Solar Neutrino Problem

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Solar Neutrino Problem
Rosa María Durán Delgado
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Contents

• Origin of solar neutrinos
• Experiments
• The Problem
• Possible Explanations
• The Solution
• Outlook

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Origin of solar neutrinos

• Nuclear reactions

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Origin of solar neutrinos

• p-p chain

(p-p I chain)
(p-p II chain)
(p-p III chain)
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Origin of solar neutrinos

• Expected fluxes at Earth
• Qp-p 26.73 MeV
• Q Qp-p - Q? ? 25 MeV ? ?

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Experiments

• Chlorine experiment
• Reaction
• E gt 0.8 MeV ? mostly
  8B neutrinos
• Experiment
• Results

Inferred flux ? 2 or 3 lower than the prediction
? Solar neutrino problem
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Experiments

• Kamiokande ? SuperKamiokande
• Reaction ?
  Cherenkov radiation
• E gt 7 MeV ? only
  8B neutrinos
• Experiment
• Results

Inferred flux ? 2 lower than the
prediction Neutrinos come from the sun!
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Experiments

• SAGE GALLEX
• Reaction
• E gt 0.23 MeV ? mostly pp
  neutrinos
• Results

Inferred flux ? 65 prediction
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Possible Explanations

• Standard solar model is not right
• Other chains more efficient
• Lower Tc
• Solar luminosity ? Interior mixing
• ?T lower ? decrease ? ? Radiative diffusion

• Experiments are wrong

• Something happens to the ?

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But

• Precise agreement (prediction-measurement) for
  sound speeds

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The Solution

• SNO

• Reaction
• Neutral-current reaction ? 2H ? ? p n
• Charge-current reaction ? 2H ? ? 2p e-
  ? Cherenkov radiation
• Results
• Flux of ?e 1.75 106 cm-2s-1 ??
  1/3 Predicted flux
• Flux of ?e, ??, ?? 2.32 106 cm-2s-1 ,, ?
  (?? (?) e-) ? 0.15? (?e e-)
• Deduced total flux 5.44 106 cm-2s-1

Yes!
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The Solution

• Electron neutrinos produced by nuclear reactions
  inside the Sun oscillate (change flavour) on
  their journey to Earth.

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Outlook

• Particle physics and Cosmology
• Detectors for low-energy neutrinos

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