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Evidence of Neutrino Oscillation from SNO

Evidence of Neutrino Oscillation from SNO. Chun Shing Jason Pun Department of Physics The University of Hong Kong Presented at the HKU Neutrino Workshop 28 November, 2003. Outline. The Solar Neutrino Problem (Brief) Descriptions of SNO Results from SNO Future (and present) plans for SNO

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Evidence of Neutrino Oscillation from SNO

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  1. Evidence of Neutrino Oscillation from SNO Chun Shing Jason Pun Department of Physics The University of Hong Kong Presented at the HKU Neutrino Workshop 28 November, 2003

  2. Outline • The Solar Neutrino Problem • (Brief) Descriptions of SNO • Results from SNO • Future (and present) plans for SNO * Acknowledgement: This presentation borrows heavily from SNO member, Dr Alan W.P. Poon (LBL).

  3. 1.The Solar Neutrino Problem • Solar neutrinos provide a unique opportunity to study physics beyond the standard model. • Huge flux: • Long baseline: 1 AU = 1.5x108 km • Relatively low neutrino energy (~ MeV)

  4. 1. pp chain and Standard Solar Model p+p2H+e++ne p+e+p2H+ne [pp n ] [pep n ] p+2H 3He+g 85% 15% 3He+p4He+ e++ne [hep n ] 3He+4He7Be+g Overall:4p + 2e  4He +2ne+ 26.7MeV 0.02% 7Be+ e-7Li+ne 7Li+p4He+4He 7Be+p8B+g 8B8Be*+e++ne 8Be*4He+4He [7Be n ] [8B n ]

  5. Combining with detailed model of solar evolution, we get the Standard Solar Model (SSM) (CC) (cm-2 s-1) SNO(NC)

  6. 1.Solar Neutrino Problem Increasing detection energy threshold • The discrepancy suggests either • Solar models are incomplete and/or incorrect • Neutrinos undergo flavor-changing transformation along the way from the Sun to Earth

  7. 1. Astrophysical Solution to the Problem • Reduce the solar core temperature Tc to lower the predicted flux, e.g. Fn(8B) T25 • BUT: Poor agreement with other parameters • SSM accurately describes many observations Speed of sound in solar interior

  8. Neutrino Oscillation

  9. Combination of baseline/neutrino-energy (L/E) probes different regions in the (Dm2,tan2q) parameter space. • Mikheyev-Smirnov-Wolfenstein (MSW) effect: resonance enhancement of the oscillation amplitude in dense matter (e.g. solar interior) (Murayama 2003)

  10. 2. The Sudbury Neutrino Observatory (SNO) 1000 tons D2O • 2km underground in Sudbury, Canada • 9456 20-cm PMTs in a 12m diameter vessel (56% coverage)

  11. p n +  + + - e CC d p e e e- d p p n +  + + n NC d p n x x x x d p n ES - - +  + n e n e x x x x e- e- 2. Neutrino reactions at SNO • Charged Current: • Measurement of ne spectrum • Weak directionality: 1-0.340cosq • Neutral Current: • Measure total solar 8B n flux • flux s(ne)=s(nm)=s(nt) • Elastic Scattering: • Low statistics, strong directionality • flux s(ne) ≈ 6s(nm) ≈ 6s(nt)

  12. 2. Neutrino Oscillation at SNO • Ifno oscillation, solar neutrinos would be pure ne. • Measure the ratio, If ne transform into other flavors, then • Alternatively, can also measure the ratio and detect transformation if

  13. 3. Results from SNO • Electron neutrino event recovered from the Cherenkov radiation of the e-. 42o cone angle e-

  14. 3. NC measurement at SNO • Measurement of the NC is the most important for SNO • Key: Detect high energy neutrons • Three phases of measurements with different techniques and systematics • Phase I: Pure D2O (Nov 99 – May 01) • Phase II: Pure D2O + NaCl (Jul 01 – Sep 03) • Phase III: D2O + 3He Proportional Counters (Nov 03 – ?)

