Results (and Expectations) from SNO, the Sudbury Neutrino Observatory

Richard L. Hahn

PRC-US WorkshopBeijing, June 2006

*Research sponsored by the Office of Nuclear Physics, Office of Science, U.S. Department of Energy

Solar-Neutrino & Nuclear-Chemistry Group * Chemistry Department, BNL

Brookhaven Science AssociatesU.S. Department of Energy

Predicted Energy Spectra of Solar Neutrinos

from the Standard Solar Model (SSM)

Arrows Denote ExperimentalThresholds

71Ga 37Cl Water

LENS

Super-K, SNOSNO+

• Done:Done: HOMESTAKEHOMESTAKE Radiochemical Detector

C2Cl4; 37Cl + e 37Ar + e- (~40 years)

• Done:Done: GALLEX GALLEX Radiochemical Detector

Ga; 71Ga + e 71Ge + e- (1986 - 1998)

• NowNow:: SNO SNO Water Čerenkov Real-time Detector

Ultra-pure D2O (1996 - 2006) • New : #1 Focus for the FutureNew : #1 Focus for the Future THETA-13 THETA-13 High-Precision Experiments

at Daya Bay Nuclear Reactors Real-time Detector (R&D)

Gd in Liquid Scintillator, Gd-LS (began 2004)

• NewNew: : LENS LENS Real-time Detector (R&D) 115In-LS (began 2000), Detect pp and 7Be Solar Neutrinos• New:New: Very Long-Baseline Neutrino Oscillations Very Long-Baseline Neutrino Oscillations

Neutrino Beam from Accelerator (R&D began 2002)• New:New: SNOLab, SNO+ SNOLab, SNO+ (R&D) with LS (began 2005)

>40 Years of Neutrino R&D @ BNL Chemistry Dep’t.

Note: Hahn became Leader of BNL Group in 1986: GALLEX, SNO, 13

hBrookhaven Science AssociatesU.S. Department of Energy

BNL’s Ray Davis and His Discoveries

He was the first to observe neutrinos from the Sun. This was a very significant result, confirming our ideas of how stars produce energy. This was the basis of his 2002 Nobel Physics Prize. But, in a sense, we scientists expected that result. More exciting for us, he observed an unexpected result, too few neutrinos compared to the SSM. This anomaly became known as the Solar Neutrino Problem, and led to several important experiments; some were done by the BNL Solar-Neutrino Group. Ray Davis died May 31, 2006, at age 91+.Ray Davis died May 31, 2006, at age 91+.

Solar Neutrino Problem-”Disappearance”

PRE-SNO: Either

Solar Models are Incomplete and/or Incorrect, e.g., temperature of core is lower than expected,

OrNeutrinos undergo Flavor

Changing Oscillations (or other “New Physics”).

SOLAR FUSION: 4p 4He + 2e+ + 2e + 26 MeV

Kamiokande

Matter Enhanced Oscillations

SAGE & GALLEX

Homestake

LMA

LOW

SMA

MSW gives a dramatic extension of oscillation sensitivity to potential regions in m2

Solar data are consistent with the MSW hypothesis.

But prior to SNO, only had circumstantial evidence from Cl, Ga, Kamiokande, S-K; i.e.,

we knew thee disappeared.

• Needed definitive proof:

* Appearance measurement

* Independent of SSM

Enter The SNO CollaborationS.D. Biller, M.G. Bowler, B.T. Cleveland, G. Doucas,

J.A. Dunmore, H. Fergani, K. Frame, N.A. Jelley, S. Majerus, G. McGregor, S.J.M. Peeters, C.J. Sims, M. Thorman, H. Wan Chan Tseung, N. West, J.R. Wilson, K. Zuber

Oxford University

E.W. Beier, M. Dunford, W.J. Heintzelman, C.C.M. Kyba, N. McCauley, V.L. Rusu, R. Van Berg

University of Pennsylvania

S.N. Ahmed, M. Chen, F.A. Duncan, E.D. Earle, B.G. Fulsom,H.C. Evans, G.T. Ewan, K. Graham, A.L. Hallin, W.B. Handler,

P.J. Harvey, M.S. Kos, A.V. Krumins, J.R. Leslie, R. MacLellan, H.B. Mak, J. Maneira, A.B. McDonald, B.A. Moffat,

A.J. Noble, C.V. Ouellet, B.C. Robertson, P. Skensved, M. Thomas, Y.Takeuchi

Queen’s University

D.L. WarkRutherford Laboratory and University of Sussex

R.L. HelmerTRIUMF

A.E. Anthony, J.C. Hall, J.R. KleinUniversity of Texas at Austin

T.V. Bullard, G.A. Cox, P.J. Doe, C.A. Duba, J.A. Formaggio, N. Gagnon, R. Hazama, M.A. Howe, S. McGee,

