RESULTS FROM SNO. Art McDonald For the SNO collaboration Nobel Symposium Stockholm, August 18, 2004

Size: px

Start display at page:

Download "RESULTS FROM SNO. Art McDonald For the SNO collaboration Nobel Symposium Stockholm, August 18, 2004"

Branden Atkins
6 years ago
Views:

1 RESULTS FROM SNO Art McDonald For the SNO collaboration Nobel Symposium Stockholm, August 18, 4

2 SOLAR FUSION CHAIN SNO is designed to search for direct evidence of flavor transformation for neutrinos from 8 B decay in the Sun. Both electron neutrinos and all active neutrinos are measured to exhibit the appearance of other neutrino types.

Solar Neutrino Problem Solar Fluxes: Bahcall et al Experiment vs Solar Models 197-1 Smaller

3 Solar Neutrino Problem Solar Fluxes: Bahcall et al Experiment vs Solar Models Smaller than expected flux of electron neutrinos: From Neutrino Flavor Change or Solar Model Effects?

4 i li l U ν ν = If neutrinos have mass: Using the oscillation framework for neutrino flavor change: For three neutrinos: ij ij ij ij i i i τ τ τ µ µ µ e e e li s and where c e e c s s c iδ e c s s c c s s c U U U U U U U U U U θ θ δ α α sin, cos / / = = = = + ) E L m. ( θ ) ν P(ν e µ 17 sin = sin Solar,Reactor Atmos., Accel. For two neutrino oscillation in a vacuum: (valid approximation in many cases) CP Violating Phase Reactor, Accel Majorana Phases Range defined for m 1, m 3 Maki-Nakagawa-Sakata-Pontecorvo (MNSP) matrix (Double β decay only)

5 Matter Effects the MSW effect i d dt ν e ν x = H ν e ν x m m cosθ + G FNe H = 4E 4E m m sinθ 4E 4E (Mikheyev, Smirnov, Wolfenstein) sinθ cosθ The extra term arises because ν e have an extra interaction via W exchange with electrons in the Sun or Earth. In the oscillation formula: sin θ m ω = = ( ω G sin θ cosθ ) + sin F N e E / m θ

6 Solar Model Independent Measurements: SuperKamiokande, SNO (Using 8 B Solar Neutrinos) SuperKamiokande Measurements MSW Effects - Distortion of the spectrum - Regeneration in the Earth (Day/Night Effects) Other Time Dependent Effects - Seasonal effects (Earth-Sun Distance, Neutrino Magnetic Moments..) - Long Term: Solar cycle (Neutrino Magnetic Moments ) None of the above effects are seen with clear signals of oscillations However: Sudbury Neutrino Observatory Charged Current to Neutral Current comparisons - Electron Neutrino flux compared to Total Active Neutrino flux

7 Unique Signatures in SNO (D O) Charged-Current (CC) ν e +d e - +p+p E thresh = 1.4 MeV ν e only Neutral-Current (NC) ν x +d ν x +n+p E thresh =. MeV 3 ways to detect neutrons Equally sensitive to ν e ν µ ν τ Elastic Scattering (ES) ν x +e - ν x +e - ν x, but enhanced for ν e

8 Solar Neutrino Physics From SNO Flavor change + active neutrino appearance June 1 (with SK) Φ CC Φ ES = ν e ν e +.15 (ν µ + ν τ ) 3.3 σ April Sept. 3 (With salt) Φ CC Φ NC = ν e ν e + ν µ + ν τ 5.3 σ > 7 σ Total 8 B Solar Neutrino Flux June 1 Φ x = Φ CC + (Φ ES - Φ CC ) x (1/.15) April Sept. 3 Φ x = Φ nc ~1%

9 Sudbury Neutrino Observatory 1 tonnes D O Support Structure for 95 PMTs, 6% coverage 1 m Diameter Acrylic Vessel 17 tonnes Inner Shielding H O 53 tonnes Outer Shield H O Urylon Liner and Radon Seal

