Welcome to SNOLAB And to the Neutrino Geoscience Conference Art McDonald Queen’s University, Kingston Director, SNO Institute (+)

The Enigmatic Neutrino I have done a terrible thing. I have postulated a particle that cannot be detected. W. Pauli 1930

Neutrinos, along with electrons and quarks are the basic particles of nature that we do not know how to sub-divide further. Neutrinos come in three types (electron, mu, tau) as described in The Standard Model of Elementary Particles, the accepted basic theory of particle physics. They have a mass, but it is more than 5 million times smaller than an electron. Neutrinos are made in very large numbers in the nuclear reactions that power the Sun. Neutrinos only stop if they hit the nucleus of any atom or an electron head-on. They can pass through a light- year of lead without stopping. Therefore they are very difficult to detect and far less is known about them than the other basic particles. Anti-neutrinos are created in the beta decays such as U and Th and in nuclear reactors. Geo-neutrinos are electron anti-neutrinos. What are Neutrinos?

A short summary of Neutrino History 1914 Continuous Beta Spectra Observed: Chadwick 1930 Pauli invents the neutrino to save Energy Conservation 1933 Fermi baptizes the “neutrino”: The Little Neutral one Pontecorvo (Chalk River Report): Detection of Neutrinos from Reactors and the Sun 1950 Pontecorvo, Hanna: Neutrino mass limit from Tritium beta decay Reines & Cowan observe electron anti-neutrinos from a reactor 1957 Pontecorvo: Postulates Neutrino Oscillations 1962 Lederman, Schwartz, Steinberger observe muon neutrinos 1968 Solar Neutrino flux is too low: Davis measurements with Chlorine, Bahcall calculations 1968 Solar Neutrino Oscillations?: Pontecorvo 1974 Discovery of Electroweak neutral currents via neutrino beams 1987 Neutrinos from Supernova 1987a: IMB, Kamiokande 1989 Low Solar Neutrino 8 B flux: Kamiokande with water 1992 Low solar neutrino pp flux: Gallex, SAGE with Gallium 1991 LEP experiments show that there are only three light neutrinos 1998 Atmospheric muon neutrino disappearance: Super-Kamiokande

First Tennis Champion at Chalk River – 1948 Bruno Pontecorvo

relic supernova neutrinos hep solar neutrinos Neutrino fluxes at the Earth

Bahcall et al., SNO Solving “The Solar Neutrino Problem” Solar Model Flux Calculations CNO SNO was designed to observe separately e and all neutrino types to determine if low e fluxes come from flavor change or solar models Previous Experiments Sensitive to Electron Neutrinos

Flux/SSM = Kamiokande (1000 tons), followed by SuperKamiokande (50,000 tons)

Unique Signatures in SNO (D 2 O) Charged-Current (CC) e +d  e - +p+p E thresh = 1.4 MeV e only e only Elastic Scattering (ES) (D 2 O & H 2 O) x +e -  x +e - x, but enhanced for e Neutral-Current (NC) x + d  x + n+p E thresh = 2.2 MeV Equally sensitive to e   3 ways to detect neutrons

Anti-neutrino detection in a material with hydrogen The neutron subsequently is thermalized and captured by a proton producing a 2.2 MeV gamma, so there is a few msec time coincidence with the positron.

Phase II (salt) July 01 - Sep. 03 Phase III ( 3 He) Nov. 04-Dec. 06 Phase I (D 2 O) Nov May 01 SNO: 3 neutron (NC) detection methods (systematically different) n captures on 2 H(n,  ) 3 H Effc. ~14.4% NC and CC separation by energy, radial, and directional distributions 40 proportional counters 3 He(n, p) 3 H Effc. ~ 30% capture Measure NC rate with entirely different detection system. 2 t NaCl. n captures on 35 Cl(n,  ) 36 Cl Effc. ~40% NC and CC separation by event isotropy 36 Cl 35 Cl+n 8.6 MeV 3H3H 2 H+n 6.25 MeV n + 3 He  p + 3 H p 3H3H 5 cm n 3 He

Acrylic vessel (AV) 12 m diameter 1700 tonnes H 2 O inner shielding 1000 tonnes D 2 O ($300 million) 5300 tonnes H 2 O outer shielding ~9500 PMT’s Creighton mine Sudbury, CA The Sudbury Neutrino Observatory: SNO 6800 feet (~2km) underground The heavy water has recently been returned and development work is in progress on SNO+ with liquid scintillator and 150 Nd additive. - Entire detector Built as a Class 2000 Clean room - Low Radioactivity Detector materials

Cerenkov Light  = v/c Cerenkov Light is emitted whenever a charged particle exceeds the phase velocity of light in a medium. Example electrons in water: The light is emitted in a cone, whose opening angle is defined by the velocity of the particle. However, it is the total light emitted that provides the accurate measure of particle energy in SNO and SuperK.