K.K.S. Miknaitis, N.S. Oblath, J.L. Orrell, R.G.H. Robertson, M.W.E. Smith, L.C. Stonehill, B.L. Wall, J.F. Wilkerson

University of Washington

T. Kutter, C.W. Nally, S.M. Oser, C.E. WalthamUniversity of British Columbia

J. Boger, R.L. Hahn, R. Lange, M. YehBrookhaven National Laboratory

A.Bellerive, X. Dai, F. Dalnoki-Veress, R.S. Dosanjh, D.R. Grant, C.K. Hargrove, R.J. Hemingway, I. Levine, C. Mifflin, E. Rollin,

O. Simard, D. Sinclair, N. Starinsky, G. Tesic, D. WallerCarleton University

P. Jagam, H. Labranche, J. Law, I.T. Lawson, B.G. Nickel, R.W. Ollerhead, J.J. Simpson

University of Guelph

J. Farine, F. Fleurot, E.D. Hallman, S. Luoma, M.H. Schwendener, R. Tafirout, C.J. Virtue

Laurentian University

Y.D. Chan, X. Chen, K.M. Heeger, K.T. Lesko, A.D. Marino, E.B. Norman, C.E. Okada, A.W.P. Poon,

S.S.E. Rosendahl, R.G. StokstadLawrence Berkeley National Laboratory

M.G. Boulay, T.J. Bowles, S.J. Brice, M.R. Dragowsky, S.R. Elliott, M.M. Fowler, A.S. Hamer, J. Heise, A. Hime,

G.G. Miller, R.G. Van de Water, J.B. Wilhelmy, J.M. WoutersLos Alamos National Laboratory

Sudbury Neutrino Observatory, SNO

1700 tonnes InnerShielding H2O

1000 tonnes D2O

5300 tonnes Outer Shield H2O

12 m Diameter Acrylic Vessel

5-cm thick walls

Support Structure for 9500 PMTs, 60% coverage

Urylon Liner andRadon Seal

REAL

TIME

One million pieces transported down in the 10 foot square minecage and re-assembled underultra-clean conditions.

Brookhaven Science AssociatesU.S. Department of Energy

10

Reactions in SNO

NCxx

npd

ES -- ee xx

-Low Statistics -Mainly sensitive to e,, some

-sensitivity to and -Strong direction sensitivity

-Gives e energy spectrum well-Weak direction sensitivity 1-1/3cos()- e only.

-Measure total 8B flux from the sun.- Equal cross section for all types

CC-epd e p

Unique Feature: ‘Appearance’ of x vs. ‘Disappearance’ of e

Sensitive to 8B

Phase II (salt)July 01 - Sep. 03

Published

Phase III (3He)Summer 04 - Dec. 06

In Progress

Phase I (D2O)Nov. 99 - May 01

Published

SNO – used 3 neutron detection methods( 3 “different detectors” with possibly different systematics)

n captures on2H(n, )3H

= 0.0005 bObserve 6.25 MeV PMT array readout

Good CC

36 proportional counters3He(n, p)3H = 5330 b

Observe p and 3HPMT-independent

readout, event by event

2 t NaCl. n captures on35Cl(n, )36Cl

= 44 bObserve multiple ’sPMT array readout

Enhanced NC

36Cl

35Cl+n 8.6 MeV

3H

2H+n 6.25 MeV

n + 3He p + 3H

p3H

5 cm

n

3He

One raySeveral rays

X 1/3X 0.45

Signals in SNO (Monte Carlo, Renormalized)

~ 9 NHIT/MEV

Pure D2O Plus Salt

NC Salt (BP98)

Phase 2, NaCl:

Improved NC

Signal, 2003

Results

Phase 1, D2O:

2002 NC Results

SNO Energy Calibrations

’s from 8Li ’s from 16N and t(p,)4He

252Cf neutronsn d t … e

(E = 6.3 MeV)

6.13 MeV

19.8 MeV

NEUTRINO EVENT DISPLAYED ON SNO COMPUTER SYSTEM

Chemistry in SNOChemistry in SNO• Purify the water with respect to radioactivity and non-

radioactive chemical impurities.

• Ion Exchange & Ultrafiltration, MnOx, HTiO, Vacuum & Membrane De-gassing, Reverse Osmosis.

• Assay the water for residual contamination: Need to sample 100’s of tonnes in time period short compared to radioactive decay under study to reach sensitivity.

• Optical clarity.

• Biological Growth.

• Add or remove salt (Phase II).

• Maintain stability of water system: temperature, pressure,...

• Control D2O inventory and ratio of H2O/ D2O.

