1. Results and Prospects with the Sudbury Neutrino Observatory Neutrinos and SNO Phase III Results Low Threshold Analysis Future (maybe) Josh Klein University of Texas at Austin/ University of Pennsylvania

2. The Beam Spectra determined by nuclear physics, not solar model Starts out as pure e …

3. Solar Neutrino Disappearance  Before SNO experiments theory

4. National Geographic Solar Neutrino Appearance  SNO neutrino reactions on deuterons Neutrino-Electron Scattering (ES) Neutral Current (NC) Charged Current (CC)

5. SNO Neutrino Detection in D 2 O  CC and ES Electrons e-e- Cherenkov cone (+scattering) Neutrino-Electron Scattering (ES) Charged Current (CC)

6. SNO Neutrino Detection in D 2 O  Neutral current (NC) neutrons Neutral Current (NC) Phase I: Nov. 1999--May 2001 D 2 O only--- single 6.25 MeV  ray from n+d->t+ 

7. Phase I Signal Separation Likelihood fit to 9 1d pdfs  required assumptions about e energy spectrum Energy R 3 /R AV 3 cos  ¤ Position Energy Direction

8. SNO Neutrino Detection in D 2 O+NaCl  Neutral current (NC) neutrons Neutral Current (NC) Phase II: July 2001—Aug. 2003 n 36 Cl * 35 Cl 36 Cl  Higher capture , multiple  s, E=8.6 MeV

9. Phase II Signal Separation R 3 /R AV 3 Energy cos  ¤ Position Energy Direction  14 Isotropy (Correlation between E and  14 required 2D pdfs)

10. CC events Phase II Signal Separation  Extracted Spectrum But error bars large in part because of  =-0.52 anticorrelation between CC and NC

11. Solar Neutrino Appearance  SNO Phase I and Phase II Results

12. SNO Phase III  SNO neutrino detection with 3 He `NCDs’ Neutral Current (NC) NCD PMT x n

13. SNO Phase III Advantages: Break CC and NC signal correlation. Independent systematics from other Phases. Reduce 6.25-MeV  `contamination’ of CC and ES. Redundant measurements of NC in one Phase. Challenges: Added complexity. Signal rate low: ~2 NC neutrons/counter/month. `Just’ counting: few handles on particle ID. Putting backgrounds right into detector. Light loss (~10%) from absorption/scattering.

14. Chemical Vapor Deposition: Ni + 4CO Ni(CO) 4 Strong, ultrapure Ni shapes. Background alpha rate < best previous. Endcaps SNO Phase III  Counter Background Mitigation Counters also left to `cool down’ for ~2yrs underground  s are dominant background

15. SNO Phase III  Recapturing Lost Photons Overall gained back ~1/2 of losses Low noise backplane=lower thresholds

16. Events per 10 keV Neutrons from 24 Na:  + d  p + n 191 keV 573 keV 764 keV  Energy Spectrum from 3 He(n,p)t 191 573 p t n Ni wall 3 He:CF 4 gas Cu anode wire 573 191 SNO Phase III

17.  Counter Electronics - Data Acquisition Digital Scope Digital Scope Multiplexer (1 of 4) Current Preamp (1 of 40) 12 Input Channels / MUX Ionization current pulses digitized for detailed analysis. Currents integrated by analog circuits for precise, nearly deadtimeless, charge measurement. pulse spectrum SNO Phase III

18.  Neutron Efficiency Solar neutrinos produce neutrons uniformly in the D 2 O. Monte Carlo using Los Alamos “MCNP” code yields efficiency of 0.210(3). Time-series analysis of neutron bursts from 252 Cf fission confirms Monte Carlo precision. Neutron efficiency measured with uniform source: Dissolve 24 NaCl brine in the D 2 O, mix well. 15-hr 24 Na: 2.75-MeV  breaks up deuteron, liberates a neutron. SNO Phase III

19.  Cutting instrumental events Neutrons Alphas Reject Accept Sum of 10 strings Charge Amplitude 2 strings showed instrumental events that could not be completely cut from neutron/alpha events. Strings were dropped and PDFs were added in the analysis to allow for such events to be present on other strings. Neutron peak pos. 6 3 He strings in total were dropped from the analysis. SNO Phase III

20.  Neutron-capture spectrum (blind data) Energy (MeV) Counts per 10 keV 3 He(n,p) 3 H Alpha background SNO Phase III

21.  Simulations for Background Model SNO Phase III Microscopic model:  energy loss  energy straggling  multiple scattering Electron-ion pair generation Electron drift, diffusion Electron multiple scattering Ion mobility Electron avalanche Space charge Signal generation Electronics transfer function Calibration input: Po/bulk ratio Energy scale Energy resolution  depth Geometric effects

22. neutron signal alpha backgrounds: surface polonium decay bulk U and Th decay wire polonium decay wire bulk decay insulator polonium decay insulator bulk U and Th decay MC Energy (MeV) n Pulse Width ( n s) data Energy (MeV) SNO Phase III  Simulations of Pulse Shapes n Pulse Width ( n s)

