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Dustmaids Down a Drafty Hall : Neutrinos at the Sudbury Neutrino Observatory

Dustmaids Down a Drafty Hall : Neutrinos at the Sudbury Neutrino Observatory. Joshua R. Klein. The University of Texas at Austin. Sambamurti Lecture, Brookhaven National Laboratory. Neutrinos The Sun Solar Neutrino Problem Sudbury Neutrino Observatory Results and the Future.

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Dustmaids Down a Drafty Hall : Neutrinos at the Sudbury Neutrino Observatory

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  1. Dustmaids Down a Drafty Hall: Neutrinos at the Sudbury Neutrino Observatory Joshua R. Klein The University of Texas at Austin Sambamurti Lecture, Brookhaven National Laboratory • Neutrinos • The Sun • Solar Neutrino Problem • Sudbury Neutrino Observatory • Results and the Future

  2. Two Stories

  3. Invention of the Neutrino Beta decay mystery: 2-body decay should give mono-energetic electron But observed spectrum is continuous

  4. Invention of the Neutrino Wolfgang Pauli suggests a third particle (1930) Designed to be impossible to detect…almost.

  5. Neutrino Poetry NEUTRINOS, they are very small. They have no charge and have no mass And do not interact at all. The earth is just a silly ball To them, through which they simply pass, Like dustmaids down a drafty hall Or photons through a sheet of glass. They snub the most exquisite gas, Ignore the most substantial wall, Cold shoulder steel and sounding brass, Insult the stallion in his stall, And scorning barriers of class, Infiltrate you and me! Like tall and painless guillotines, they fall Down through our heads into the grass. At night, they enter at Nepal and pierce the lover and his lass From underneath the bed-you call It wonderful; I call it crass. “Cosmic Gall”, by John Updike In Telephone Poles And Other Poems (1960)

  6. Detecting Neutrinos e- n • Weakly Interacting Signal

  7. Detecting Neutrinos n • Weakly Interacting Signal Add more matter…

  8. Detecting Neutrinos n n n n n n n n n n n n n eV keV MeV GeV TeV CNB Radioactive nuclei Reactors Supernovae Accelerators The Sun Atmospherics Cosmic sources • Weakly Interacting Signal Or use more neutrinos…

  9. Detecting Neutrinos m m m m m m m m m m • Backgrounds: Muons from Space

  10. Detecting Neutrinos • Backgrounds: Natural Radioactivity

  11. Discovery of the Neutrino Reines and Cowan see convincing signal in 1956

  12. `Standard Model’ Neutrinos • Come in three `flavors’ (ne, nm, nt) • Are massless • Interact weakly • Cannot change flavor Our best theory of the microscopic Universe… Neutrinos: Over twenty years of tests confirmed even The most subtle predictions.

  13. Solar Fusion • On the Other Hand…

  14. Solar Neutrino Spectra …within the `Standard Solar Model’

  15. Solar Neutrino Experiments Experiments need to be: • Big to detect weakly interacting n’s • Deep to get away from cosmic rays • Clean to reduce radioactivitiy

  16. Solar Neutrino Experiments Won Nobel Prize this year! First experiment by Davis et al in 1960’s Radiochemical Method (Chlorine): Found ~ 1/3 of expected rate!

  17. Solar Neutrino Experiments Water Cerenkov method: nx + e-nx +e-

  18. Solar Neutrino Experiments Water Cerenkov method: nx + e-nx +e- Only 50 detectable photons for each n interaction… …but photomultiplier tubes (PMTs) can see even 1 photon. • Experimentalists design • Detection electronics • Readout electronics and software • Analysis software…

  19. Solar Neutrino Experiments Water Cerenkov method: nx + e-nx +e- Water Cerenkov detectors see 1/2 of expected flux (1980’s and 1990’s)

  20. After Six Solar n Experiments • 3 Gallium (Radiochemical) • 1 Chlorine (Radiochemical) • Kamiokande + Super-Kamiokande (Water Cerenkov) What’s Going On?? • Are experiments wrong? • Or Solar Theory? • Or the neutrino?

