html5-img
1 / 45

SNO II: Salt Strikes Back

SNO II: Salt Strikes Back. Update from the Sudbury Neutrino Observatory. Joseph A. Formaggio University of Washington NuFACT’03. Our understanding of neutrinos has changed in light of new evidence: Neutrinos no longer massless particles (though mass is very small)

yetty
Download Presentation

SNO II: Salt Strikes Back

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. SNO II:Salt Strikes Back Update from the Sudbury Neutrino Observatory Joseph A. Formaggio University of Washington NuFACT’03

  2. Our understanding of neutrinos has changed in light of new evidence: Neutrinos no longer massless particles (though mass is very small) Experimental evidence from three different phenomena: Solar Atmospheric Accelerator Reactor Data supports the interpretation that neutrinos oscillate. Beyond a Reasonable Doubt… Murayama

  3. Need to measure nx sloar flux, independently of ne or solar model EXPERIMENTAL RESULTS Chlorine flux = 34% SSM Gallium flux = 57% SSM Super-K flux = 47% SSM Solar Neutrino Experiments

  4. The SNO Experiment

  5. Light Element Fusion Reactions p + p 2H + e+ + e p + e- + p  2H + e 99.75% 0.25% 2H + p 3He +  ~10-5% 85% ~15% 3He + 3He 4He + 2p 3He + 4He 7Be +  3He + p 4He + e+ +e 15.07% 0.02% 7Be + e- 7Li +  +e 7Li + p   +  7Be + p 8B +  8B  8Be* + e+ + e Mapping the Sun with n’s • Neutrinos from the sun allow a direct window into the nuclear solar processes. • Each process has unique energy spectrum • Only electron neutrinos are produced • SNO sensitive to 8B neutrinos

  6. The SNO Collaboration G. Milton, B. Sur Atomic Energy of Canada Ltd., Chalk River Laboratories S. Gil, J. Heise, R.J. Komar, T. Kutter, C.W. Nally, H.S. Ng, Y.I. Tserkovnyak, C.E. Waltham University of British Columbia J. Boger, R.L Hahn, J.K. Rowley, M. Yeh Brookhaven National Laboratory R.C. Allen, G. Bühler,H.H.Chen* University of California, Irvine I. Blevis, F. Dalnoki-Veress, D.R. Grant, C.K. Hargrove, I. Levine, K. McFarlane, C. Mifflin, V.M. Novikov, M. O'Neill, M. Shatkay, D. Sinclair, N. Starinsky Carleton University T.C. Andersen, P. Jagam, J. Law, I.T. Lawson, R.W. Ollerhead, J.J. Simpson, N. Tagg, J.-X. Wang University of Guelph J. Bigu, J.H.M. Cowan, J. Farine, E.D. Hallman, R.U. Haq, J. Hewett, J.G. Hykawy, G. Jonkmans, S. Luoma, A. Roberge, E. Saettler, M.H. Schwendener, H. Seifert, R. Tafirout, C.J. Virtue Laurentian University Y.D. Chan, X. Chen, M.C.P. Isaac, K.T. Lesko, A.D. Marino, E.B. Norman, C.E. Okada, A.W.P. Poon, S.S.E Rosendahl, A. Schülke, A.R. Smith, R.G. Stokstad Lawrence Berkeley National Laboratory M.G. Boulay, T.J. Bowles, S.J. Brice, M.R. Dragowsky, M.M. Fowler, A.S. Hamer*, A. Hime, G.G. Miller, R.G. Van de Water, J.B. Wilhelmy, J.M. Wouters Los Alamos National Laboratory J.D. Anglin, M. Bercovitch, W.F. Davidson, R.S. Storey* National Research Council of Canada J.C. Barton, S. Biller, R.A. Black, R.J. Boardman, M.G. Bowler, J. Cameron, B.T. Cleveland, X. Dai, G. Doucas, J.A. Dunmore, H. Fergani, A.P. Ferrarris, K. Frame, N. Gagnon, H. Heron, N.A. Jelley, A.B. Knox, M. Lay, W. Locke, J. Lyon, S. Majerus, G. McGregor, M. Moorhead, M. Omori, C.J. Sims, N.W. Tanner, R.K. Taplin, M.Thorman, P.M. Thornewell, P.T. Trent, N. West, J.R. Wilson University of Oxford E.W. Beier, D.F. Cowen, M. Dunford, E.D. Frank, W. Frati, W.J. Heintzelman, P.T. Keener, J.R. Klein, C.C.M. Kyba, N. McCauley, D.S. McDonald, M.S. Neubauer, F.M. Newcomer, S.M. Oser, V.L Rusu, S. Spreitzer, R. Van Berg, P. Wittich University of Pennsylvania R. Kouzes Princeton University E. Bonvin, M. Chen, E.T.H. Clifford, F.A. Duncan, E.D. Earle, H.C. Evans, G.T. Ewan, R.J. Ford, K. Graham, A.L. Hallin, W.B. Handler, P.J. Harvey, J.D. Hepburn, C. Jillings, H.W. Lee, J.R. Leslie, H.B. Mak, J. Maneira, A.B. McDonald, B.A. Moffat, T.J. Radcliffe, B.C. Robertson, P. Skensved Queen’s University D.L. Wark Rutherford Appleton Laboratory, University of Sussex R.L. Helmer, A.J. Noble TRIUMF Q.R. Ahmad, M.C. Browne, T.V. Bullard, G.A. Cox, P.J. Doe, C.A. Duba, S.R. Elliott, J.A. Formaggio, J.V. Germani, A.A. Hamian, R. Hazama, K.M. Heeger, K. Kazkaz, J. Manor, R. Meijer Drees, J.L. Orrell, R.G.H. Robertson, K.K. Schaffer, M.W.E. Smith, T.D. Steiger, L.C. Stonehill, J.F. Wilkerson University of Washington