23. Algorithm: Initial step i parameter guesses p i calculate likelihood L i Add random amounts to all parameters: p i+1 = p i + Norm(0,  i ) calculate likelihood L i+1 Keep p i or p i+1 : p keep =max(1, L i+1 / L i ) SNO Phase III  Final Signal Fits Need to simultaneously fit PMT+NCD data Should include systematic uncertainties (~50!) as nuisance parameters Markov Chain Monte Carlo

24. NC Signal: 983 ± 77 Neutron background: 185 ± 25 Alphas and Instrumental: 6126 ± 250 (0.4 to 1.4 MeV) SNO Phase III  Final Signal Fits---Counter Data

25. SNO Phase III  Final Signal Fits---Cherenkov Data

26. SourcePMT Events (neutrons  NCD Events (neutrons) D 2 O Radioactivity7.6 ± 1.228.7 ± 4.7 Atmospheric, 16 N 24.7 ± 4.613.6 ± 2.7 Other backgrounds0.7 ± 0.12.3 ± 0.3 NCD Bulk PD, 17,18 O( ,n) 4.6 +2.1 -1.6 27.6 +12.9 -10.3 NCD hotspots17.7 ± 1.864.4 ± 6.4 NCD cables1.1 ± 1.08.0 ± 5.2 External-source neutrons20.6 ± 10.440.9 ± 20.6 TOTAL77 +12 -10 185 +25 -22 SNO Phase III  Backgrounds

27.  SSM = 569(1±0.16) x 10 4 cm -2 s -1 (BSB05-OP: Bahcall, Serenelli, Basu Ap. J. 621, L85, 2005). Super-K: PRD 73, 112001, 2006 SNO Phase III  Flux Results Fluxes:

28. SNO only Solar Solar + 766 t-y KamLAND SNO Phase III  Mixing Parameters eV 2

29. Solar Measurements  Global Summary

30. What’s Next? “For 35 years people said to me: `John, we just don’t understand the Sun well enough to be making claims about the fundamental nature of neutrinos, so we shouldn’t waste time with all these solar neutrino experiments.’ Then the SNO results came out. And the next day people said to me, `Well, John, we obviously understand the Sun perfectly well! No need for any more of these solar neutrino experiments.’” ---John Bahcall, 2003

31. Forty Years of Monitoring the Core Thanks to O. Simard and SNO Using KamLAND mixing+Standard Solar Model (SSM uncertainties not included)

32. The Model  Mixing Summary 3 mixing angles 3 masses 1 phase (  ) +2 more phases if Only need 4  0 to describe all existing data Don’t know: Even one m i  13 any of the phases if New Parameters:

33. Testing the Model What predictions does the model make that we can check? L/E (or just L or just E) oscillation behavior Universality of the parameters (  m 2,  ) CP violation if  is non-zero and  13 big enough We have a model which has several parameters (masses, angles, phases) but not a whole lot of data that it explains… But neutrino oscillations give us a natural `interferometer’ Anything that distinguishes flavors (or mass states) alters the pattern

34. Neutrinos and Flavor Transformation Oscillations in Matter (MSW Effect) Entire Sun just treated as a potential term! Resonance when With

35. ReactorSolar E 2-10 MeV 0.1-15 MeV L150 km1.5 x 10 8 km MSW No Yes Anti- e e Only(?) Standard Model predicts these 2 experimental regimes see the same effect The First Precision Test KamLAND Collaboration Parameters appear universal Matter effect gets it right

36.    e   MSW (Matter Effect) Phenomenology Day/Night e Asymmetry Neutrinos and Flavor Transformation P ee EE hep-ph/0305159 Rise of survival probability at low T as we approach vacuum-average value of 1-(1/2)sin 2 2 

37. MSW Effect Signatures?  Solar Neutrino Day/Night Results Nope. A= 0.037±0.040 Super-Kamiokande SNO

38. MSW Effect Signatures?  Super-Kamiokande Spectrum Results Nope. CC events

39. Unlucky Parameters So far, it seems that Nature has picked out one of the few regions where we’d miss a direct MSW signature— `unlucky’ parameters Large spectral distortion Large Day/Night effect o Standard oscillation scenario makes explicit predictions o Oscillations provide a sensitive interferometer o s are cleanly sensitive to any sub-weak phenomena o Rich phenomenology available for exploring new physics So:

40. But is there any New Physics to Find Here? Or are we just left with measuring a few remaining parameters? Some possibilities: +Gravity `Sterile’ neutrinos +Dark Energy New interactions Ideas range from `exotic’ to `crazy’

