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New Results from the Salt Phase of SNO

New Results from the Salt Phase of SNO. Kathryn Miknaitis Center for Experimental Nuclear Physics and Astrophysics, Univ. of Washington For the Sudbury Neutrino Observatory. In this talk: SNO overview Salt phase overview

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New Results from the Salt Phase of SNO

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  1. New Results from the Salt Phase of SNO Kathryn Miknaitis Center for Experimental Nuclear Physics and Astrophysics, Univ. of Washington For the Sudbury Neutrino Observatory • In this talk: • SNO overview • Salt phase overview • New solar neutrino flux, spectrum, and day-night asymmetry results from 391 days of salt data! The Sudbury Neutrino Observatory

  2. The SNO Detector 6800 feet (~2km) underground Acrylic vessel (AV), 12 m diam. 1000 tonnes D2O 1700 tonnes H2O inner shielding 5300 tonnes H2O outer shielding ~9500 PMTs, 54% coverage

  3. Charged Current: • Detect the e- • energy spectrum • Weak directional sensitivity • Detect the n through secondary capture • No directional or neutrino energy info Neutral Current: • Detect the e- • Mainly sensitive to • Highly directional Elastic Scattering: SNO’s Three Reactions

  4. Solar Neutrino Physics with SNO (I) Measurement of the 8B Solar Neutrino Flux: Flavor Change Flavor change:

  5. Spectrum Increasing Δm2 No. of CC events Day 6 MeV 13 MeV Night Solar Neutrino Physics with SNO (II) MSW Signatures MSW Parameter Constraints hep-ph/0406328 July 21 2004 Bandyopadhyay, Choubey, Goswami, Petcov, and Roy Day-Night Asymmetry: “LMA region” Global analysis of solar neutrino and KamLAND data from 2004 SNO measurements ofCC/NC, spectrum, and day-night asymmetry contribute to MSW constraints

  6. n γ γ γ 36Cl* 35Cl 36Cl 5 cm n n γ 3H p 3H* 3He 2H 3H n + 3He  p + 3H Three ways to catch that neutron! Pure D2O Salt 3He Nov. 99 - May 01 July 01 - Sep. 03 Nov 04 - Dec. 06 n captures on deuterium σ = 0.0005b 6.25 MeV γ n captures on 3He in discrete prop. counter array σ = 5330b 0.764 MeV n captures on chlorine σ = 44b 8.6 MeV multiple γs PRL 92, 181301, 2004 (for first 254 days) nucl-ex/0502021 391-DAY RESULTS! PRL 87, 071301, 2001 PRL 89, 011301, 2002 PRL 89, 011302, 2002

  7. s = 44 b s = 0.0005 b 35Cl+n 2H+n 8.6 MeV 6.25 MeV 3H 36Cl Advantages of Salty D2O (I) 1. Higher capture cross-section means more neutrons detected 2. Boosts energy of NC events further above analysis threshold …

  8. Advantages of Salty D2O (II) qij 3. Multiple gammas for NC means light is more isotropic than for CC, ES Define an “isotropy parameter” based on Legendre polynomials in θij Statistical separation of CC, NC events with no constraint on the CC spectrum shape

  9. Energy Isotropy 20 Radius Direction

  10. 391- day salt results! 4722 events, r<550cm, Teff>5.5MeV Extracted Events: CC: 2176 ± 78 NC: 2010 ± 85 ES: 279 ± 26 External neutrons: 128 ± 42 Backgrounds fixed in fit: 128 (Patience! Energy spectrum coming up soon!)

  11. 391- day salt results!

  12. Systematics Dominant systematic uncertainties for the shape-unconstrained analysis: CC NC ES For spectrum analysis: Systematic uncertainties evaluated in each extracted CC energy bin

  13. CC Spectrum Extracted CC spectrum with statistical and systematic uncertainties Extracted CC spectrum with statistical uncertainties, compared to model predictions: CC spectrum consistent with LMA, undistorted 8B

  14. Systematics for the Day-Night Analysis DN Correlated Uncertainties: overall energy scale uncertainty… “cancel” in asymmetry ratio Differential Uncertainties: time variations (diurnal and long term) evaluate with in-situ techniques geometric uncertainties evaluate with calibration data Classes of Events Used to Limit Diurnal Variations: “Muon Followers”– neutrons induced by cosmic ray muons “Hot Spot” - radioactive spot on the acrylic vessel (AV) D2O radioactivity - uranium and thorium in the D2O H2O radioactivity - uranium and thorium in the H2O AV radioactivity - radioactive decays in the acrylic PMT beta - gammas from decays in the PMTs

  15. Day-Night Asymmetries (I) ACC= -0.056 ± 0.074 (stat.) ± 0.051 (syst.) ANC= 0.042 ± 0.086(stat.) ± 0.067 (syst.) AES= 0.146 ± 0.198(stat.) ± 0.032 (syst.) (CC, ES spectrum shapes unconstrained in this analysis) ACC and ANC are correlated (ρ = -0.532) In standard neutrino oscillations, ANC should be zero…

  16. Day-Night Asymmetries (II) Constraining ANC to be zero: ACC= -0.037 ± 0.063(stat.) ±0.032(syst.) AES= 0.153 ± 0.198(stat.) ±0.030(syst.) Combine with analogous ACC from the salt phase: Convert Super-Kamiokande AES to Ae, and combine with SNO: In the pure-D2O phase, (shape constrained, ANC constrained)

  17. Global Solar, with new salt results Global Solar + KamLAND 766 ton-year data MSW Constraints Previous global analysis of solar neutrino data

  18. x n SNO Phase III (NCD Phase) • 3He Proportional Counters (“NC Detectors”) now installed • Production data taking underway 40 Strings on 1-m grid 440 m total active length Detection Principle 2H + x p + n + x - 2.22 MeV (NC) 3He + n  p + 3H + 0.76 MeV PMT Physics Motivation Event-by-event separation. Measure NC and CC in separate data streams. Different systematic uncertainties than neutron capture on NaCl. NCD

  19. Conclusions • Results from full 391-day salt phase available nucl-ex/0502021 • Solar neutrino flux results confirm and improve previous results • CC spectrum presented, consistent with LMA prediction (also consistent with no distortion) • Day-Night asymmetries consistent with LMA prediction (also with no asymmetry) • MSW mixing parameters:

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