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Results and Future Challenges of the Sudbury Neutrino Observatory

Results and Future Challenges of the Sudbury Neutrino Observatory. Neil McCauley University of Pennsylvania WIN 2005 : Delphi, Greece. 7 th June 2005. Overview. The Sudbury Neutrino Observatory. Results from the Salt Phase. Future Challenges: Phase 3: 3 He Counters.

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Results and Future Challenges of the Sudbury Neutrino Observatory

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  1. Results and Future Challenges of the Sudbury Neutrino Observatory Neil McCauley University of Pennsylvania WIN 2005 : Delphi, Greece. 7th June 2005

  2. Overview • The Sudbury Neutrino Observatory. • Results from the Salt Phase. • Future Challenges: • Phase 3: 3He Counters. • Reducing the energy threshold in SNO. • Conclusions.

  3. The SNO Collaboration S.D. Biller, M.G. Bowler, B.T. Cleveland, G. Doucas, J.A. Dunmore, H. Fergani, K. Frame, N.A. Jelley, J.C. Loach, S. Majerus, G. McGregor, S.J.M. Peeters, C.J. Sims, M. Thorman, H. Wan Chan Tseung, N. West, J.R. Wilson, K. Zuber Oxford University E.W. Beier, H. Deng, M. Dunford, W. Frati, W.J. Heintzelman, C.C.M. Kyba, N. McCauley, M.S Neubauer, V.L. Rusu, R. Van Berg, P. Wittich University of Pennsylvania S.N. Ahmed, M. Chen, F.A. Duncan, E.D. Earle, H.C. Evans, G.T. Ewan, B. G Fulsom, K. Graham, A.L. Hallin, W.B. Handler, P.J. Harvey, C. Howard, L.L Kormos, M.S. Kos, C. Kraus, C.B. Krauss, A.V. Krumins, J.R. Leslie, R. MacLellan, H.B. Mak, J. Maneira, A.B. McDonald, B.A. Moffat, A.J. Noble, C. Ouellet, B.C. Robertson, P. Skensved, M. Thomson, Y. Takeuchi, A. Wright Queen’s University D.L. Wark Rutherford Appleton Laboratory R.L. Helmer TRIUMF A.E. Anthony, J.C. Hall, M. Huang, J.R. Klein, S. Seibert University of Texas at Austin T.V. Bullard, G.A. Cox, P.J. Doe, C.A. Duba, J.A. Formaggio, N. Gagnon, R. Hazama, M.A. Howe, S. McGee, K.K.S. Miknaitis, N.S. Oblath, J.L. Orrell, K. Rielage, R.G.H. Robertson, M.W.E. Smith, L.C. Stonehill, B.L. Wall, J.F. Wilkerson University of Washington C.W. Nally, S.M. Oser, T. Tsui, C.E. Waltham, J.Wendland University of British Columbia J. Boger, R.L. Hahn, R. Lange, M. Yeh Brookhaven National Laboratory A.Bellerive, X. Dai, F. Dalnoki-Veress, R.S. Dosanjh, D.R. Grant, C.K. Hargrove, L. Heelan, R.J. Hemingway, I. Levine, C. Mifflin, E. Rollin, O. Simard, D. Sinclair, N. Starinsky, G. Tesic, D. Waller Carleton University M. Bergevin,P. Jagam, H. Labranche, J. Law, I.T. Lawson, B.G. Nickel, R.W. Ollerhead, J.J. Simpson University of Guelph B. Aharmim J. Farine, F. Fleurot, E.D. Hallman, A. Krüger, S. Luoma, M.H. Schwendener, R. Tafirout, C.J. Virtue Laurentian University Y.D. Chan, X. Chen, C. Currat, K.M. Heeger, K.T. Lesko, A.D. Marino, E.B. Norman, C.E. Okada, A.W.P. Poon, S.S.E. Rosendahl, R.G. Stokstad Lawrence Berkeley National Laboratory M.G. Boulay, S.R. Elliott, J. Heise, A. Hime, R.G. Van de Water, J.M. Wouters Los Alamos National Laboratory T. Kutter Louisiana State University