41. Non-Standard MSW-like Effects Barger, Huber, Marfatia, PRL95, (2005) Miranda, Tortola, Valle, hep-ph/0406289 (2005) Friedland, Lunardini, Peña-Garay, PLB 594, (2004) M. C. Gonzalez- Garcia, P. C. de Holanda, E. Masso and R. Zukanovich Funchalc, hep-ph/0803.1180 Anything that distinguishes flavors (or mass states) alters the pattern

42. Going Further Going lower in energy tests MSW prediction Oscillation `interferometry’ sensitive to new physics And there are some interesting possibilities

43. SNO Goal: Energy Threshold T>3.5 MeV MSW Distortion biggest at low energies, as are NSI/MaVaNs Published Cherenkov world record: T>4.5 MeV (Super-K) Neutrino Survival Probability EE Charged Current: CC T e (MeV) Current SNO Threshold

44. T>3.5 MeV Why is this hard?  Find the ~3000 neutrino events: (Charged Current)

45. Cosmic rays < 3/hour Why is this hard?  Sources of Radioactivity

46. Why is this hard? E (MeV) Current SNO energy threshold We want to measure the shape of this spectrum Events can leak above energy threshold… (due to broad energy resolution)

47. Why is this hard? Radial distribution of backgrounds from outside volume D 2 O edge …or mis-reconstruct inside volume (PMT and H 2 O radioactivity much higher than D 2 O)

48. How to Go Lower? To make a meaningful measurement, we need: More signal statistics (Phase I+PhaseII~700 days) Lower backgrounds Smaller uncertainties This is a `war of attrition’. Need to re-make SNO’s entire analysis process, from the measurements of charge `pedestals’ to final fits to data

49.  SNO Neutrino Detection Lowering Radioactive Backgrounds What information do we get in a SNO `event’? Number of hit PMTs Total charge in each PMT Relative hit time of each PMT + understanding of detector Number of hit PMTs ~ num. photons ~ path length ~ energy Depends on PMT efficiencies, optical attentuation lengths, scattering, reflection coefficients…

50. Lowering Radioactive Backgrounds  Summary Improvement Tl/Bi reduced ~60% (MC) Improve energy resolution by using more PMT hits Remove events from outside volume with new cuts:  Does event look like a neutrino? R3R3 80% Reduction in Backgrounds From H 2 O Volume New

51. Reducing Systematic Uncertainties  Example: Energy Scale Number of hit PMTs ~ num. photons ~ path length ~ energy Depends on PMT efficiencies, optical attentuation lengths, scattering, reflection coefficients…

52. Reducing Systematic Uncertainties Want mapping of PMT hits  MeV known to better than 1%  Energy Scale Model everything: Calibrate everywhere: 16 N 6.1 MeV  -ray source  E ~ ±0.2% 16 N (Data-MC)/MC

53. Reducing Systematic Uncertainties cos  sun isotropy  Use neutrino data itself Allow systematics like energy scale to `float’ in fit to data So what? `Nuisance’ parameters are nothing new But: 19 signal+background pdfs >50 parameters No analytic model 3+1 dimensions Straightforward implementation would take ~1 year/fit

54. Reducing Systematic Uncertainties  Use neutrino data itself Solution: Build an analytic pdf out of gaussians (`kernel estimation’): To make it fast enough: 1 year  1 hour Lots of clever ideas+ 3D Graphics Card

55. Testing the PDFS  Compare Data to Simulation Radon `Spikes’ in Phase II

56. Significance = Expected MSW Sensitivity? But we’re actually doing better so far than we expected…

57. Expected Sensitivity? And there’s a bonus: NC statistics increased by 70% at lower threshold D 2 O+Salt (Phase I+II) provides additional CC/NC handle Breaks anticorrelation like Phase III Uncertainties lowered by work on systematics+correction Expect big improvement on NC precision (<5% ?) Results out end of Summer…

58. End-of-Run Last neutrino event: November 28, 2006 (ahead of schedule) November 29, 2006: Largest underground `earthquake’ (4.1) since before SNO began

59. End-of-Run  `Earthquake’ Damage

60. End-of-Run  Draining All 1000 (+100) tons of D 2 O now returned to Ontario Hydro

61. pep SNO CC/NC  m 2 = 8.0 × 10 −5 eV 2 tan 2  = 0.45 Future Possibilities stat + syst + SSM errors estimated  SNO+ Fill existing SNO detector with liquid scintillator to see even lower energy solar s `Collateral’ Physics: If enough 150 Nd can be dissolved in scintillator, can search for neutrinoless double beta decay Determine whether

62. Conclusions New Phase III SNO results agree well with Phase I+II Precision on mixing parameters improved More physics left to do in the solar sector Low threshold analysis may probe some of this More experiments and data on the way…

64. Angular distributions for ES in 3 Energy bins 6.5 - 7.0 MeV 6.0 - 6.5 MeV 7.0 - 7.5 MeV

65. Solar Measurements SAGE/GALLEX/GNOChlorine Super-K/SNO BOREXINO Inclusive Exclusive (`Realtime’)