10 One million pieces transported and assembled under ultra-clean conditions. More than 6, showers and counting

11 3 neutron (NC) detection Phase I (D O) Nov May 1 n captures on H(n, γ) 3 H Effc. ~14.4% NC and CC separation by energy, radial, and directional distributions H+n 6.5 MeV methods Phase II (salt) July 1 - Sep. 3 t NaCl. n captures on 35 Cl(n, γ) 36 Cl Effc. ~4% NC and CC separation by event isotropy 35 Cl+n 8.6 MeV Phase III ( 3 He) Summer 4-Dec. 6 4 proportional counters 3 He(n, p) 3 H Effc. ~ 3% capture Measure NC rate with entirely different detection system. 5 cm n 3 H 3 He p 3 H 36 Cl n + 3 He p + 3 H

12 Observables PMT Measurements -position -time -charge 14 x PMT charge Reconstructed event -vertex -direction -energy -isotropy

13 6.13 MeV SNO Energy Calibrations 19.8 MeV Energy calibrated to ~1.5 % 5 Cf neutrons β s from 8 Li γ s from 16 N and t(p,γ) 4 He

14 Signals in SNO (Monte Carlo, Renormalized) Pure D O X.45 X 1/3 First Analysis: High Threshold, CC, ES only Jun 1 PRL 87, 7131 April : Further Analysis NC/CC, Day/Night PRL 89 () 1131, 113 ~ 9 NHIT/MEV

15 Measuring U/Th Radioactivity Concern:.4,.5 Mev gammas from U, Th decay chains could photodisintegrate deuterium, producing a neutron like the NC ν reaction. Response: Control U, Th, Rn and measure carefully at ~ 1-15 level Good agreement between techniques Isotropy of Low Energy Cerenkov Events in D O Radiochemistry Ion exchange ( 4 Ra, 6 Ra) Membrane degassing Count daughter product decays Total < 5 % of SSM NC Pure D O Salt Added

16 SNO NEUTRINO DATA: 36 Days OF Pure D O Events per 5 kev (c) CC Neutrino Energy CC: ELECTRON NEUTRINOS 1 NC + bkgd Bkgd neutrons ES (MeV) T eff Events per.5 wide bin Direction From the Sun (a) 6 4 CC ES NC + bkgd neutrons Bkgd cos θ sun Very Little Radioactive Background NC: ALL NEUTRINOS ES: POINTS AWAY FROM SUN Fix the CC shape to undistorted 8 B flux and see if the data Fits the NO NEUTRINO FLAVOR CHANGE Hypothesis.

17 Hypothesis test for NO Flavor Change Theory: Φ Standard Solar Model = Agreement with total flux measured by NC A comparison of the CC and NC fluxes implies that No Neutrino Flavor Change is disallowed by 5.3 Standard Deviations.

18 Physics Implication: Flavor Content Φ µτ is 5.3 σ from zero s -1 ) 6 cm - (1 φ µτ SNO φ ES SNO φ CC SNO φ NC SSM φ NC φ e 6 (1 - cm -1 s ) Clear evidence of flavor change

19 Solar Neutrino Flux Day/Night Asymmetries SNO Separate Spectra For Day and Night A x = (Φ NIGHT Φ DAY ) (Φ NIGHT +Φ DAY ) Day-Night Flux Asymmetry Signal Extraction in Φ CC, Φ NC, Φ ES Signal Extraction in Φ e, Φ total +A total = A SNO CC = 14. ± A SNO e = 7. ± A SNO NC = -.4 ± A SK e = 5.3 ± No significant day/night asymmetry observed

20 Physics Interpretation: Neutrino Oscillations log( m /ev ) -4-5 Combining SNO with All Experimental and Solar Model information (b) LMA Best Fit: Matter Effects (MSW): Large Mixing Angle % CL 95% CL 99% CL 99.73% CL LOW log(tan θ) Mass Heirarchy: log (tan θ 1 )< implies m > m 1 Maximal mixing (θ 1 = 45 o ) ruled out at 3 σ Θ 1 ~ 3 o