  7. Somewhere in the Depths of Canada...

  8. Sudbury Neutrino Observatory 2092 m to Surface (6010 m w.e.) PMT Support Structure, 17.8 m 9456 20 cm PMTs ~55% coverage within 7 m Acrylic Vessel, 12 m diameter 1000 Tonnes D2O 1700 Tonnes H2O, Inner Shield 5300 Tonnes H2O, Outer Shield Urylon Liner and Radon Seal

  9. Unique Signatures Charged-Current (CC) e+d  e-+p+p Ethresh = 1.4 MeV e only Elastic Scattering (ES) x+e-  x+e- x, but enhanced for e Neutral-Current (NC) x+d  x+n+p Ethresh = 2.2 MeV x

  10. Results from Pure D2O • Measurement of 8B flux from the sun. • Final flux numbers: +1.01 - 0.81 8BSSM*= 5.05 +0.44 +0.46 - 0.43 -0.43 NCSNO*= 5.09 * in units of 106 cm-2 s-1

  11. SNO Phase II - Salt D2O Salt Enhanced NC sensitivity n~55% above threshold n+35Cl 36Cl+ ∑ Systematic check of energy scale E ∑= 8.6 MeV NC and CC separation by event isotropy NC sensitivity n~14.2% above threshold n+2H 3H+  Energy near threshold E = 6.25 MeV NC and CC separation by energy, radial, and directional distributions

  12. "Blinded" Data Advantages of Salt • Neutrons capturing on 35Cl provide much higher neutron energy above threshold. • Gamma cascade changes the angular profile. • Higher capture efficiency g n 36Cl* 36Cl 35Cl Same Measurement, Different Systematics

  13. Steps to a Signal Calibrations • Optics • Energy • Neutron Capture Backgrounds • Internal photo-disintegration • PMT - • External neutrons and other sources Signal Extraction • Charged current (CC) • Neutral Current (NC) • Elastic Scattering (ES)

  14. Calibration Pulsed Laser 16N 252Cf 8Li AmBe U & Th Sources Radon Spike Simulates... 337-620 nm optics 6.13 MeV g neutrons <13 MeV b decay 4.4 MeV (g ,n) source 214Bi & 208Tl (b,g) Rn backgrounds Sources of Calibration • Use detailed Monte Carlo to simulate events • Check simulation with large number of calibrations:

  15. Optical Calibration • The PMT angular response and attenuation lengths of the media are measured directly using laser+diffuser (“laserball”). • Attenuation for D2O and H2O, as well as PMT angular response, also measured in-situ using radial scans of the laserball. • Exhibit a change as a function of time after salt was added to the detector.

