The Solution to the Solar n Problem

1. 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

2. 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

3. 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

4. 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!

5. Solar Neutrinos

6. Solar Neutrino Spectrum

7. 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)

8. The Solar Neutrino Problem

9. 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

10. 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

11. =Electron n =Muon n n1n2 n1n2 Muonn Electronn Neutrino Oscillations

12. 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

13. MSW Oscillations (Mikheev, Smirnov, Wolfenstein)

14. Oscillation Parameter Space LMA SMA LOW VAC

15. Solar Neutrinos in Super-K • The ratio of NC/CC cross section is ~1/6.5

16. Cherenkov Radiation Aircraft moves through air faster than speed of sound. Sonic Boom Sonic boom

17. Cherenkov Radiation When a charged particle moves through transparent media faster than speed of light in that media. Cone of light Cherenkov radiation

18. Super-K

19. Super-Kamiokande

20. 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

21. A muon going through the detector

22. A muon going through the detector

23. A muon going through the detector

24. A muon going through the detector

25. A muon going through the detector

26. A muon going through the detector

27. Stopping Muon

28. Stopping Muon – Decay Electron

29. Low Energy Electron in SK

30. 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

31. Solar Neutrinos

32. Energy Spectrum

33. Seasonal/Sunspot Variation

34. Day / Night - BP2000+New 8B SpectrumPreliminary

35. 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

36. 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

38. (Like SK)

39. SNO CC Results Fne= (35 ± 3 )% Fssm

40. 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

41. SNO Results (NC)

42. SNO Results (NC/CC) • SNO Results

43. SNO Results

44. Combined Results

45. Kamland – Terrestrial Neutrinos

46. Reactors Contributing to Kamland

47. Kamland Results (Dec. 2002)

48. Kamland

49. Kamland

50. All Experiments Combined with Kamland