News from the Sudbury Neutrino Observatory Simon JM Peeters July 2007 o SNO overview o Results phases I & II o hep neutrinos and DSNB o Update on the III rd phase

Simon JM Peeters, June Acrylic vessel (AV) 12 m diameter 1700 tonnes H 2 O inner shielding 1000 tonnes D 2 O 5300 tonnes H 2 O outer shielding ~9500 PMTs, 54% coverage Creighton mine Sudbury, CA The Sudbury Neutrino Observatory (Herb Chen 1985: Use deuterium) "The Sudbury Neutrino Observatory", The SNO Collaboration Nuclear Instruments and Methods in Physics Research A449 (2000) pp feet (~2km) underground

Simon JM Peeters, June Neutrino reactions on D 2 O (sensitivity only to high energy component of solar s: 8 B and hep) CC : sensitive to electron neutrino flavour only. Electron energy directly correlated with energy. NC : sensitive to all neutrino flavours. ES : mostly electron flavour, direction (confirms origin solar e ) ~ 1o times smaller interaction cross section  NC    SSM  CC /  NC  P( e  e )

Simon JM Peeters, June The SNO program Comm. D2OD2O D2OD2O Salt (NaCl) 3 He Counters γ γ γ 35 Cl 36 Cl 36 Cl* n n captures on chlorine σ = 44b 8.6 MeV multiple γs n captures on 3 He prop. counter array σ = 5330b MeV n + 3 He  p + 3 H p 3H3H 5 cm n 3 He n captures on deuterium σ = b 6.25 MeV γ γ 2H2H 3 H* n 3H3H 306 days 391 days ~376 days (prelim)

Simon JM Peeters, June Neutrino flavour change, phase I PRL 87, , 2001 Direct Evidence for Neutrino Flavour Transformation: PRL 89, , 2002 PRL 89, , 2002 Measurement of the electron neutrino and total 8 B solar neutrino fluxes with the Sudbury Neutrino Observatory Phase 1 Data Set Phys. Rev. C 75, (2007) (76 pages)  SNO ES  SNO CC  SSM  SNO NC

Simon JM Peeters, June Neutrino flavour change, phase II oSalt analysis 1 Phys. Rev. C (2005) Electron Energy Spectra, Fluxes, and Day-Night Asymmetries of 8 B Solar Neutrinos from the 391-Day Salt Phase SNO Data Set. global fit result (inc day/night): Phys. Rev. Lett (2004)

Simon JM Peeters, June High(er) energy neutrinos: hep & DSNB (phase I data) hep neutrinos (SSM 8x10 3 cm -2 s -1 ) main background: 8 B solar neutrinos (normalize with low-energy (6-12 MeV) fit, taking into account neutrino oscillations) 2 events observed, consistent with exp. background (3.13±0.60) Φ hep < 2.3 x 10 4 cm -2 s -1 hep DSNB Astrophys. J. 653, 1545, 2006 DSNB el. neutrinos main background: atmospheric neutrinos No events observed, consistent with exp. background (0.18±0.04) Φ DSNB < 70 cm -2 s -1 (in E window)

Simon JM Peeters, June Phase III The Neutral Current Detection Array Array of 3 He (+CF 4 ) proportional counters to capture neutrons: avoids statistical separation CC/NC Geometry trade-off: ~8% light loss in centre vs ~ 26% capt. eff. Extremely low background (CVD nickel): ~65 alphas m -2 day -1 An array of low-background 3He proportional counters for the Sudbury Neutrino Observatory arXiv: [nucl-ex], accepted by NIMA. preliminary

Simon JM Peeters, June He neutron detection & calibration n captures on 3 He prop. counter array σ = 5330b MeV n + 3 He  p + 3 H p 3H3H 5 cm n 3 He Alpha Background Neutrons Fit Tail due to space charge and geometrical effects final analysis to include: pulse shape information geometrical event distribution (more info: poster B. Jamieson) No spherical symmetry: Replace point source calibration with uniform source: mix in 24 Na (2.7 MeV , T 1/2 =15 hrs) UNIFORM NEUTRON SOURCE

Simon JM Peeters, June The end game oPhase III analysis is ongoing (as well as analyses combining phases: neutrino flavour change, lower energy threshold analysis, periodicities, hep/DSNB, muons, exotic channels) oNCDs have been removed (possible future use) oD 2 O has been removed oState of detector examined for new experiment: SNO+

Simon JM Peeters, June The End

Simon JM Peeters, June

Simon JM Peeters, June Day-night analysis A = 2(  N -  D ) (  N +  D )  CC,ES asymmetry: e regeneration inside the Earth  NC asymmetry: Admixture of sterile neutrinos or unexpected matter interactions inside the Earth LMA: small A CC, A ES & A NC = 0 Combined with D2O phase and SK: A e = ± 0.027* (*NC=0, shape constr.)

Simon JM Peeters, June CC spectrum CC spectrum consistent with LMA, undistorted 8 B

Simon JM Peeters, June Calibrations energy (a.u.)

Simon JM Peeters, June Neutron calibration phase I, II

Simon JM Peeters, June Na calibration o 24 Na: 15 hr halflife, 2.7 MeV   n oTake brine, put in a reactor to produce 24 Na, inject into the world’s cleanest detector! oAccurately measure source strength oMix 1 ktonne quickly enough oSource of neutrons similar to NC oExpect O(2%) error on neutron capture efficiency PRELIMINARY