  4. 1000 tonnes of D2O 12m diameter acrylic vessel 17m diameter PMT support structure with ~9500 PMTs 7000 tonnes of H2O Urylon liner and radon seal Norite rock The Sudbury Neutrino Observatory 2039m to surface 6800 ft level INCO’s Creighton Mine Sudbury, Ontario

  5. Charged Current • D+nep+p+e- • Electron energy closely corresponds to neutrino energy. FCC=Fe • Neutral Current • D+nxp+n+nx • Equally sensitive to all active neutrino flavors. • Threshold 2.2MeV. FNC=Fe + Fmt • Elastic Scattering • e-+nxe-+nx • Good directional sensitivity. • Enhanced ne sensitivity. FES=Fe + 0.154Fmt Sensitivity to Neutrino Flavour:Signals in SNO

  6. Neutron Detection: The 3 Phases of SNO. • Phase 1: Pure D2O. • Nov 1999 – May 2001 : 306 days. • Neutrons Capture on D • Detect 6.25MeV g-ray. • Phase 2: D2O+NaCl • Jul 2001-Sep 2003 : 391 days. • Neutrons Capture on 35Cl • Detect multiple g-rays. SE=8.6MeV • Phase 3: 3He Proportional Counters (NCD) • Nov 2004-Dec 2006 • Neutrons capture on 3He • Captures are detected in the counters.

  7. Events/Day E/MeV Why add salt? Detection Eff /% • Increase in Capture Cross Section. • 0.5mb→44b • Increase in visible Cerenkov energy. • More neutrons above threshold. • Detection efficiency: 14.4% → 40.7% • Multiple g-rays in the final state. • Events are more isotropic. • Can statistically separate neutrons from electrons. r/cm

  8. Measuring Isotropy • Use the angle between PMT hits from the fit event vertex. • Decompose distribution in spherical harmonics. • Use b14 = b1 + 4b4 • Note that b14 depends on energy. • Contribution of b14 uncertainty is relatively large. • 4% of CC,NC flux.

  9. Low energy isotropy fit. b14 Rn spike. Data:MC comparison Teff/MeV Radioactive Backgrounds • Three low energy decay of concern. • 208Tl (Th chain) • 214Bi (U chain / Rn) • 24Na (Na activation) • Two sources of background. • Neutrons (Eg>2.2MeV) • Cherenkov Tail. Teff>5.5MeV • New Calibration using Rn spikes. • Two monitoring techniques • Ex-situ: Radio Assays. • In-situ: Cherenkov light. • Fit to isotropy distribution at low energy.

  10. Extraction of Neutrino Signals. CC ES NC • Carry out a maximum Likelihood fit of the data to signal PDFs. • 4 Dimensional fit. • Energy. • Radius. • Direction. • Isotropy (salt only). • In salt isotropy allows us to drop CC and ES energy PDFs. • Model Independent Flux Extraction. • Extract the Spectrum. E/MeV (r/600cm)3 cos(q) Isotropy

  11. Fit Results Isotropy • Full Salt Data Set: 391 Days. • Fit for CC,NC,ES and External Neutrons. • nucl-ex/0502021 Radius Direction

  12. Flavour content of solar flux. Neutrino Fluxes • Fit Using: • Teff>5.5MeV • rfit<550cm • Dominant systematics • b14 Mean Value • Energy Scale • Radial Bias • Neutron Capture (NC) • Angular Resolution (ES)

  13. CC Spectrum and LMA CC events ES events Electron Energy Spectra • Fit to data was done without CC/ES energy constraints. • Spectra Extracted from Fit. • Beware Correlations. • Systematic CCiCCj • Statistical CCiNCCCj