  16. Energy response of the detector determined from 16N decay. Mono-energetic g at 6.13 MeV, accompanied by tagged b decay. Provides check on the optical properties of the detector. Radial, temporal, and rate dependencies well modeled by Monte Carlo. 16N Calibration Source

  17. 252Cf • 8Li 16N Energy Response • In addition to 16N, additional calibration sources are employed to understand energy response of the detector. • Muon followers • 252Cf • 8Li • 24Na • Systematics dominated by source uncertainties, optical models, and radial/asymmetry distributions Energy Scale = +1.1%* Energy Resolution = +3.5%* *Preliminary

  18. Neutron Response • Use neutron calibration sources (252Cf and AmBe) to determine capture profile for neutrons. • 252Cf decays by a emission or spontaneous fission. • Observe resulting g cascade from neutron capture on 35Cl. • Monte Carlo agrees well with observed distributions. Neutrons/fission = 3.7676 +0.0047

  19. Neutron Efficiency • Capture efficiency increase by 4-fold in comparison to pure D2O phase. • Systematics include: • source position • energy response • source strength • modeling • Less than 3% total systematic uncertainty on capture. Salt Preliminary

  20. Backgrounds Calibrations • Optics • Energy • Neutron Capture Backgrounds • Internal photo-disintegration • PMT - • External backgrounds and other sources Signal Extraction • Charged current (CC) • Neutral Current (NC) • Elastic Scattering (ES)

  21. Uranium Thorium 3.27 MeV b 2.445 MeV g 2.615 MeVg An Ultraclean Environment • Highly sensitive to any g above neutral current (2.2 MeV) threshold. • Sensitive to 238U and 232Th decay chains “I will show you fear in a handful of dust.” -- T.S. Eliot

  22. Other Backgrounds Fission from possible U and Cf contamination Atmospheric neutrinos 24Na from the vessel 13C(a,n) 16O from acrylic a activation from radon embedded on the surface of the acrylic vessel. Measured from neutron radial profile and internal e+e- high-energy gamma conversion from 16O. Salt provides unique window of sensitivity to external neutrons. Uranium and Thorium Two methods: In-situ: Low Energy Data Separate 208Tl and 214Bi based on event isotropy Ex-situ: Ion exchange (224Ra, 226Ra) Membrane degassing Count daughter product decays Preliminary salt measurements yield background levels at par with what was measured in D2O U / Th and Other Backgrounds

  23. Steps to a Signal Calibrations • Optics • Energy • Neutron Capture Backgrounds • Internal photo-disintegration • PMT - • External Neutrons and other backgrounds Signal Extraction • Charged current (CC) • Neutral Current (NC) • Elastic Scattering (ES)

  24. NC E higher Less Rad. Sep. Energy R3 qij cosqsun Unconstrained Variables: E, R3, cosqsun, qij 8B Shape Constrained Isotropy Separation Directionality Unchanged Changes in Signal Extraction • Based on data taken from May 27, 2001 to October 10, 2002. • Total 254 live days of neutrino data. • Previous analysis used energy, radial, and solar angle distribution to separate events. • Introduction of salt moves neutron energy higher (but disrupts radial separation). • New statistical separation using event isotropy, allowing both energy dependent and independent analyses.

