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A Primer on Solar Neutrinos

A Primer on Solar Neutrinos. Astrophysics Journal Club January 29, 2002. Randy Johnson. Outline. Solar Nuclear Reactions Standard Solar Model Experimental Results Chlorine Experiment Gallium Experiment Water Č erenkov Counters Explanation???. References. Standard Solar Model:

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A Primer on Solar Neutrinos

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  1. A Primer on Solar Neutrinos Astrophysics Journal Club January 29, 2002 Randy Johnson Outline • Solar Nuclear Reactions • Standard Solar Model • Experimental Results • Chlorine Experiment • Gallium Experiment • Water Čerenkov Counters • Explanation???

  2. References Standard Solar Model: Bahcall, Pinsonneault, and Basu, Astrophy. J. 555, 990(2001) Clayton, Principles of Stellar Evolution and Nucleosynthesis Bahcall, Neutrino Astrophysics Chlorine Experiments: Cleveland, et al., Astrophy. J. 496, 505(1998). Gallium Experiment: SAGE: PRL 83, 4686 (1999). Gallex, GNO: Phys. Lett. B490, 16(2000). Water Detectors: Super-K: PRL 86, 5656(2001). SNO: Ahmad, et al., PRL 87, 071301 (2001).

  3. Solar Nuclear Reactions But what are the neutrino energies? Actual nuclear reactions

  4. Energy Scales Temperature at center of sun: T=15.6x106oK E=kT=1.4 keV Energy to get 2 proton to within 1 Fermi: E=1.4 MeV Essentially no two protons get close enough to react. Must tunnel through repulsive barrier. 1.4 keV would keep most particles about 1 Angstrom away! Density at center of sun: r = 158 g/cc = 100 nucleons/Angstrom3

  5. Production of Deuterium -Rate Limiting Reaction • = 1010 years Bahcall Calculation <qn > = 0.265 MeV qn = 1.442 MeV 1% of primary rate

  6. Helium-3 • = .3 sec • = 105 years 10% rate 10-7 rate <qn > = 9.625 MeV

  7. Beryllium-7 • = 1 month • = 5 min .1% rate <qn > = 6.7 MeV

  8. CNO Cycle Secondary chain for sun More important for bigger stars

  9. Hydrostatic Equilibrium Energy Transport: Equation of State: Energy Production: Boundary Condition: Solar Model

  10. Neutrino Reaction Summary Reaction n Energy Flux at earth 0.265 MeV 6 1.442 MeV .014 9.625 MeV .0000008 .4, .8 MeV .47 .00058 6.7 MeV .1 CNO cycle .8 MeV

  11. Ga experiment Cl experiment Neutrino Flux Water experiment From Bahcall, Neutrino Astrophyiscs, 1989

  12. Where Are the Neutrinos Coming From? Temperature

  13. Chlorine Experiment 615 tons C2Cl4 Ethresh = .814 MeV Detection: + Auger electron Production Rate: 1.5 atoms/day (SSM)

  14. Homestake Results 8+/-1 2.56+/-.16+/-.16 SNU Cleveland, et al., Astrophys. J. 496, 505(1998)

  15. Predicted Rate (BP2000)

  16. Gallium Experiment Ethresh = .2332 MeV 55 Tons Gallium SAGE Production Rate: 2.1 atoms/day (SSM) Gallex - GNO Production Rate: 1.2 atoms/day (SSM)

  17. SAGE Results 128+9-7 SNU 77+/-6+/-3 SNU

  18. Gallex Results Gallex+GNO 74+/-8 SNU SSM =128+9-7 SNU

  19. Predicted Rate (BP2000)

  20. Water Čerenkov Counters Super-K: 50,000 metric tons of water Super-K Threshold 5 MeV Only B8 and hep neutrinos observed Reaction does not distinguish neutrino flavor

  21. Super-K Neutrino Čerenkov ring gives direction Amount of light gives energy Electron Čerenkov Light

  22. Super-K Events Muon with Michelle Electron Solar Neutrino

  23. Super-K Results Angle from Solar Direction Expected Annual Variation Expected Rate = 5.1 SNU Observed = 2.4+/-.1 SNU

  24. Summary of Results

  25. Possible Explanations • Standard Solar Model is wrong • Neutrino Physics is wrong Neutrino Oscillations If neutrinos have mass and if there is an interaction that couples them, then:

  26. SNO Experiment Sudbury Mine Canada Deuterium Central Ball surrounded by PMTs and water shield

  27. SNO vs. Super-K Experiments SNO’s or Super-K’s Elastic Scattering Elastic scattering sensitive to all neutrinos ne more efficient than others SNO’s Charged Current Reaction Only sensitive to ne

  28. SNO Results

  29. SNO vs. Super-K Comparison

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