Welcome to SNOLAB And to the Neutrino Geoscience Conference Art McDonald Queen’s University,...

Welcome to SNOLABAnd to the Neutrino Geoscience

Conference

Art McDonaldQueen’s University, Kingston

Director, SNO Institute

(+)

The Enigmatic Neutrino

I have done a terrible thing. I have done a terrible thing.

I have postulated a particle that cannot be detectedI 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.

1948 Pontecorvo (Chalk River Report): Detection of Neutrinos from Reactors and the Sun

1950 Pontecorvo, Hanna: Neutrino mass limit from Tritium beta decay.

1956 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 8B 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 – 1948Bruno 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

+ 0.014Flux/SSM = 0.465 +- 0.005 - 0.012

Kamiokande (1000 tons), followed by

SuperKamiokande (50,000 tons)

Unique Signatures in SNO (D2O)

Charged-Current (CC)e+d e-+p+pEthresh = 1.4 MeV

ee onlyonly

Elastic Scattering (ES) (D2O & H2O)x+e- x+e-

x, but enhanced for e

Neutral-Current (NC) x+d x+n+p Ethresh = 2.2 MeV

Equally sensitive to Equally sensitive to e e

3 ways todetect neutrons

nepe

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 (3He)Nov. 04-Dec. 06

Phase I (D2O)Nov. 99 - May 01

SNO: 3 neutron (NC) detectionmethods (systematically different)

n captures on2H(n, )3H

Effc. ~14.4% NC and CC separation by energy, radial, and

directional distributions

40 proportional counters

3He(n, p)3HEffc. ~ 30% capture

Measure NC rate with entirely different

detection system.

2 t NaCl. n captures on35Cl(n, )36ClEffc. ~40%

NC and CC separation by event isotropy

36Cl

35Cl+n 8.6 MeV

3H

2H+n 6.25 MeV

n + 3He p + 3H

p3H

5 cm

n

3He

Acrylic vessel (AV) 12 m diameter

1700 tonnes H2O inner shielding

1000 tonnes D2O($300 million)

5300 tonnes H2O outer shielding

~9500 PMT’s

Creighton mineSudbury, CA

The Sudbury Neutrino Observatory: SNO6800 feet (~2km) underground

The heavy water has recently been returned and development work is in progress on SNO+ with liquid scintillator and 150Nd additive.

- Entire detectorBuilt as a Class 2000

Clean room- Low RadioactivityDetector 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, whoseopening angle is defined by the velocityof the particle.

However, it is the total light emitted thatprovides the accurate measure of particleenergy 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 showerand wears clean, lint-free clothing.

Over 70,000Showersto date andcounting

’s from 8Li ’s from 16N and t(p,)4He

252Cf 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, 24Na

Measuring U/Th Content Ex-situ Ion exchange (224Ra, 226Ra) Membrane Degassing (222Rn) Count daughter product decays

In-situ Low energy data analysis Separate 208Tl & 214Bi

Using Event isotropy

NeutronEvents

D2O H2O/AV

+8-944 +8

-827

SNO Phase 2 neutrino data: 391 live days with salt

Total Spectrum

hep-ex/0502021 March 2005

(NC)

“Blind” analysis of data

ISOTROPY: NC, CC separation

DIRECTION FROM SUN

EVENTS VS VOLUME: Bkg < 10%

ENERGY SPECTRUM FROM CC REACTION

NOOBSERVABLEDISTORTION

Heavy water

SNO Phase 2 with salt

)syst.()stat.( 35.2

)syst.()stat.( 94.4

)syst.()stat.( 68.1

15.015.0

22.022.0

38.034.0

21.021.0

08.009.0

06.006.0

ES

NC

CC

)scm10 of units(In 126

029.0031.0)stat.(023.034.0

NC

CC

Electron neutrinos

The Total Flux of Active

Neutrinos is measured

independently (NC) and agrees

well with solar model

Calculations:

5.82 +- 1.3 (Bahcall et al),

5.31 +- 0.6 (Turck-Chieze et al)

CC, NC FLUXESMEASURED

INDEPENDENTLY

Flavor change determined by > 7

Electron neutrinos areOnly 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+3He NCD Array

Neutral-Current Detectors (NCD): An array of 3He proportional counters

40 strings on 1-m grid~440 m total active length

Phase III production data taking Dec 2004 to Dec 2006. D2O 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

stat stat + systSNO 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

ijijijij

τττ

μμμ

eee

li

sandcwhere

cs

sc

iδecs

sccs

sc

UUU

UUU

UUU

U

sin,cos

0

010

0

00

010

001

0

0

001

100

0

0

1313

1313

2323

23231212

1212

321

321

321

ilil U If neutrinos have mass:

)E

LΔm.(θ)νP(ν eμ

222 271sin2sin

Solar,Reactor Atmospheric

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 Phase Reactor, Accel.

Range defined for m12, m23

Maki-Nakagawa-Sakata-Pontecorvo matrix

??

Solar + KamLAND fit results

m2 7.94 0.260.42 10 5 eV2

degrees4.13.112 8.33

)05(88 873.0 OPBSBBB

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 0607010 Periodic variations: [Variations < 8% (1 dy to 10 yrs)] hep-ex/0507079

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/0407029

Nucleon decay (“Invisible” Modes: N ) Phys.Rev.Lett. 92 (2004) [Improves limit by 1000]

Supernova Relic Electron Neutrinos hep-ex 0607010

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 WarningSystem: SNEWSA central computer wheresignals are sent byexperiments to look fora coincidence and alertthe astronomicalcommunity.

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