1. J. Goodman Richtmyer Lecture – Jan. 2002 Richtmyer Lecture Neutrinos, Dark Matter and the Cosmological Constant The Dark Side of the Universe Jordan Goodman University of Maryland

2. J. Goodman Richtmyer Lecture – Jan. 2002 Outline Matter in the Universe Why do we care about neutrinos? Why do we think there is dark matter? Could some of it be neutrinos? The search for neutrino mass Type Ia Supernova and the accelerating Universe Dark Energy

3. J. Goodman Richtmyer Lecture – Jan. 2002 Seeing Big Picture

4. J. Goodman Richtmyer Lecture – Jan. 2002 The early periodic table

5. J. Goodman Richtmyer Lecture – Jan. 2002 The structure of matter 1889 - Mendeleyev – grouped elements by atomic weights

6. J. Goodman Richtmyer Lecture – Jan. 2002 The structure of matter (cont.) This lead eventually to a deeper understanding Eventually this led to Our current picture of the atom and nucleus

7. J. Goodman Richtmyer Lecture – Jan. 2002 What are fundamental particles? We keep finding smaller and smaller things

8. J. Goodman Richtmyer Lecture – Jan. 2002 Our current view of underlying structure of matter P is uud N is udd   is ud k  is us and so on… The Standard Model } Baryons } Mesons (nucleons)

9. J. Goodman Richtmyer Lecture – Jan. 2002 Facts about Neutrinos Neutrinos are only weakly interacting Interaction length is ~1 light-year of steel 40 billion neutrinos continuously hit every cm 2 on earth from the Sun (24hrs/day) 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

10. J. Goodman Richtmyer Lecture – Jan. 2002 Why do we care about neutrinos? Neutrinos –They only interact weakly –If they have mass at all – it is very small 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!

11. J. Goodman Richtmyer Lecture – Jan. 2002 The Ultimate Fate of the Universe   measures the total energy density of the Universe –If   > 1 Universe is closed –If   < 1 Universe is open   = 1 Universe (E tot =0) - Flat universe From the mass of the stars we get    Theorists say    What is the other 99.5% of the Universe?

12. J. Goodman Richtmyer Lecture – Jan. 2002 Why do we think there is dark matter? Isn’t obvious that most of the matter in the Universe is in Stars? Spiral Galaxy

13. J. Goodman Richtmyer Lecture – Jan. 2002 Why do we think there is dark matter? In a gravitationally bound system out past most of the mass V ~ 1/r 1/2 We can look at the rotation curves of other galaxies –They should drop off But they don’t!

14. J. Goodman Richtmyer Lecture – Jan. 2002 Why do we think there is dark matter? There must be a large amount of unseen matter in the halo of galaxies –Maybe 20 times more than in the stars! –Our galaxy looks 30 kpc across but recent data shows that it looks like it’s 200 kpc across

15. J. Goodman Richtmyer Lecture – Jan. 2002 Measuring the energy in the Universe We can measure the mass of clusters of galaxies with gravitational lensing These measurements give  mass ~0.3 We also know (from the primordial deuterium abundance) that only a small fraction is nucleons  nucleons < ~0.05 Gravitational lensing

16. J. Goodman Richtmyer Lecture – Jan. 2002 What is this ghostly matter? Could it be neutrinos? How much neutrino mass would it take? –Proton mass is 938 MeV –Electron mass is 511 KeV A neutrino mass of only 2eV would solve the galaxy rotation problem – 6 eV would close the Universe

17. J. Goodman Richtmyer Lecture – Jan. 2002 Does the neutrino have mass?

18. J. Goodman Richtmyer Lecture – Jan. 2002 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

19. J. Goodman Richtmyer Lecture – Jan. 2002 Neutrino Oscillations 1 2 =Electron Electron 1 2 =Muon Muon

20. J. Goodman Richtmyer Lecture – Jan. 2002 Super-Kamiokande

21. J. Goodman Richtmyer Lecture – Jan. 2002 Super-Kamiokande

22. J. Goodman Richtmyer Lecture – Jan. 2002 Super-Kamiokande

23. J. Goodman Richtmyer Lecture – Jan. 2002 Super-K Huge tank of water shielded by a mountain in western Japan –50,000 tons of ultra clean water –11,200 20in diameter PMTs –Under 1.5km of rock to reduce downward cosmic rays (rate of muons drops from ~100k/sec to ~2/sec) 100 scientists from US and Japan Data taking began in 1996

24. J. Goodman Richtmyer Lecture – Jan. 2002 Super-K site

25. J. Goodman Richtmyer Lecture – Jan. 2002 Super-K site Mozumi

26. J. Goodman Richtmyer Lecture – Jan. 2002 How do we see neutrinos? muon   electron e e-

27. J. Goodman Richtmyer Lecture – Jan. 2002 Cherenkov Radiation Boat moves through water faster than wave speed. Bow wave (wake)

