Past Neutrino Mass & Oscillations Present Atmospheric neutrinos Solar neutrinos Future

1. Solar & Atmospheric Oscillation Experiments Greg Sullivan University of Maryland Aspen Winter ConferenceJanuary 21, 1999 • Past • Neutrino Mass & Oscillations • Present • Atmospheric neutrinos • Solar neutrinos • Future n ?? e

2. Can we detect them? • In 1934 Bethe & Peierls calculated the cross section for neutrino interaction of 10-44cm2. • Nature (London) 133, 532(1934) “It is therefore absolutely impossible to observe processes of this kind with neutrinos created in nuclear transformations” “… one can conclude that there is no practically possible way of observing the neutrino.” “… and it is not necessary to assume interaction in order to explain the function of the neutrino nuclear transformations ...” • In fact, it was some 20 years before they were detected using a nuclear reactor as a source.

3. Solar Neutrino Spectrum

4. Solar Neutrinos detected • R. Davis and his 37Cl detector • same principle used to try and detect antineutrinos from a nuclear reactor in 1955. • measured the flux of neutrinos from the sun almost continuously since about 1970!

5. Solar Neutrino Rate in Cl Detector is 1/3-1/2 expected Explanations? • Astrophysics - Standard Solar Model • Neutrinos from 7Be and 8B • Very sensitive to Sun’s core temperature • Particle Physics Solutions --- Neutrino properties are not what we think! • Electron Neutrinos don’t make it to earth • Magnetic properties of n • ne change flavor in transit - Neutrino Oscillations! • Non zero neutrino mass! • Lepton flavor mixing!

6. Neutrino Mass & Neutrino Oscillations? • What is the mass of the neutrino? • Is it identically zero? • If not, Why is it so small? see-saw mechanism

7. Neutrino Oscillations • If n mass is not 0 and flavor is not absolutely conserved then “mixing” may occur between different type of neutrinos. Weak eigenstates of the neutrino are mixtures of the neutrinos with definite mass.

8. Solar Neutrino Experiments • Homestake - Radiochemical • Huge tank of Cleaning Fluid • ne + 37Cl e- + 37Ar • Mostly 8B neutrinos + some 7Be • 30 years at <0.5 ev/day • 1/3 SSM • 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

9. Summary of Results Before Super-K • Four experiments measured versus predicted from solar model

10. BP95 FROM Langacker -Allowed regions at 95% CL from individual experiments and from the global fit. The Earth effect is included for both time-averaged and day/night asymmetry data, full astrophysical and nuclear physics uncertainties and their correlations are accounted for, and a joint statistical analysis is carried out. The region excluded by the Kamiokande absence of the day/night effect is also indicated.

11. Atmospheric Neutrinos Ratio predicted to ~ 5% Absolute Flux Predicted to ~20% : • primary CR spectrum • geomagnetic cutoff • hadron production modeled from accelerator data

12. Atmospheric Neutrino Anomaly • The Observed Ratio of nm/ne is too low • Produced when pions generated in the upper atmosphere by cosmic rays decay. • Predicted Ratio of nm/ne ~ 2 • Observed Ratio is ~ 1 • Particle Physics Solutions --- Neutrino properties are not what we think! • Muon Neutrinos don’t make it to earth • nm change flavor in transit - Neutrino Oscillations! • Non zero neutrino mass! • Lepton flavor mixing!

13. Worldwide Results on “R”Before Super-Kamiokande

14. Two Suggestions of Neutrino Transformation • Solar Neutrinos (~1-15 Mev ne) • Davis experiment (Cl) saw ~30% of expected flux of nefrom 8B & 7Be • Galium experiments showed less than expected flux of ne from all processes • Kamiokande saw ~40% nefrom 8B • These results can not be reconciled with the standard solar model • Atmospheric Neutrinos (~.1 - 3 GeV) • IMB and Kamiokande saw less than expected ratio of nm/ne • One Proposed Explanation was: Neutrino Oscillations • Solar neutrinos might be ne nm • Atmos. neutrinos might be nm nt

15. Super-KamiokandeThe Next generation Underground Neutrino Detector. Super-Kamiokande is a 50,000 ton water Cerenkov detector at a depth of 1000 meters in the Kamioka Mozumi mine in Japan. • Detector Characteristics • 41 m h x 39 m dia. • 50,000 tonne total/22,000 tonne fiducial • 11,200 20” PMTs inner detector • 1,850 8” PMTs anti-detector • 40% photocathode coverage • Trigger Threshold ~5 MeV • Resolution • Energy 16%/(E)1/2 at 10 MeV • Position ~50 cm at 10 MeV • Angular ~30 degrees at 10 MeV