An important enemy, 232Th Decay Chain…..

s and s interfere with our signals at low energies

’s over 2.2 MeVfrom 208Tl d + n + p

Require 232Th content

< 3.7 x 10-15 g/g in D2O

Measure U/Th Backgrounds in D2O

• In-situ:– Low energy data

via Tl & Bi isotropy

• Ex-situ:– Ion exchange

(224Ra, 226Ra)

– Membrane degassing

– Count daughter product decays

SaltPhase

Several ’s in U and Th chains will photodisintegrate deuteron

Radon Calibration

Radial distributions for SNO Salt Data

(Reconstructed radius, cm/ 600)3

550 6000 700 cm

Sun-angle distributions for SNO Salt Data

Toward sun Away from sun points:

Energy Spectra Extracted from Salt DataWithout Imposing known 8B Shape

Electron kinetic energy

Flux Values

(Updated 2006)

(106 cm-2 s-1)

CC: 1.68(10)

ES: 2.35(27)

NC: 4.94(43)

Brookhaven Science AssociatesU.S. Department of Energy

Spectral Shapes are Extracted from the Salt Data, Not Assumed to Fit 8B

Shape Difference in CC Flux Between Unconstrained and 8B-Shape Constraint = 0.11 0.05(stat) +0.06

-0.09(syst)(units are 106 cm-2 s-1) Consistent with Hypothesis of No Spectral Distortion CC / NC = 0.306 0.026 (stat) 0.024 (syst) -e / total 1/3, -, / total 2/3 Result is independent of the solar model Results from Salt Phase, LMA Is Favored m2 = 7.1 X 10-5 ev2, 12 = 32.5o

SNO Results from Pure D2OSNO RESULTS, Salt + D2O391 live days

SNO SOLVED THE SOLAR NEUTRINO PROBLEM

SNO CC Result agreeswith Davis’Cl value.

Results from Other Exp’ts.

Measuring Neutrino Oscillation Parameters,Narrowing the Available Phase Space

Solar Neutrinos

Solar Neutrinos+ KamLAND 2003(e rate)

Agreement between oscillation parameters for and

Solar Neutrinos+ KamLAND 2004(e rate+spectrum)

‘Discovery Era in Neutrino Physics Is Finished, Entering Precision Era’

Solar (SNO)

e ,

Atmospheric (Super-K)

Reactor (KamLAND)

Accelerator (K2K)

• Neutrinos oscillate, must have mass

• Evidence for neutrino flavor conversion e

• SNO Solved Solar Neutrino Problem

H2O

D2OLS

m221 =7.8 10-5 eV2

12 =32

m232 =2.410-3 eV2

23 45

13 value UNKNOWN.From CHOOZ, only have limit, < 11° WHY SO SMALL?Want to measure with 1% precision.

Physics Motivation

Event-by-event separation. Measure NC and CC in separate data streams.

Different systematic uncertainties than neutron capture on NaCl.

NCD array removes neutrons from CC, calibrates remainder. CC spectral shape.

Detection Principle

2H + x p + n + x - 2.22 MeV (NC)

3He + n p + 3H + 0.76 MeV

x

n

40 Strings on 1-m grid

440 m total active length

NCD

PMT

SNO Phase III (NCD Phase)- Began 2004, To Finish End of 2006

3He Proportional Counters (“NC Detectors”)

Neutron Capture in the NCDs

~ 1200 n captures per year from solar

n + 3He p + 3H (Q = 764 keV)

p

3H

191 keV

573 keV 764 keV

3H

p

NCD wall

anode wire

Idealized energy spectrum in a 3He proportional counter. The main peak corresponds to the 764-keV Q-value of the 3He(n, p)3H reaction.

End view of an NCD with representative ionization tracks

p hits wall

3H hits wall

p-t track fully contained in gas

NCD Energy Spectrum

191-keV shoulder from proton going into the wall

764-keV peakEnergy spectrum from one deployed NCD string with an Am-Be neutron source.

Other Recent Work from SNO

Are analyzing NCD data (blind analysis) Are analyzing data on atmospheric muons and neutrinos Set new limit on hep flux, to be released very soon SNO is involved in SNEWS Published Periodicity Analysis of SNO data

- Did unbinned log likelihood analysis - No unknown solar period seen- Ruled out at 3.6 level the positive claim by

Sturrock et al. from their Super-K data analysis- Only variation that was seen was due to eccentricity of Earth’s orbit, measured = 0.0143 0.0086

Brookhaven Science AssociatesU.S. Department of Energy

THE FUTURE OF SNO

SNO finished Phase I, with Pure D2O, and Phase II, with NaCl + D2O; now running NCDs for ~2 years. Will end beginning of January 2007. All analyses done blind. New UG facility, “SNO Lab” is funded, being built. Are planning a relatively low-cost new experiment, “SNO+”, to use the existing SNO acrylic vessel, DAQ,and infrastructure; remove the D2O, refill with LS. Goal of SNO+ is to detect low-energy solar from pep and CNO solar branches; see Borexino, LENS… Want to see transition from matter-dominated to vacuum oscillations.

14m x 14m x 60m, Clean Area

SNOLAB

THE END

Thank you for your attention.