of radioactive decays, including Pauli's particle, Fermi calls it the neutrino (Italian: "little neutral one").

• 1959 - Discovery of the neutrino is announced by Clyde Cowan and Fred Reines

J. Goodman – January 03

Why do we care about neutrinos?

• Neutrinos – They only interact

weakly– If they have mass at all

– it is very small • They may be small, but there sure are a

lot of them!– 300 million per cubic meter left over from the

Big Bang– with even a small mass they could be

most of the mass in the Universe!

J. Goodman – January 03

Solar Neutrinos

J. Goodman – January 03

Solar Neutrino Spectrum

J. Goodman – January 03

Solar Neutrino Experiment History

• Homestake - Radiochemical– Huge tank of Cleaning Fluid

– e + 37Cl e- + 37Ar

– Mostly 8B neutrinos + some 7Be– 35 years at <0.5 ev/day– ~1/3 SSM– (Davis - 2002 Nobel Prize)

• 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– (Koshiba 2002 Nobel Prize)

J. Goodman – January 03

The Solar Neutrino Problem

J. Goodman – January 03

Disappearing Neutrinos?

• All of these experiments (except SNO) are

sensitive mostly to e

– The energies are too low to produce orso they can only see neutral current interactions from other flavors

• If neutrinos could transform from electron type to muon or tau type the data might be understood

• Neutrinos can only “oscillate” if they have different masses– This implies that they have mass!– This would have significant cosmological importance

• A neutrino mass of ~20ev would close the Universe– It would also imply violation of lepton flavor conservation

J. Goodman – January 03

Detecting Neutrino Mass

• If neutrinos of one type transform to another type they must have mass:

• The rate at which they oscillate will tell us the mass difference between the neutrinos and their mixing

GeV

kmeVxe E

LmLP

222 27.1

ins2sin;

J. Goodman – January 03

Neutrino Oscillations

1 21 2

=Electron =Electron

Electron

Electron

1 21 2

=Muon =Muon

Muon Muon

J. Goodman – January 03

Neutrino Oscillations

• Could Neutrino Oscillations solve the solar neutrino problem?– Simple oscillations would require a cosmic conspiracy– The earth/sun distance would have to be just right to

get rid of Be neutrinos

• Another solution was proposed – Resonant Matter Oscillations in the sun

(MSW- Mikheev, Smirnov, Wolfenstein)• Because electron neutrinos “feel” the effect of

electrons in matter they acquire a larger effective mass– This is like an index of refraction

J. Goodman – January 03

MSW Oscillations

Sin 2Spring =

e

Length = Mass

When length (i.e. effective mass) are equal the couplingis enhanced.

Mechanical Analogy for Neutrino Oscillations

In theSun

In theVacuum

Resonance

(Mikheev, Smirnov, Wolfenstein)

J. Goodman – January 03

Oscillation Parameter Space

LMA

LOW

VAC

SMA

J. Goodman – January 03

Solar Neutrinos in Super-K

• The ratio of NC/CC cross section is ~1/6.5

J. Goodman – January 03

Cherenkov Radiation

Aircraft moves throughair faster than speed ofsound.

Sonic boom

J. Goodman – January 03

Cherenkov Radiation

When a charged particle moves throughtransparent media fasterthan speed of light in thatmedia.

Cherenkov radiation

Cone oflight

J. Goodman – January 03

Super-K

J. Goodman – January 03

Super-Kamiokande

J. Goodman – January 03

Detecting neutrinos

Electron or

muon track

Electron or

muon track

Cherenkov ring on the

wall

Cherenkov ring on the

wall

The pattern tells us the energy and type of particle

We can easily tell muons from electrons

The pattern tells us the energy and type of particle

We can easily tell muons from electrons

J. Goodman – January 03

A muon going through the detector

J. Goodman – January 03

A muon going through the detector

J. Goodman – January 03

A muon going through the detector

J. Goodman – January 03

A muon going through the detector

J. Goodman – January 03

A muon going through the detector

J. Goodman – January 03

A muon going through the detector

J. Goodman – January 03

Stopping Muon

J. Goodman – January 03

Stopping Muon – Decay Electron

J. Goodman – January 03

Low Energy Electron in SK

J. Goodman – January 03

Solar Neutrinos in Super-K

• 1496 day sample (22.5 kiloton fiducial volume)• Super-K measures:

– The flux of 8B solar neutrinos– Energy spectrum and direction of recoil electron

• Energy spectrum is flat from 0 to Tmax

– The zenith angle distribution– Day / Night rates– Seasonal variations

J. Goodman – January 03

Solar Neutrinos

)s cm 10 x (syst)0.03(stat) (2.32

ssm) (syst) %0.5%(stat) (45.1%

1-2-608.00.07

1.61.4 -

e

J. Goodman – January 03

Energy Spectrum

J. Goodman – January 03

Seasonal/Sunspot Variation

J. Goodman – January 03

Day / Night - BP2000+New 8B SpectrumPreliminary

(syst)(stat)0.0200.021N)(D

21

DN 0.0130.012-

J. Goodman – January 03

Combined Results e to

SK+Gallium+Cholrine - flux only allowed 95% C.L.

95% excluded by SK flux-independent zenith angle energy spectrum

95% C.L allowed. - SK flux constrained w/ zenith angle energy spectrum

J. Goodman – January 03

Combined Results e to sterile

SK+Gallium+Cholrine - flux only allowed 95% C.L.

95% excluded by SK flux-independent zenith angle energy spectrum

95% C.L allowed. - SK flux constrained w/ zenith angle energy spectrum

(Like SK)

J. Goodman – January 03

SNO CC Results

e= (35 ± 3 )% ssm

J. Goodman – January 03

Combining SK and SNO

• SNO measures e= (35 ± 3 )% ssm

• SK Measures es= (47 ± .5 ± 1.6)% ssm

• No Oscillation to active neutrinos:– ~3 difference

• If Oscillation to active neutrinos:– SNO Measures just e

• This implies that ssm (~2/3 have oscillated)

– SK measures es =(e + ( /6.5)

• Assuming osc. SNO predicts that SK will see es ~ (35%+ 65%/6.5) ssm = 45% ± 3% ssm

J. Goodman – January 03

SNO Results (NC)

J. Goodman – January 03

SNO Results (NC/CC)

• SNO Results

J. Goodman – January 03

SNO Results

J. Goodman – January 03

Combined Results

J. Goodman – January 03

Kamland – Terrestrial Neutrinos

J. Goodman – January 03

Reactors Contributing to Kamland

J. Goodman – January 03

Kamland Results (Dec. 2002)

J. Goodman – January 03

Kamland

J. Goodman – January 03

Kamland

J. Goodman – January 03

All Experiments Combined with Kamland

J. Goodman – January 03

• It looks like the Solar Neutrino problem has been solved!– All Data (except LSND) is now consistent

with the large angle MSW solution– We have ruled out SMA and Low solutions– Disfavor Sterile Neutrino solutions

• Neutrinos have mass!– This confirms the atmospheric neutrino results– Neutrinos contribute approximately as much

mass as all of the visible stars

• Future Experiments – – MiniBoone – LSND effect

Solar Neutrino Conclusions