  15. 3. Phase I (Pure D2O) • CC, ES, some NCs • n + 2H →3H + g (6.25 MeV), s = 0.5 mb • Low neutron capture and detection efficiencies (en ~ 14% above threshold)

  16. 3. Phase I,PRL 87 (2001) 071301 • Measured fCC(ne) and compare with accurate ES results from Super-K [PRL 86 (2001) 5651] SK ES (1s) 1.6 s 3.3 s Excludespure nensterileat 3.1 s

  17. 3. Phase I,PRL 89 (2002) 011301, 02 • All pure D2O data used • Direct measurement of total 8B flux fNC(nX) 1.6 s

  18. 3. Main Results (Phase I) • Excludefmn = 0 at 5.3s • SSM prediction verified (flux in units of 10-6 cm-2 s-1): Bahcall, Pinsonneault & Basu (2001）ApJ, 555, 990

  19. 3. Phase II (Pure D2O + NaCl) • 2 tonnes of NaCl added • CC, ES, enhanced NCs • n + 35Cl→36Cl* + Sg’s(8.6 MeV), s = 44 b • High neutron capture efficiency with higher energy release (en ~ 40% above threshold)

  20. 3. Phase II,nucl-ex/0309004 • Spectral distributions of the ES and CC events are not constrained to the standard 8B spectral shape. • Measured total 8B flux (in units of 10-6 cm-2 s-1): Recall

  21. All Solar n experiments + KamLAND SNO Only 3. Constraints on Dm2 and tan2q Best fit: Dm2 = 4.7x10-5, tan2q = 0.43 Best fit: Dm2 = 6.5x10-5, tan2q = 0.40

  22. 4. Phase III (Pure D2O + 3He) • Arrays of 3He proportional counters (Neutral Current Detectors, NCD) inserted • n + 3He→p + 3H + 760keV (en ~ 37%) • Motives: • CC, NC measured in separate data streams • Different systematic uncertainties • Search for direct evidence of MSW effect, from CC spectral shape distortion.

  23. 4. Phase III (Pure D2O + 3He) • Nov 2003 – ? • 40 strings on 1-m grid • 440m total active length. • Installed by a small remote control submarine

  24. The SNO Collaboration S.D. Biller, M.G. Bowler, B.T. Cleveland, G. Doucas, J.A. Dunmore, H. Fergani, K. Frame, N.A. Jelley, 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, M. Dunford, W.J. Heintzelman, C.C.M. Kyba, N. McCauley, V.L. Rusu, R. Van Berg University of Pennsylvania S.N. Ahmed, M. Chen, F.A. Duncan, E.D. Earle, B.G. Fulsom, H.C. Evans, G.T. Ewan, K. Graham, A.L. Hallin, W.B. Handler, P.J. Harvey, M.S. Kos, A.V. Krumins, J.R. Leslie, R. MacLellan, H.B. Mak, J. Maneira, A.B. McDonald, B.A. Moffat, A.J. Noble, C.V. Ouellet, B.C. Robertson, P. Skensved, M. Thomas, Y.Takeuchi Queen’s University D.L. Wark Rutherford Laboratory and University of Sussex R.L. Helmer TRIUMF A.E. Anthony, J.C. Hall, J.R. Klein 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, R.G.H. Robertson, M.W.E. Smith, L.C. Stonehill, B.L. Wall, J.F. Wilkerson University of Washington T. Kutter, C.W. Nally, S.M. Oser, C.E. Waltham 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, R.J. Hemingway, I. Levine, C. Mifflin, E. Rollin, O. Simard, D. Sinclair, N. Starinsky, G. Tesic, D. Waller Carleton University P. Jagam, H. Labranche, J. Law, I.T. Lawson, B.G. Nickel, R.W. Ollerhead, J.J. Simpson University of Guelph J. Farine, F. Fleurot, E.D. Hallman, S. Luoma, M.H. Schwendener, R. Tafirout, C.J. Virtue Laurentian University Y.D. Chan, X. Chen, 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, T.J. Bowles, S.J. Brice, M.R. Dragowsky, S.R. Elliott, M.M. Fowler, A.S. Hamer, J. Heise, A. Hime, G.G. Miller, R.G. Van de Water, J.B. Wilhelmy, J.M. Wouters Los Alamos National Laboratory

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