SNO: One million pieces transported down in the 9 ft x 12 ft x 9 ft mine cage and re-assembled under ultra-clean conditions. Every worker takes a shower and wears clean, lint-free clothing. Over 70,000 Showers to date and counting

 ’s from 8 Li  ’s from 16 N and t(p,  ) 4 He 252 Cf neutrons 6.13 MeV 19.8 MeV Energy calibrated to ~1.5 % Throughout detector volume Optical calibration at 5 wavelengths with the “Laserball” SNO Energy Calibrations: 25% of running time + AmBe, 24 Na

Measuring U/Th Content Ex-situ  Ion exchange ( 224 Ra, 226 Ra)  Membrane Degassing ( 222 Rn) Count daughter product decays In-situ  Low energy data analysis  Separate 208 Tl & 214 Bi Using Event isotropy Neutron Events D2OD2OH 2 O/AV

SNO Phase 2 neutrino data: 391 live days with salt Total Spectrum hep-ex/ March 2005 (NC) “Blind” analysis of data

ISOTROPY: NC, CC separation DIRECTION FROM SUN EVENTS VS VOLUME: Bkg < 10% ENERGY SPECTRUM FROM CC REACTION NO OBSERVABLE DISTORTION Heavy water SNO Phase 2 with salt

Electron neutrinos   The Total Flux of Active Neutrinos is measured independently (NC) and agrees well with solar model Calculations: (Bahcall et al), (Turck-Chieze et al) CC, NC FLUXES MEASURED INDEPENDENTLY Flavor change determined by > 7  Electron neutrinos are Only about 1/3 of total!

Final Phase: SNO Phase III Search for spectral distortion in CC Improve solar neutrino flux by breaking the CC and NC correlation: CC: Cherenkov Signal  PMT Array NC: n+ 3 He  NCD Array Neutral-Current Detectors (NCD): An array of 3 He proportional counters 40 strings on 1-m grid ~440 m total active length Phase III production data taking Dec 2004 to Dec D 2 O now removed.

Very low Background. About one count per 2 hours in region of interest. To be reduced in future analyses by pulse shape discrimination. Blind Data: Include hidden fraction of neutrons that follow muons and omit an unknown fraction of candidate events until all analysis parameters fixed

statstat + syst SNO Fluxes: 3 Phases p-value for consistency of NC/CC/ES in the salt & NCD phases + D2O NC(unconstr) is 32.8%

Direct observation (7  ) of neutrino flavor change via an appearance measurement: Neutrino Physics Beyond the Standard Model for Elementary Particles. Direct measurement (10 % accuracy) of total flux of active solar neutrinos: Strong confirmation of Solar Models. With Kamland: Strong confirmation of neutrino oscillation due to finite mass (MNSP mechanism) as the primary physics explanation for appearance and disappearance measurements. With other solar measurements: Strong evidence for Matter Enhancement of oscillations in the Sun. Summary of SNO results

If neutrinos have mass: Solar,ReactorAtmospheric The most favored explanation for the data to date is: Neutrino Oscillations of 3 active massive neutrino types For two neutrino oscillation in a vacuum: (valid approximation in many cases) CP Violating PhaseReactor, Accel. Range defined for  m 12,  m 23 Maki-Nakagawa-Sakata-Pontecorvo matrix ? ?

Solar + KamLAND fit results eV 2 degrees Impact on models for neutino properties (Smirnov summary at Neutrino 2008) Tri-Bi-Maximal Mixing: 35.2 deg Quark-Lepton Complementarity: 32.2 deg (  12 +  Cabbibo = 45 deg)

SNO Physics Program Solar Neutrinos (6 papers to date)  Electron Neutrino Flux  Total Neutrino Flux  Electron Neutrino Energy Spectrum Distortion  Day/Night effects  hep neutrinos hep-ex  Periodic variations: [Variations < 8% (1 dy to 10 yrs)] hep-ex/ Atmospheric Neutrinos & Muons  Downward going cosmic muon flux  Atmospheric neutrinos: wide angular dependence [Look above horizon] Supernova Watch (SNEWS) Limit for Solar Electron Antineutrinos hep-ex/ Nucleon decay (“Invisible” Modes: N ) Phys.Rev.Lett. 92 (2004) [Improves limit by 1000] Supernova Relic Electron Neutrinos hep-ex

For an event at the Center of the Galaxy SNO would observe ~1000 events evenly Distributed among Electron, mu, tau Neutrinos, SuperK about 5000 events, mostly anti- e Supernova Early Warning System: SNEWS A central computer where signals are sent by experiments to look for a coincidence and alert the astronomical community. X