  25. Variables CC Stat. Error NC Stat. Error ES Stat. Error E,R,qsun 3.4% 8.6% 10% E,R,qsun 4.2% 6.3% 10% E,R,qsun,Iso 3.3% 4.6% 10% R,qsun,Iso 3.8% 5.3% 10% Fit Result Uncertainties (Monte-Carlo) D2O results Simulated Salt Phase Results Published D2O energy-unconstrained statistical error was 24% Simulations assume 1 yr of data with central values and cuts from D2O phase results

  26. What’s Inside Pandora’s Box?

  27. Projected SNO Assuming D2O NC Result De Holanda, Smirnov hep-ph/0212270 Day – Night Contours (%) Probability Contours

  28. Coming Soon...SNO III:Return of the Neutron

  29. x Detection Principle 2H + x p + n + x -2.22 MeV (NC) 3He + n p + 3H n SNO Phase IIIThe Neutral Current Detectors Array of 3He counters 40 Strings on 1-m grid 398 m total active length PMT NCD Physics Motivation Event-by-event separation. Measure NC and CC in separate data streams. Different systematic uncertainties than neutron capture on NaCl. NCD array as a neutron absorber.

  30. Counters • Ultraclean nickel counters of varying length, connected as “string”. • Mixture of 3He (85%) and CF4 (15%). • Anchored to the bottom of the acrylic vessel. • Radioassayed and polished to reduce U and Th backgrounds.

  31. A remote controlled submarine will be used to deploy the NCDs in the acrylic vessel. The bottom end of the NCD string will be pulled to the floor of the acrylic vessel directly below the neck with a pulley. The ROV will then move the bottom end of the string along the floor of the acrylic vessel to its anchor point and anchor it. The Remotely Operated Vehicle

  32. Salt Phase: More precise measurements of CC/NC ratio, due to increased sensitivity to neutrons. Ability to extract solar flux with and without assumptions regarding the energy spectrum. Final systematics and backgrounds currently being evaluated. NCD Phase: Event-by-event separation of charged current and neutral current events. Model-independent extraction of charged current and neutral current flux. Begin deployment of counters in October. Future Solar Physics

  33. ROV Training

  34. Use semi energy-independent variable b14 to separate neutrons from electrons via angular distributions. Allows one to reconstruct the energy profile of NC and CC events w/o use of energy constraint. Powerful check on the spectral shape of 8B Using Angular Information Monte Carlo Monte Carlo

  35. SNO during Construction

  36. Pee ~ 1-sin2(2q) sin2(1.27Dm2L / E) Physics: Dm2 & sin2(2q) Experiment: Distance (L) & Energy (E) Masses and Mixings ne ne ne nm nm nm nm

  37. hierarchical degenerate Higgs Field n n n t µ e Precision measurements! Three Pieces • For a full understanding of neutrino properties, it is necessary to determine: • The mixing parameters and phases • The neutrino masses • The physics governing mass

  38. CC 1967.7 +26.4 +49.5 +61.9 -60.9 -48.9 +25.6 ES 263.6 NC 576.5 Signal Extraction

  39. Summary of Backgrounds

  40. Status • All the NCDs are underground. • The 156 NCDs that will be deployed have been identified. • Pre-deployment welding is in progress. • The DAQ is operational and has been taking data from complete unwelded strings of NCDs underground. • All of the electronics are underground and operational. • The current estimated deployment date is October 2003, subject to removal of salt.

  41. Prediction from attenuation • 16N measured energy What is changing? Why? • Combination of both attenuation length and reflectors changing over time. • Change in optics accounts for why there was a large drop in energy response. • Attenuation length change correlated with change in water chemistry • Reflectors consistent with both a sudden drop in response, as well as a gradual decay. • Possible causes: petal degradation, temperature change

  42. Radon Spike • Further aim at understanding backgrounds to lower energy threshold. • Required to understand the detector uniformity and low energy tails. • Injection of 50 ml of solution at 25 grid points in vessel • 2.2 million Rn atoms/liter

  43. Energy response of the detector determined from 16N decay. Mono-energetic g at 6.13 MeV, accompanied by tagged b decay. Provides check on the optical properties of the detector. Radial, temporal, and rate dependencies well modeled by Monte Carlo. 16N Calibration Source

More Related