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

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

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

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

Solar Neutrino Physics with SNO (II) Spectrum 6 MeV13 MeV No. of CC events Increasing Δm 2 Day Night Day-Night Asymmetry: MSW SignaturesMSW Parameter Constraints hep-ph/ July Bandyopadhyay, Choubey, Goswami, Petcov, and Roy Global analysis of solar neutrino and KamLAND data from 2004 SNO measurements of CC/NC, spectrum, and day-night asymmetry contribute to MSW constraints “LMA region”

Pure D 2 OSalt 3 He Nov May 01 July 01 - Sep. 03 Nov 04 - Dec. 06 γ γ γ 35 Cl 36 Cl 36 Cl* n γ 2H2H 3H3H 3 H* n n captures on deuterium σ = b 6.25 MeV γ n captures on chlorine σ = 44b 8.6 MeV multiple γs n captures on 3 He in discrete prop. counter array σ = 5330b MeV n + 3 He  p + 3 H p 3H3H 5 cm n 3 He PRL 87, , 2001 PRL 89, , 2002 PRL 89, , 2002 PRL 92, , 2004 (for first 254 days) nucl-ex/ DAY RESULTS! Three ways to catch that neutron!

1. Higher capture cross-section means more neutrons detected 2. Boosts energy of NC events further above analysis threshold … 3H3H 36 Cl 2 H+n 35 Cl+n 6.25 MeV  = b  = 44 b 8.6 MeV Advantages of Salty D 2 O (I)

Define an “isotropy parameter” based on Legendre polynomials in θ ij 3. Multiple gammas for NC means light is more isotropic than for CC, ES  ij Advantages of Salty D 2 O (II) Statistical separation of CC, NC events with no constraint on the CC spectrum shape

20 EnergyIsotropy Direction Radius

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

391- day salt results !

Systematics Dominant systematic uncertainties for the shape-unconstrained analysis: Energy scale-0.9% +1.0%-3.3% +3.8%-1.6% +1.9% β 14 mean-4.0% +3.7%-3.6% +4.5%-1.2% +1.3% Radial scale-2.6% +2.5%-3.0% +3.3%-2.6% +3.0% Angular Res.-0.4% +0.4%-0.2% +0.2%-5.1% +5.1% CC NC ES For spectrum analysis: Systematic uncertainties evaluated in each extracted CC energy bin

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 8 B

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

A CC = ± (stat.) ± (syst.) A NC = ± 0.086(stat.) ± (syst.) A ES = ± 0.198(stat.) ± (syst.) (CC, ES spectrum shapes unconstrained in this analysis) Day-Night Asymmetries (I) A CC and A NC are correlated (ρ = ) In standard neutrino oscillations, A NC should be zero…

Day-Night Asymmetries (II) A CC = ± 0.063(stat.) ±0.032(syst.) A ES = ± 0.198(stat.) ±0.030(syst.) Constraining A NC to be zero: In the pure-D2O phase, (shape constrained, A NC constrained) Combine with analogous A CC from the salt phase: Convert Super-Kamiokande A ES to A e, and combine with SNO:

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

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

Conclusions Results from full 391-day salt phase available nucl-ex/ 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: