The solution to the solar n problem
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The Solution to the Solar n Problem. Jordan A. Goodman University of Maryland January 2003 Solar Neutrinos MSW Oscillations Super-K Results SNO Results Kamland Results Overall Results. Our current view of underlying structure of matter. P is uud N is udd p + is ud k + is us

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The Solution to the Solar n Problem

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The Solution to the Solar n Problem

Jordan A. Goodman

University of Maryland

January 2003

  • Solar Neutrinos

  • MSW Oscillations

  • Super-K Results

  • SNO Results

  • Kamland Results

  • Overall Results


Our current view of underlying structure of matter

  • P is uud

  • N is udd

  • p+ is ud

  • k+ is us

  • and so on…

}Baryons

(nucleons)

}Mesons

The Standard Model


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

Facts about Neutrinos


Neutrinos

They only interact weakly

If they have mass at all – it is very small

Why do we care about neutrinos?

  • 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!


Solar Neutrinos


Solar Neutrino Spectrum


Solar Neutrino Experiment History

  • Homestake - Radiochemical

    • Huge tank of Cleaning Fluid

    • ne + 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

    • ne + 71Ga e- + 71Ge

    • 4 years at ~0.75 ev /day

    • ~2/3 SSM

  • Kamiokande-II and -III

    • 8B neutrinos only

    • ne Elastic Scattering

    • 10 years at 0.44 ev /day

    • ~1/2 SSM

    • (Koshiba 2002 Nobel Prize)


The Solar Neutrino Problem


Disappearing Neutrinos?

  • All of these experiments (except SNO) are sensitive mostly to ne

    • The energies are too low to produce m or t so 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


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


=Electron n

=Muon n

n1n2

n1n2

Muonn

Electronn

Neutrino Oscillations


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


MSW Oscillations

(Mikheev, Smirnov, Wolfenstein)


Oscillation Parameter Space

LMA

SMA

LOW

VAC


Solar Neutrinos in Super-K

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


Cherenkov Radiation

Aircraft moves through

air faster than speed of

sound.

Sonic Boom

Sonic boom


Cherenkov Radiation

When a charged particle moves through

transparent media faster

than speed of light in that

media.

Cone of

light

Cherenkov radiation


Super-K


Super-Kamiokande


Detecting neutrinos

Cherenkov ring on the wall

Electron or muon track

The pattern tells us the energy and type of particle

We can easily tell muons from electrons


A muon going through the detector


A muon going through the detector


A muon going through the detector


A muon going through the detector


A muon going through the detector


A muon going through the detector


Stopping Muon


Stopping Muon – Decay Electron


Low Energy Electron in SK


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


Solar Neutrinos


Energy Spectrum


Seasonal/Sunspot Variation


Day / Night - BP2000+New 8B SpectrumPreliminary


Combined Results netonm,t

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


Combined Results netonsterile

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)


SNO CC Results

Fne= (35 ± 3 )% Fssm


Combining SK and SNO

  • SNO measures Fne= (35 ± 3 )% Fssm

  • SK Measures Fes= (47 ± .5 ± 1.6)% Fssm

  • No Oscillation to active neutrinos:

    • ~3s difference

  • If Oscillation to active neutrinos:

    • SNO Measures just Fne

      • This implies that Fnm,t= ~65% Fssm (~2/3 have oscillated)

    • SK measures Fes =(Fne + (Fnm,t)/6.5)

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


SNO Results (NC)


SNO Results (NC/CC)

  • SNO Results


SNO Results


Combined Results


Kamland – Terrestrial Neutrinos


Reactors Contributing to Kamland


Kamland Results (Dec. 2002)


Kamland


Kamland


All Experiments Combined with Kamland


The Winner

Solar Neutrino Conclusions

  • 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


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