28. J. Goodman Richtmyer Lecture – Jan. 2002 Cherenkov Radiation Aircraft moves through air faster than speed of sound. Sonic boom

29. J. Goodman Richtmyer Lecture – Jan. 2002 Cherenkov Radiation When a charged particle moves through transparent media faster than speed of light in that media. Cherenkov radiation Cone of light

30. J. Goodman Richtmyer Lecture – Jan. 2002 Detecting neutrinos Electron or muon track Cherenkov ring on the wall The pattern tells us the energy and type of particle We can easily tell muons from electrons

31. J. Goodman Richtmyer Lecture – Jan. 2002 A muon going through the detector

32. J. Goodman Richtmyer Lecture – Jan. 2002 A muon going through the detector

33. J. Goodman Richtmyer Lecture – Jan. 2002 A muon going through the detector

34. J. Goodman Richtmyer Lecture – Jan. 2002 A muon going through the detector

35. J. Goodman Richtmyer Lecture – Jan. 2002 A muon going through the detector

36. J. Goodman Richtmyer Lecture – Jan. 2002 A muon going through the detector

37. J. Goodman Richtmyer Lecture – Jan. 2002 A muon going through the detector

38. J. Goodman Richtmyer Lecture – Jan. 2002 Stopping Muon

39. J. Goodman Richtmyer Lecture – Jan. 2002 Stopping Muon – Decay Electron

40. J. Goodman Richtmyer Lecture – Jan. 2002 Neutrino Production Ratio predicted to ~ 5% Absolute Flux Predicted to ~20% :

41. J. Goodman Richtmyer Lecture – Jan. 2002 Atmospheric Oscillations about 13,000 km about 15 km Neutrinos produced in the atmosphere We look for transformations by looking at s with different distances from production SK

42. J. Goodman Richtmyer Lecture – Jan. 2002 Atmospheric Neutrino Interactions Reaction Thresholds Electron: ~1.5 MeV Muon: ~110 MeV Tau: ~3500 MeV Charged Current Neutral Current e  e n p W +

43. J. Goodman Richtmyer Lecture – Jan. 2002 Telling particles apart MuonElectron

44. J. Goodman Richtmyer Lecture – Jan. 2002 Muon - Electron Identification PID Likelihood sub-GeV, Multi- GeV, 1-ring Monte Carlo (no oscillations) We expect about twice as many  as e

45. J. Goodman Richtmyer Lecture – Jan. 2002 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 Also E vis < 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

46. J. Goodman Richtmyer Lecture – Jan. 2002 Low Energy Sample No Oscillations Oscillations (1.0, 2.4x10 -3 eV 2 )

47. J. Goodman Richtmyer Lecture – Jan. 2002 Moderate Energy Sample

48. J. Goodman Richtmyer Lecture – Jan. 2002 Multi-GeV Sample Oscillations (1.0, 2.4x10 -3 eV 2 ) No Oscillations  to  neutrino oscillations UP going DownUPDown

49. J. Goodman Richtmyer Lecture – Jan. 2002 Multi-Ring Events

50. J. Goodman Richtmyer Lecture – Jan. 2002 Upward Going Muons

51. J. Goodman Richtmyer Lecture – Jan. 2002 Summary of Atmospheric Results Best Fit for  to  Sin 2 2  =1.0,  M 2 =2.4 x 10 -3 eV 2  2 min =132.4/137 d.o.f. No Oscillations  2 min =316/135 d.o.f. 99% C.L. 90% C.L. 68% C.L. Best Fit Compelling evidence for  to  atmospheric neutrino oscillations

52. J. Goodman Richtmyer Lecture – Jan. 2002 Tau Appearance? 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

53. J. Goodman Richtmyer Lecture – Jan. 2002 The Solar Neutrino Problem

54. J. Goodman Richtmyer Lecture – Jan. 2002 Solar Neutrinos in Super-K The ratio of NC/CC cross section is ~1/6.5 W e - e e - e - Charged Current (electron ’s only)

55. J. Goodman Richtmyer Lecture – Jan. 2002 Solar Neutrinos in Super-K Super-K measures: –The flux of 8 B 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%)

56. J. Goodman Richtmyer Lecture – Jan. 2002 Solar Neutrinos From SunToward Sun

57. J. Goodman Richtmyer Lecture – Jan. 2002 Energy Spectrum

58. Day / Night - BP2000+New 8 B Spectrum Preliminary

59. J. Goodman Richtmyer Lecture – Jan. 2002 Seasonal/Sunspot Variation

60. J. Goodman Richtmyer Lecture – Jan. 2002 Combined Results e to  SK+Gallium+Cholrine exp’s- 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