21 SNO Restrictions on θ 1 : For LMA and 8 B above 5 MeV: Φ Φ CC NC =.34±.5 sin θ1 Φ Total Active Measured = Improved accuracy improves θ 1 SNO Restrictions on sterile neutrinos: Compare Standard Solar Model calculation of 8 B flux with measured value of total flux of active neutrinos: Φ SSM = (Bahcall, Pinsonneault, ) For oscillations to ν e, ν x, where: ν x = cos η ν µτ + sin η ν sterile Then sin η <.35 (1 σ)

22 Overlapping allowed region of oscillation parameters from Kamland with Reactor AntiNeutrinos, Dec. Combine Kamland with SNO LMA for further restrictions on sterile neutrinos Additional disappearance evidence for anti - ν e oscillation.

23 SNO Phase : NaCl for Neutron Detection Energy Higher capture cross section Higher energy release Many gammas 6. MeV σ =.5 b H+n 3 H NC CC σ = 44 b 35 Cl+n 8.6 MeV 36 Cl

24 SNO Phase : NaCl for Neutron Detection Isotropy Parameter based on distribution of PMT hits Higher capture cross section Higher energy release Many gammas 6. MeV σ =.5 b H+n 3 H NC CC σ = 44 b 35 Cl+n 8.6 MeV 36 Cl

25 Signal Extraction for Salt Blind Analysis performed by adding in an unknown number of neutrons generated by muons Data from July 6, 1 to Oct. 1, Isotropy 54. live days 355 candidate events: CC NC ES Phys.Rev.Lett. 9 (4) 18131

26 Signal Extraction for Salt Blind Analysis performed by adding in an unknown number of neutrons generated by muons Data from July 6, 1 to Oct. 1, Angle to Sun 54. live days 355 candidate events: CC NC ES Phys.Rev.Lett. 9 (4) 18131

27 Signal Extraction for Salt Blind Analysis performed by adding in an unknown number of neutrons generated by muons Data from July 6, 1 to Oct. 1, 54. live days 355 candidate events: CC NC ES Phys.Rev.Lett. 9 (4) 18131

28 Signal Extraction for Salt Blind Analysis performed by adding in an unknown number of neutrons generated by muons Data from July 6, 1 to Oct. 1, 54. live days 355 candidate events: Kinetic Energy CC NC ES Phys.Rev.Lett. 9 (4) 18131

29 Salt Phase: Blind Box Open Aug. 13, 3 Φ Φ Φ II unc. CC II unc. ES II unc. NC 8 B shape unconstrained 8 B shape constrained II cons. +.9 = 1.59 ( stat.) ( syst.) Φ = 1.7 ±.7( stat.) ( syst.) = ( stat.) ±.1( syst.) = 5.1 ±.7( stat.) ±.38( syst.) Φ Φ CC II cons. ES II cons. NC = ( stat.) = 4.9 ±.4( stat.).1 ( syst.) ( syst.) Φ SSM = Independent measurement of total 8 B flux = SSM Improves restriction on sterile neutrinos Φ CC / Φ NC =.36 ±.6( stat) ±.4( syst) sin θ1 (Improved accuracy) Further clear evidence for Flavor Change (> 7 σ) through independent measurements of Φ(ν e ) and Φ(ν Total Active ) Φ CC 4 4 / Φ NC cos θ 13 sin θ1 + sin θ13 (For LMA, 8 B) Solar neutrinos provide restrictions on θ 13 for small m 3.

30 After SNO Salt Data: Closing in on m 1, θ 1 --9% --95% --99% % Maximal Mixing disallowed at 5.4 σ : θ 1 = o LMA only at > % CL

SNO Phase III (NCD Phase) 3 He Proportional Counters ( NC Detectors ) 4 Strings on 1-m grid 44 m total active length Detection Principle H + ν x p + n + ν x -. MeV (NC) ν x PMT 3 He + n p + 3 H +.

