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Unraveling the Mysteries of Neutrinos, Dark Matter & Cosmology

Explore the significance of neutrinos, dark matter, and the cosmological constant in understanding the dark side of the universe. Delve into topics like neutrino mass, dark energy, and the accelerating universe.

jessegregory
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Unraveling the Mysteries of Neutrinos, Dark Matter & Cosmology

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  1. Quarknet Symposium May 2003 Neutrinos, Dark Matter and the Cosmological Constant The Dark Side of the Universe Jordan Goodman University of Maryland

  2. Outline • 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 – Solar Neutrinos • Super-K • SNO • Kamland • The accelerating Universe - Dark Energy • SCP • WMAP

  3. Seeing Big Picture

  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. Facts about Neutrinos • 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

  6. Spiral Galaxy Why do we think there is dark matter? • Isn’t obvious that most of the matter in the Universe is in Stars?

  7. Why do we think there is dark matter? • In a gravitationally bound system out past most of the mass V ~ 1/r1/2 • We can look at the rotation curves of other galaxies • They should drop off But they don’t!

  8. 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

  9. We can measure the mass of clusters of galaxies with gravitational lensing These measurements give Wmass ~0.3 We also know (from the primordial deuterium abundance) that only a small fraction is nucleons Wnucleons < ~0.04 Measuring the energy in theUniverse Gravitational lensing

  10. Dark Matter

  11. Dark Matter

  12. 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 • Neutrino mass of 2eV would solve the galaxy rotation problem – 20eV would close the Universe • Theories say it can’t be all neutrinos • They have difficulty forming the kinds of structure observed. The structures they create are too large and form too late in the history of the universe

  13. n Does the neutrino have mass?

  14. 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

  15. Solar Neutrinos

  16. Super-Kamiokande

  17. Solar Neutrinos

  18. 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

  19. (Like SK)

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

  21. Combining SK and SNO • SNO measures Fne= (35 ± 3 )% Fssm • SK Measures Fes= (47 ± .5 ± 1.6)% Fssm • 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

  22. SNO Results (NC/CC) • SNO Results

  23. SNO Results

  24. Combined SK and SNO Results

  25. Kamland – Terrestrial Neutrinos

  26. Reactors Contributing to Kamland

  27. Kamland Results (Dec. 2002)

  28. Kamland

  29. Kamland

  30. All Experiments Combined with Kamland

  31. The Winner Solar Neutrino Conclusions • It looks like the Solar Neutrino problem has been solved! • All Data (except LSND) is now consistent with the large angle MSW solution – ne-> nm • We have ruled out SMA and Low solutions • Disfavor Sterile Neutrino solutions • Neutrinos have mass! • This confirms the atmospheric neutrino results • The Solar n mass difference ~0.003eV • Future Experiments – • MiniBoone – LSND effect

  32. 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

  33. Moderate Energy Sample

  34. Multi-GeV Sample

  35. 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 Now the most cited exp. HEP paper Skip Tau studies

  36. Neutrinos have mass • Oscillations imply neutrinos have mass! • We can estimate that neutrino mass is probably <0.2 eV – (we measure DM2) • 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

  37. Hubble Law

  38. The expanding Universe • The Universe is expanding • Everything is moving away from everything • Hubble’s law says the faster things are moving away the further they are away

  39. The expanding Universe

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

  41. The expanding Universe

  42. W0may be made up of 2 parts a mass term and a “dark energy” L term (Cosmological Constant) W0= Wmass + Wenergy Einstein invented L to keep the Universe static He later rejected it when he found out about Hubble expansion He called it his “biggest blunder” L m Energy Density in the Universe W0=1

  43. The Cosmological Constant

  44. What is the “Shape” of Space? • Closed Universe W0>1 • C < 2pR • Open Universe W0<1 • Circumference (C) of a circle of radius R is C > 2pR • Flat Universe W0=1 • C = 2pR • Euclidean space

  45. The Universe is accelerating The data require a positive value of L “Cosmological Constant” If W0=1 then they find WL~ 0.7 ± 0.1 Results of SN Cosmology Project

  46. Accelerating Universe

  47. Accelerating Universe

  48. Measuring the energy in the Universe • Studying the Cosmic Microwave radiation looks back at the radiation from 400,000 years after the “Big Bang”. • This gives a measure of W0

  49. W0=1Wnucleon Recent Results - 2002

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