62. J. Goodman Richtmyer Lecture – Jan. 2002 SNO Results - Summer 2001 SNO measures just e SK measures mostly e but also other flavors (~1/6 strength) From the difference we see oscillations! } This is from  &  neutral current

63. J. Goodman Richtmyer Lecture – Jan. 2002 Combining SK and SNO SNO measures just electron neutrinos and gets  e = (35% ± 3%)  ssm This implies that    ssm (~2/3 have oscillated) SK measures  es =(  e + (    /6.5) Assuming osc. SNO predicts that SK will see  es ~ (35%+ 65%/6.5)  ssm = 45% ± 3%  ssm SK observes:

64. J. Goodman Richtmyer Lecture – Jan. 2002 Neutrinos have mass Oscillations imply neutrinos have mass! We can estimate that neutrino mass is probably <0.2 eV – (we measure  M 2 ) Neutrinos can’t make up much of the dark matter – But they can be as massive as all the visible matter in the Universe! ~ ½ % of the closure density

65. J. Goodman Richtmyer Lecture – Jan. 2002 Supernova Cosmology Project Set out to directly measure the deceleration of the Universe Measure distance vs brightness of a standard candle (type Ia Supernova) The Universe seems to be accelerating! Doesn’t fit Hubble Law (at 99% c.l.)

66. J. Goodman Richtmyer Lecture – Jan. 2002 Energy Density in the Universe    may be made up of 2 parts a mass term and a “dark energy” term (Cosmological Constant)    mass  energy Einstein invented to keep the Universe static He later rejected it when he found out about Hubble expansion He called it his “biggest blunder” m   

67. J. Goodman Richtmyer Lecture – Jan. 2002 What is the “Shape” of Space? Open Universe   <1 –Circumference (C) of a circle of radius R is C > 2  R Flat Universe   =1 – C = 2  R – Euclidean space Closed Universe   >1 – C < 2  R

68. J. Goodman Richtmyer Lecture – Jan. 2002 Results of SN Cosmology Project The Universe is accelerating The data require a positive value of “Cosmological Constant” If    =1 then they find   ~ 0.7 ± 0.1

69. J. Goodman Richtmyer Lecture – Jan. 2002 Accelerating Universe

70. J. Goodman Richtmyer Lecture – Jan. 2002 Accelerating Universe

71. J. Goodman Richtmyer Lecture – Jan. 2002 Measuring the energy in the Universe Studying the Cosmic Microwave radiation looks back at the radiation from the “Big Bang”. This gives a measure of  0

72. J. Goodman Richtmyer Lecture – Jan. 2002 Latest Results - May 2001 2001 Boomerang Results  0 =1  nucleon mass from clusters

73. J. Goodman Richtmyer Lecture – Jan. 2002 What does all the data say? Three pieces of data come together in one region   ~ 0.7  m ~ 0.3 (uncertainty  ~0.1) Universe is expanding & won’t collapse Only ~1/6 of the dark matter is ordinary matter (baryons) A previously unknown and unseen “dark energy” pervades all of space and is causing it to expand

74. J. Goodman Richtmyer Lecture – Jan. 2002 What do we know about “Dark Energy” It emits no light It acts like a large negative pressure P x ~ -  x It is approximately homogenous –At least it doesn’t cluster like matter Calculations of this pressure from first principles fail miserably – assuming it’s vacuum energy you predict a value of  ~ 10 120 Bottom line – we know very little!

75. J. Goodman Richtmyer Lecture – Jan. 2002 Conclusion  tota l = 1 ± 0.04 –The Universe is flat! The Universe is : ~1/2% Stars ~1/2% Neutrinos ~33% Dark Matter (only 5% is ordinary matter) ~66% Dark Energy We can see ~1/2% We can measure ~1/2% We can see the effect of ~33% (but don’t know what most of it is) And we are pretty much clueless about the other 2/3 of the Universe There is still a lot of Physics to learn!

76. J. Goodman Richtmyer Lecture – Jan. 2002 Md Students at Super-K

77. J. Goodman Richtmyer Lecture – Jan. 2002 Super-K Disaster - Nov 11, 2001 Chain reaction destroyed 7000 OD and 1000 ID Tubes The cause is not completely understood, but it started with a lower pmt collapse. The energy release comes from a 4 T column of water falling There are plans to rebuild…

78. J. Goodman Richtmyer Lecture – Jan. 2002 Disaster (Continued)

79. J. Goodman Richtmyer Lecture – Jan. 2002 Disaster (Continued)