Results from Sudbury Neutrino Observatory

1. Results from Sudbury Neutrino Observatory Huaizhang Deng University of Pennsylvania

2. The SNO Collaboration Canada Carleton University Laurentian University Queen’s University TRIUMF University of British Columbia University of Guelph University of Oxford Rutherford Laboratory/ University of Sussex Brookhaven National Laboratory Lawrence Berkeley National Laboratory Los Alamos National Laboratory University of Pennsylvania University of Texas at Austin University of Washington U.K. U.S.A.

3. Outline • Overview of SNO experiment • Solar neutrino results from phase I and II • Nucleon decay limit • Antineutrino search • Status of phase III

4. Solar neutrinos

5. The Sudbury Neutrino Observatory • 2092 meters deep underground • 1000 tons of ultrapure D2O • in a 12 meter diameter • acrylic vessel • 7000 tons of ultrapure H2O • as shield • 9500 PMTs mounted on a • 18 meter diameter frame • 40 helium proportional counters • with total length of 398 m

6. Goals of SNO • Solar Neutrinos: • Measure mixing parameters, especially θ12. • Search for direct signatures of neutrino oscillation. • Day – Night Asymmetry • Spectral Distortions. • Rare solar neutrino searches. • Solar Antineutrinos • Neutrinos from the hep reaction. • Other Physics: • Atmospheric Neutrino • Proton Decay • Neutron – Antineutron Oscillations. • Supernovae.

7. Neutrino interaction in SNO e− Only e , Good measurement of E , Weak angle correlation 1-1/3cos⊙ e− • e + 0.154(μ+) , Some energy information Strong angle correlation Low statistics n • e + μ+  , No angle and energy information after thermalization

8. D2O phase (November 1999 – May 2001) Radial Distribution (R3, RAV=1) Energy Distribution (MeV) Model dependent Solar Direction Distribution

9. Salt phase (July 2001 – September 2003) Radial Distribution (R3, RAV=1) NC Changed due to larger σ Energy Distribution (MeV) Model dependent NC Shifted to higher energy Solar Direction Distribution Unchanged Isotropy Distribution All new due to multiple ’s

10. Phase III (December 2003 – 2006) n or g, E > 2.2 MeV n 2H p 3He p t PMTs NCDs • Neutrons can be detected besides • through Čerenkov light events. • Reduce the correlation between NC • and CC measurements.

11. Backgrounds • Instrumental backgrounds • Low energy ’s and ’s from U and Th decay chain • misrecontruction • energy resolution • Neutrons • photodisintegration of deutrons by ’s • cosmic ray muons • Atmospheric neurtinos • (,n) processes • natural fission • anti-neutrinos • ’s (proportional counter only)

12. Measuring low energy background Fit to the low energy events with Rn in D2O The low energy background Add Rn in D2O (unmixed) Add Rn in D2O (mixed)

13. Signal extraction in salt phase Isotropy radius direction energy

14. Neutrino flux results D2O phase salt phase (unit 106/cm2/s)

15. Oscillation parameters • Maximal mixing is excluded by 5.4σ • LMA I only at >99%

16. Nucleon decay limit R R R RNC RNC • The invisible (N3) nucleon decay in 16O produce the de-excitation ’s • For vanishing neutron, BR(E=6.18MeV)=44% and BR(E=7.03MeV)=2% • For vanishing proton, BR(E=6.32MeV)=41% and BR(E=7.0 MeV)=4% RandRNCdidn’t change while other parameters changed from D2O phase to salt phase R For neutron modes : inv > 1.9 × 1029 year For proton modes : inv > 2.1 × 1029 year (Phys. Rev. Lett. 92, 102004, 2004)

17. Electron antineutrino search Flux (cm-1s-1MeV-1) Differential limit • Integral limit at 90% CL: • Ф < 3.4 × 104 cm-2s-1 E (MeV)

18. From phase II to phase III 5 cm Cu anode wire (50 m) 3He-CF4 gas mix Length of NCD Strings: 911 m Fused silica insulator CVD nickel counter body (0.36 mm thick) Delay line termination Vectran braid Acrylic ROV ball Acrylic anchor ball 8/28/2003 end of salt phase start salt removal 10/3/2003 end of salt removal start 2nd D2O phase 3He 4He 10/27/2003 end of 2nd D2O phase old optics restored start deployment of proportional counters N 12/3/2003 first counter deployed 2/12/2004 last counter deployed 4/23/2004 removal of deployment equipment, start phase III commissioning 10/??/2004 start of production data taking of phase III

19. Data from proportional counters neutron with p-t track  wire 1.5 current n or g, E > 2.2 MeV 1.0 n 0.5 2H 0.0 -0.5 p 3He p t 0 2 4 6 8 Time (μs) a track  wire Microdischarge current 20 current 80 15 60 10 40 5 20 0 0 0 1 2 3 4 5 Time (μs) 0 2 4 6 8 10 Time (μs) a b, g • p and t have total energy 764 keV • neutron produces two particles • while background has only one • particle • backgrounds come from wall • 4He string provides pure background

20. Conclusions • Measure the 8B solar  flux without assumption about • energy dependence of neutrino survival probability • Restrict the mixing parameters, and exclude maximal • mixing in solar sector • New limit on invisible nucleon decay • Commissioning helium proportional counter system • Will run for 2.5 years with helium proportional counters.

22. Solar neutrino oscillation e e x x W + Z e e e e Flavor eigenstates are not mass eigenstates : In vacuum In matter

23. Solar neutrino problem