31 SNO Phase III (NCD Phase) 3 He Proportional Counters ( NC Detectors ) 4 Strings on 1-m grid 44 m total active length Detection Principle H + ν x p + n + ν x -. MeV (NC) ν x PMT 3 He + n p + 3 H +.76 MeV Physics Motivation Event-by-event separation. Measure NC and CC in separate data streams. Different systematic uncertainties than neutron capture on NaCl. NCD array removes neutrons from CC, calibrates remainder. CC spectral shape. NCD n

32 Deployment completed, full detector in operation. Calibration, final test data in progress.

33 Uncertainties for NC Flux Fully Independent Measurement In NCD Phase, Improved Accuracy D O unconstrained D O constrained Salt unconstrained NCD Phase NC,CC ~ CC,ES ~-. ES,NC ~ By 7 Removes Correlations

34 Solar Neutrinos SNO Physics Program Electron Neutrino Flux Total Neutrino Flux Electron Neutrino Energy Spectrum Distortion (Predicted ~1 %) Day/Night effects (Predicted ~ 4 %) Seasonal variations Atmospheric Neutrinos & Muons Downward going cosmic muon flux Upward going muons and angular dependence Supernova Watch (SNEWS) Electron Antineutrinos hep-ex/479 Nucleon decay ( Invisible Modes: N ννν) Phys.Rev.Lett. 9 (4) hep-ex/313

35 SNO Muon & Atmospheric Neutrino Analysis

36 Invisible Nucleon Decay in SNO Phys.Rev.Lett. 9 (4) hep-ex/313 Look for N-> invisible such as n -> 3 ν by searching for ~ 6 MeV gammas from the de-excitation of 16 O after neutron or proton decay. By comparison of the SNO data with and without salt, a limit of 3.9 x 1 9 years was obtained at 9% confidence level. This is about one order of magnitude lower than previous limits on invisible modes for protons and about 3 orders of magnitude better than previous limits for neutrons.

37 Summary of SNO results Direct observation of neutrino flavor change via appearance measurement. Dominant transformation is to active neutrinos. Strong confirmation of 8 B flux calculations by Standard Solar Model. With other solar measurements: Strong evidence for Matter Enhancement in Sun (MSW). Accurate measurement of θ 1 and m 1. With Kamland: Strong evidence of oscillation due to finite mass (MNSP), strong restrictions on sterile neutrinos.

