What Have We Learned from Super-K? Before Super-K SK-I (1996-2001) Atmospheric Solar SNO & SK-I

1. What Have We Learned from Super-K? • Before Super-K • SK-I (1996-2001) • Atmospheric • Solar • SNO & SK-I • Active solar • SK Accident • Rebuild Greg Sullivan University of Maryland

2. Why Super-Kamiokande? • Solar Neutrinos “Problem” • 3 experiments showed a deficit of solar neutrinos. • Going back ~30 years • About ½ of the expected number were observed • results can not be reconciled with the standard solar model • Atmospheric Neutrino “Anomaly” • IMB and Kamiokande saw less than expected ratio of nm/ne • One Proposed Explanation was: Neutrino Oscillations • Solar neutrinos might be ne -> nm • Atmospheric neutrinos might be nm -> nt

3. Neutrino Oscillations • If neutrinos oscillatethen “mixing” must occur between different type of neutrinos. Weak eigenstates of the neutrino are mixtures of the neutrinos with definite mass. • n mass is not 0 and flavor is not absolutely conserved! • Probability of electron neutrino to remain electron flavor • Matter Effects will alter this vacuum expression • MSW effect

4. Super-Kamiokande Detector • Detector Characteristics • 41 m h x 39 m dia. • 50,000 ton (22,000 ton fiducial) • 11,200 20” PMTs inner detector • 1,850 8” PMTs anti-detector • 40% photo-cathode coverage

5. Super-Kamiokande

6. 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

7. A muon going through the detector

8. A muon going through the detector

9. A muon going through the detector

10. A muon going through the detector

11. A muon going through the detector

12. A muon going through the detector

13. Stopping Muon

14. Stopping Muon – Decay Electron

15. Atmospheric Neutrino Production Ratio predicted to ~ 5% Absolute Flux Predicted to ~20% :

16. about 15 km about 13,000 km Atmospheric Oscillations We look for n transformations by looking at ns with different distances from production SK Neutrinos produced in the atmosphere

17. n - e e + W n p Atmospheric Neutrino Interactions Reaction Thresholds Electron: ~1.5 MeV Muon: ~110 MeV Tau: ~3500 MeV Neutral Current Charged Current

18. Telling particles apart Muon Electron

19. Muon - Electron Identification PID Likelihood sub-GeV, Multi-GeV, 1-ring Monte Carlo (no oscillations) We expect about twiceas many nm as ne

20. Super-K Atmospheric Data Set • 1289.4 days of data (22.5 kilotons fiducial volume) • Data Set is divided into: • Single and Multi Ring events • Electron-like and Muon-like • Energy Intervals • 1.4 GeV< Evis >1.4 GeV • Also Evis< 400MeV (little or no pointing) • Fully or partially contained muons (PC) • Upward going muons - stopping or through going • Data is compared to Atmospheric Monte Carlo • Angle (path length through earth) • Visible energy of the Lepton

21. Low Energy Sample No Oscillations Oscillations (1.0, 2.4x10-3eV2)

22. Moderate Energy Sample

23. Multi-GeV Sample No Oscillations Oscillations (1.0, 2.4x10-3eV2) Down UP Down UP going

24. Multi-Ring Events

25. Upward Going Muons

26. Summary of Atmospheric Results Compelling evidence for nm to nt atmospheric neutrino oscillations Best Fit for nmto nt Sin22q =1.0, DM2=2.4 x 10-3eV2 c2min=132.4/137 d.o.f. No Oscillations c2min=316/135 d.o.f. 99% C.L. 90% C.L. 68% C.L. Best Fit

27. Tau vs Sterile Neutrino Analysis

28. Tau’s require greater than 3 GeV in neutrino energy This eliminates most events Three correlated methods were used All look for enhanced upward going multi-ring events All show slight evidence for Tau appearance None are statistically significant Tau Appearance?

29. The p0 sample • For nmto ns the rate of NC events is reduced as compared to nmto nt which is the same as no oscillations. • The SK NC enriched sample is only about 1/3 from NC interactions. • The p0 sample is the cleanest NC signal • Until K2K the error in s(p0)(~1-2 Gev) has been as large as the effect!

30. p0Peaks

31. New Results

32. Neutrinos From Solar Reactions

33. The Solar Neutrino Problem

34. Oscillation Parameter Space LMA SMA LOW VAC

35. Expected Day – Night Asymmetry Bahcall

36. n e - e - W n - e e Charged Current n (electron ’s only) Solar Neutrinos in Super-K • The ratio of NC/CC cross section is ~1/6.5

37. Solar Neutrinos in Super-K • Super-K measures: • The flux of 8B solar neutrinos (electron type) • Energy, Angles, Day / Night rates, Seasonal variations • Super-K Results: • We see the image of the sun from 1.6 km underground • We observe a lower than predicted flux of solar neutrinos (45%)

38. Low Energy Electron in SK

39. Solar Neutrinos SSM: Bachall 2000 Flux: 8B 5.05x106 /cm2/s Spectrum Ortiz et al Toward Sun From Sun

40. Global Flux allowed parameter space

41. Energy Spectrum

42. Energy Spectrum

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

44. Seasonal Variation

45. Combined Results

47. SNO measures just ne SK measures mostly ne but also other flavors (~1/6 strength) From the difference we see oscillations! This is from nm & nt neutral current } SNO Results - Summer 2001

48. 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

49. SK & SNO Flux Measurements

50. Super-K Disaster - Nov 12, 2001 • Chain reaction destroyed 7000 ID and 1000 OD Tubes • The cause is not completely understood, but it started with a bottom pmt collapse. • The energy release comes from a 4 T column of water falling • There are plans to rebuild…