  14. ANC floating ACC Teff/MeV ACC ANC 0 Teff/MeV Day-Night Asymmetry • Can carry out many analyses. • ANC floating • ANC 0 • Include/Remove CC,ES spectral constraints. • Statistics Dominated Results. • ACC = -0.037±0.071 • ANC 0 • CC,ES Spectrum Unconstrained • Extract asymmetry spectrum. • Best fit LMA shown. • Combine with D2O result. • Ae,combined= 0.037±0.040 • ANC 0 • CC/ES Spectrum Constrained

  15. All Solar Data Solar + KamLAND Interpretation of Results. • With SNO results • Large mixing angle regions are selected. • Maximal mixing is rejected. • Add other solar data. • LMA region is selected. • Add KamLAND data.

  16. Phase 3 : 3He Counters. • Timeline to phase 3 • Salt Removal. • Sept 2003. • PMT Electronics Upgrade. • Oct/Nov 2003. • Counter Deployment. • Nov2003-May2004. • Commissioning. • May – Nov 2004. • Phase 3 Production Data. Taking Commences. • Nov 2004. 40 Strings on 1 m grid. Total Active length 398m.

  17. 3He Counters. Baseline Analysis: Background Free Region. • n+3He p+T • Measure Current vs Time in the proportional counters. • Expect capture efficiency: • ~25% on 3He • ~20% on D • Unique identification of neutrons. • Substantially reduce CCNC correlation. • Reduce uncertainty in CC/NC • Reduce uncertainty in q12 Pulse Width / ms E/KeV

  18. Current /Arb Units A neutron Time/ns Current /Arb Units A fork event Time/ns Instrumental Backgrounds. • To carry out neutron analysis, we need to remove instrumental backgrounds. • We are developing a suite of cuts. Time/ns A fork cut

  19. PMT Data in Phase 3. • Presence of proportional counters blocks lights. • Adds effective attenuation. • Fewer hits per MeV • Breaks Spherical Symmetry • New Background Sources. • U/Th on the counters. Compensate by: Lower Trigger Threshold. Lower Channel Thresholds. Increased PMT High Voltage. More Complex Signal Extraction. More Complicated insitu Background Analysis New variables: Distance to Nearest Counter.

  20. En/MeV Enhanced Spectral Analysis SNO CC Effective Threshold. • The current LMA paradigm suggests that the ne survival probability increases sharply between 1-5MeV • Our current threshold is Te>5.5MeV • Q value for CC reaction is 1.4MeV • Lower our threshold to look for the turn up. • Positively identify LMA. • Look for new physics. • Non standard interactions. Miranda, Tortola, Valle: hep-ph/0406280

  21. To lower the threshold and improve spectral determination we must fight backgrounds. Cherenkov Tail Events 208Tl,214Bi,24Na D2O and H2O tails. Neutrons Background Neutrons NC events. Reduce Cherenkov tail: Reduce total background. Select data with lower background levels. Lower background levels in the water. Reduce background in the signal box Reduce energy resolution. Reduce energy systematics. Improve reconstruction. Enhanced Spectral Analysis • Reduce covariance between neutrons and electrons. • Isotropy. • 3He Counters. • Multi-Phase fits. • Fit the background and signal simultaneously.

  22. Improved Energy Estimation Model Local Variations. Reduce Energy Uncertainties. 16N Use “Late” Light. Increase Hit Statistics Reduce Energy Resolution. (R/RAV)3

  23. Other Physics Topics • Solar Neutrino Topics • hep Neutrinos. • Periodicity • Muons • Atmospheric Neutrino Oscillations via Through-Going Muons. • Measure flux normalzation above the Horizion. • Muon Spallation. • Exotic Physics • Proton Decay • Neutron – AntiNeutron Oscillations. • Supernovae

  24. Conclusions • SNO results show that neutrinos change flavour. • Along with other data the LMA neutrino oscillation solution is selected. • Phase 3 is underway. • Further reductions in the size of the LMA region are expected. • SNO plans an enhanced spectral analysis to look for positive signatures of LMA.

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