38 The SNO Collaboration S. Gil, J. Heise, R.L. Helmer, R.J. Komar, T. Kutter, S. M. Oser, C.W. Nally, H.S. Ng, R. Schubank, Y. Tserkovnyak, T. Tsui, C.E. Waltham, J. Wendland University of British Columbia J. Boger, R. L Hahn, R. Lange J.K. Rowley, M. Yeh Brookhaven National Laboratory I. Blevis, A. Bellerive, X. Dai, F. Dalnoki-Veress, R. S. Dosanjh, W. Davidson, J. Farine, D.R. Grant, C. K. Hargrove, R. J. Hemingway, I. Levine, K. McFarlane, H. Mes, C. Mifflin, V.M. Novikov, M. O'Neill, E. Rollin, M. Shatkay, C. Shewchuk, O. Simard, D. Sinclair, N. Starinsky, G. Tesic, D. Waller Carleton University T. Andersen, K. Cameron, M.C. Chon, P. Jagam, J. Karn, H. Labranche, J. Law, I.T. Lawson,B. G. Nickel, R. W. Ollerhead, J. J. Simpson, N. Tagg, J.X. Wang University of Guelph B. Aharmim, J. Bigu, J.H.M. Cowan, J. Farine, F. Fleurot, N. Gagnon, E. D. Hallman, R. U. Haq, J. Hewett, J.G. Hykawy, G. Jonkmans, A. Kruger, S. Luoma, A. Roberge, E. Saettler, M.H. Schwendener, H. Seifert, R. Tafirout, C. J. Virtue Laurentian University Y. D. Chan, X. Chen, C. A. Currat, M.C.P. Isaac, K. M. Heeger, K. T. Lesko, A.D. Marino, E.B. Norman, C.E. Okada, A.W. P. Poon, S. S. E. Rosendahl, A. R. Smith, A. Schuelke, 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. Goldschmidt, A. Hime, J. Heise, K. Kirch, G. G. Miller, P. Thornewell, R. G. Van de Water, J. B. Wilhelmy, J. M. Wouters. Los Alamos National Laboratory R.G. Allen, G. Buhler, H.H. Chen* University of California J. D. Anglin, M. Bercovitch, W. F. Davidson, R. S. Storey* National Research Council of Canada J. C. Barton, S. D. Biller, R. A. Black, R. Boardman, M. G. Bowler, J. Cameron, B. T. Cleveland, G. Doucas, J. A. Dunmore, A. P. Ferraris, H. Fergani, K.Frame, H. Heron, C. Howard, N. A. Jelley, A. B. Knox, M. Lay, J. C. Loach, W. Locke, J. Lyon, N. McCaulay, S. Majerus, G. McGregor, M. Moorhead, M. Omori, S. J. M. Peeters, C. J. Sims, N. W. Tanner, R. Taplin, M. Thorman, P. T. Trent, D. H. Wan Chan Tseung, N. West, J. R. Wilson, K. Zuber Oxford University E. W. Beier, D. F. Cowen, J. Deng, M. Dunford, E. D. Frank, W. Frati, W. J. Heintzelman, P.T. Keener, C. C. M. Kyba, N. McCauley,D. S. McDonald, M.S.Neubauer, F. M. Newcomer,V. L. Rusu, R. Van Berg, P. Wittich. University of Pennsylvania M.M. Lowry, Princeton University S.N. Ahmed, E. Bonvin, M. G. Boulay, M. Chen, E. T. H. Clifford, Y. Dai, F. A. Duncan, E. D. Earle,H. C. Evans, G.T. Ewan, R. J. Ford, B. G. Fulsom, K. Graham, W. B. Handler, A. L. Hallin, A. S. Hamer*, P. J. Harvey, R. Heaton, J. D. Hepburn, C. Jillings, M. S. Kos, L. L. Kormos, R. Kouzes, C. B. Krauss, A. V. Krumins, H. W. Lee, J. R. Leslie, R. MacLellan, H. B. Mak, J. Maneira, A. B. McDonald, W. McLatchie, B. A. Moffat, A. J. Noble, C. Ouellet, T. J. Radcliffe, B.C. Robertson, P. Skensved, B. Sur. Y. Takeuchi, M. Thomson 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 Q. R. Ahmad, M. C. Browne, T.V. Bullard, T. H. Burritt, G. A. Cox, P. J. Doe, C. A. Duba, S. R. Elliott, R. Fardon, J. A. Formaggio, J.V. Germani, A. A. Hamian, R. Hazama, K. M. Heeger, M. A. Howe, S. McGee, R. Meijer Drees, K. K. S. Miknaitis, N. S. Oblath, J. L. Orrell, K. Rielage, R. G. H. Robertson, K. Schaffer, M. W. E. Smith, T. D. Steiger, L. C. Stonehill, B. L. Wall, J. F. Wilkerson. University of Washington G. Milton, B. Sur, AECL, Chalk River *deceased

39 SNOLAB We have $5 Million to expand and create an International Lab at the same depth as SNO. The lowest muon flux available for future experiments

40 SNO

41 Letters of Interest for SNOLAB May 4 Solar Neutrinos: Liquid Scintillator in SNO: SNO+ (also Double Beta Decay, Reactor Neutrinos, Geoneutrinos, Supernovae) Liquid Ne: CLEAN (also Dark Matter) Liquid Helium (also Dark Matter) Dark Matter: Silicon Bolometers: CDMS Liquid Xe: ZEPLIN, XENON Gaseous Xe: DRIFT Freon Super-saturated Gel: PICASSO Neutrinoless Double Beta Decay: Ge Crystals: Individual cryostats (MAJORANA) or Large Liquid Nitrogen bath Liquid Xe: EXO CdTe: COBRA

The Sudbury Neutrino Observatory

The Sudbury Neutrino Observatory First Results GordonMcGregor (University of Oxford) for the SNO Collaboration XXXVIIth Rencontres de Moriond March 12 th 2002 Nuclear Fusion pp 2 H + e + +ν e 2 H + p 3