16. SuperKamiokandeCollaboration • Institute for Cosmic Ray Research, University of Tokyo • Gifu University • Institute for Nuclear Study, University of Tokyo • National Laboratory for High Energy Physics, KEK • Kobe University • Miyagi Education University • Niigata University • Osaka University • Tokai University • Tohoku University • Tokyo Institute of Technology • Boston University • Brookhaven National Laboratory • University of California, Irvine • California State University, Dominguez Hills • Cleveland State University • George Mason University • University of Hawaii • Los Alamos National Laboratory • Louisiana State University • University of Maryland • State University of New York, Stony Brook • University of Warsaw • University of Washington

17. The Super-K Detector

18. The Super-Kamiokande Tank During Filling in 1996

19. Stopping Muon

20. Electron from decay of stopping muon

21. Muon - Electron Identification

22. Sub-Gev (535 days)Evis < 1.33 GeVPe > 100 MeV/cPm> 200 MeV/c

23. Multi-Gev (535 days)Evis > 1.33 GeV Fully Contained Partially Contained

24. Worldwide Results on “R” • Detectors continue to run • MACRO upward going muons • Soudan II • Super-K muons

25. If the muon n‘s oscillate, what it look like? • Depletion of nm relative to ne • “double ratio” R • L dependence of nmflux • Zenith angle dependence

26. Zenith Angle Dependence

27. Zenith Angle Dependence

28. Zenith Angle Dependence

29. L/E Distribution of Atmospheric Neutrinos The dashed lines show the expected shape for nmntat Dm2=2.2 x 10-3 eV2 and sin2 2q = 1.

30. Atmospheric Results

31. East-West Effect

32. Zenith Angle Distribution(736 Day Sample)

33. Zenith Angle Dependence(736 day sample)

34. MACRO Detector • Data collected ‘89 - Dec ‘97 • ~3 live-years with 6 full SM • ~480 Upward Going Muon events R(data/MC)= 0.74  .036sta.046sys.13theo • Probability for no oscillations P(null) = 14% • Best fit mass assuming maximal mixing: Dm2 ~ 2 x 10-3 eV2

35. MACRO upward-going muons • Probabilities Number + Shape • Probability of no oscillations P(null)  0.1% • Best fit oscillation parameters sin22q = 1.0 , Dm2 2 x 10-3 eV2 P(best fit)  17%

36. A Picture of the Sun using Neutrinos in Super-K

37. 10 MeV Electron in Super-K

38. Super Low Energy (SLE) Data

39. Solar Neutrino Flux(New 708 Day Sample)

40. Day-Night Results708 day Sample

41. Energy Spectrum708 day + 419 day SLE

42. Spectrum and Oscillations? • Data favors Vacuum solution (red) • small angle MSW (blue) starting to get squeezed by flatness with SLE data

43. Hep Neutrinos ? • Set limit on hep flux from data • integral of events between Ethres & Eend • Ethres= 17 MeV , Eend= 25MeV Hep flux < 8 SSM at 90% C.L. • Ethres= 19 MeV , Eend= 20 MeV Hep flux < 20 SSM at 90% C.L.

44. Seasonal Variation

45. Energy Dependence of Seasonal Variation for Just-so solution

46. Seasonal Variation in High Energy Data

47. Summary of Super-K Results • Atmospheric Neutrinos • Strong Evidence for nm nt (ns) Oscillations • New results consistent • Higher statistics may allow separation of (nt )(ns) • Solar Neutrinos • No evidence for Day/Night Effect • Squeezes Large Angle Solution • Super Low E and more statistics somewhat flattens energy spectrum • Starting Squeeze Small Angle Solution • Vacuum (Just-So) solution is still alive • Continue to Run • Postponed the scheduled June ‘99 shutdown

49. Future ~2000 • Atmospheric Neutrinos • Continued running of Super-Kamiokande • Neutral Currents ? • Distinguish nmnt from nmns • MACRO muons & neutrinos • Soudan II • KEK to Super-K (K2K) • Solar Neutrinos • Spectral Distortion at High Energy • Instrumental Effect? • Energy Scale & Resolution LINAC limitations • D-T Generator to make 16N as calibration source (NSF) • Hep Neutrinos? • Need 20 times predicted flux • Use Super-K data >18 MeV to set limit on hep flux?? • Statistics? • Seasonal Variation needs more data

50. Future 2000+ • Atmospheric Neutrinos • Accelerator Experiments (FNAL, CERN, KEK) • Known Neutrino Direction • Better Neutrino Energy Measurement • Appearance Experiment ?? • Solar Neutrinos • Continued Super-Kamiokande Running • New Experiments Soon - should settle the solar neutrino problem • Sudbury Neutrino Observatory (SNO) • Canada,US,UK 11 institutions • Fill Apr, 98 -- Feb, 99 ? • 6 mo. Debug & Calibration • 1 Yr. pure D2O • Borexino • ICARUS