  21. Introduction to n Oscillations “Most natural explanation for measurements” How can neutrinos change from one type to another? Particles have wavelike properties. and a nm is the sum of those two waves shifted relative to one another If a ne is the sum of two waves then a ne can change into a nm if Wave 1 (n1) travels at a different speed than Wave 2 (n2) This can happen if the neutrinos have different masses. And can be enhanced if n’s travel though dense matter.

  22. Oscillation Mechanism (Matter) ne nmconversion in matter nm ne regeneration in matter Little oscillation through vacuum ne ne nm nm ne nm nm • Day-Night asymmetry Night Day

  23. Evidence for Neutrino Oscillations `Atmospheric’ n’s in Kamiokande II, IMB, and Super-Kamiokande: Only half the number of nm’s coming upward

  24. The Story So Far • Solar n fluxes inconsistent with models • Oscillations provide a nice explanation • But unproven for solar n’s • Solar physics with n’s still on hold…

  25. Herb Chen’s Idea (1984): Use Heavy Water ES CC NC

  26. Sudbury Neutrino Observatory Main goal: Look directly for changed neutrinos!

  27. Where to put it? Sudbury, Ontario (Canada)

  28. The Sudbury Neutrino Observatory A collaboration of Chemists, Nuclear Physicists, and Particle Physicists United States Brookhaven Lab Los Alamos Lab LBL U. of Pennsylvania U. of Washington U. of Texas@Austin U.K. U. of Oxford Canada Carleton U. U. British Columbia U. of Guelph Laurentian U. Queens U.

  29. Sudbury Neutrino Observatory 1000 tonnes D2O Support Structure for 9500 PMTs, 60% coverage 12 m Diameter Acrylic Vessel 1700 tons Inner Shielding H2O 5300 tons Outer Shield H2O Urylon Liner and Radon Seal

  30. nDetection in D2O ES CC

  31. n Detection in D2O NC

  32. SNO Neutrinos • `Production Running’ (Nov 1999-)

  33. Other Physics High Energy Atmospheric n Traveling Through Earth

  34. Creighton Mine

  35. Sudbury Highlights

  36. Underground…

  37. …but in the Lab.

  38. Construction

  39. Data Processing What we got What we expected • Unexpected Effects! Predicted Raw Energy Spectrum Compared to Data Energy (MeVx8.5)

  40. Extraction Prerequisites Data Processing Remove backgrounds Reconstruct position and energy Background Measurement Determine remaining contamination Model Building For predicting no. v’s Signal Extraction Final fits to data Determine how many of each reaction

  41. Radioactive Backgrounds Cosmic rays < 3/hour

  42. Data Processing 450,188,649 events 2,928 events Apply cuts, fit position and direction, Kinetic energy > 5 MeV, R < 550 cm

  43. Model Building • How do we know how many we expect? Need to know how detector measures: • Energy • Position and direction • Particle type (e vs. g) Use radioactive sources: • 16N  6.13 MeV ’s • p,T  19.8 MeV ’s • Neutrons  6.25 MeV ’s • 8Li  ’s, E<14 MeV • Encapsulated U and Th sources

  44. Results Herb Chen’s original idea becomes possible: NC CC (sensitive only to ne) (sensitive to all flavors equally) Main Question: Is number of n’s measured with NC > CC??

  45. Signal Extraction SNO measurements: (units 106 cm-2 s-1) • Flux Measurements Total number of neutrinos much bigger than ne’s!

  46. Phase I (Pure D2O) Results • SNO Compared to Other Solar Expts.

  47. AE= Looking for the Matter Effect Do ne’s `regenerate’ during the night? Hard to say…so far.

  48. The Standard Model of Particle Physics So? Is the Standard Model Dead?

  49. The Standard Model + neutrino flavor transformation So? Is the Standard Model Dead?

  50. The Next Theory? So? Is the Standard Model Dead?

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