NDM03, June 9 2003 Mark Boulay for SNO Mark Boulay For the SNO Collaboration Los Alamos National...

Mark Boulay for SNO NDM03, June 9 2003

Mark Boulay

For the SNO Collaboration

Los Alamos National Laboratory, Los Alamos NM, 87544, USA

Present Status and Results from the SNO Experiment

•The SNO Detector and solar ’s•Results from the pure D2O Phase•Calibration for Salt (second) Phase Energy, Event Isotropy, Backgrounds•Signal Analysis in the Salt Phase (MC)•Projected sensitivity to mixing parameters•Conclusion and Outlook


The SNO CollaborationG. Milton, B. Sur

Atomic Energy of Canada Ltd., Chalk River Laboratories

S. Gil, J. Heise, R.J. Komar, T. Kutter, C.W. Nally, H.S. Ng,Y.I. Tserkovnyak, C.E. WalthamUniversity of British Columbia

J. Boger, R.L Hahn, J.K. Rowley, M. YehBrookhaven National Laboratory

R.C. Allen, G. Bühler, H.H. Chen*

University of California, Irvine

I. Blevis, F. Dalnoki-Veress, D.R. Grant, C.K. Hargrove,I. Levine, K. McFarlane, C. Mifflin, V.M. Novikov, M. O'Neill,

M. Shatkay, D. Sinclair, N. StarinskyCarleton University

T.C. Andersen, P. Jagam, J. Law, I.T. Lawson, R.W. Ollerhead,

J.J. Simpson, N. Tagg, J.-X. WangUniversity of Guelph

J. Bigu, J.H.M. Cowan, J. Farine, E.D. Hallman, R.U. Haq,J. Hewett, J.G. Hykawy, G. Jonkmans, S. Luoma, A. Roberge,

E. Saettler, M.H. Schwendener, H. Seifert, R. Tafirout,C.J. Virtue

Laurentian University

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

A. Schülke, A.R. Smith, R.G. StokstadLawrence Berkeley National Laboratory

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

R.G. Van de Water, J.B. Wilhelmy, J.M. Wouters Los Alamos National Laboratory

J.D. Anglin, M. Bercovitch, W.F. Davidson, R.S. Storey*

National Research Council of Canada

J.C. Barton, S. Biller, R.A. Black, R.J. Boardman, M.G. Bowler,J. Cameron, B.T. Cleveland, X. Dai, G. Doucas, J.A. Dunmore,

H. Fergani, A.P. Ferrarris, K. Frame, N. Gagnon, H. Heron, N.A. Jelley, A.B. Knox, M. Lay, W. Locke, J. Lyon, S. Majerus, G. McGregor,

M. Moorhead, M. Omori, C.J. Sims, N.W. Tanner, R.K. Taplin,M.Thorman, P.M. Thornewell, P.T. Trent, N. West, J.R. Wilson

University of Oxford

E.W. Beier, D.F. Cowen, M. Dunford, E.D. Frank, W. Frati,W.J. Heintzelman, P.T. Keener, J.R. Klein, C.C.M. Kyba, N. McCauley, D.S. McDonald, M.S. Neubauer, F.M. Newcomer, S.M. Oser, V.L Rusu,

S. Spreitzer, R. Van Berg, P. WittichUniversity of Pennsylvania

R. Kouzes

Princeton University

E. Bonvin, M. Chen, E.T.H. Clifford, F.A. Duncan, E.D. Earle,H.C. Evans, G.T. Ewan, R.J. Ford, K. Graham, A.L. Hallin,

W.B. Handler, P.J. Harvey, J.D. Hepburn, C. Jillings, H.W. Lee,J.R. Leslie, H.B. Mak, J. Maneira, A.B. McDonald, B.A. Moffat,

T.J. Radcliffe, B.C. Robertson, P. SkensvedQueen’s University

D.L. WarkRutherford Appleton Laboratory, University of Sussex

R.L. Helmer, A.J. NobleTRIUMF

Q.R. Ahmad, M.C. Browne, T.V. Bullard, G.A. Cox, P.J. Doe,C.A. Duba, S.R. Elliott, J.A. Formaggio, J.V. Germani,

A.A. Hamian, R. Hazama, K.M. Heeger, K. Kazkaz, J. Manor, R. Meijer Drees, J.L. Orrell, R.G.H. Robertson, K.K. Schaffer,

M.W.E. Smith, T.D. Steiger, L.C. Stonehill, J.F. Wilkerson University of Washington


Experiment Exp/SSMExperiment Exp/SSM

•SAGE+GALLEX/GNO 0.58SAGE+GALLEX/GNO 0.58

•Homestake 0.33 Homestake 0.33

•Kamiokande+SuperKKamiokande+SuperK 0.460.46

•SNO CC (June 2001) 0.35SNO CC (June 2001) 0.35

The Solar Neutrino ProblemThe Solar Neutrino Problem

Figure by J. Bahcall

SNO NC (April 2002) ~1

SNO CC vs NC implies flavor change, which can thenexplain other experimental results.


The SNO Detector

Nucl. Inst. and Meth. A449, p172 (2000)


Neutrino Reactions in SNO

- Q = 1.445 MeV- good measurement of e energy spectrum- some directional info (1 – 1/3 cos)- e only

- Q = 2.22 MeV - measures total 8B flux from the Sun- equal cross section for all types

NCxx

npd

ES e−e− x

- low statistics - mainly sensitive to e, some and

- strong directional sensitivity

CC e−ppd e

x


Solar Neutrino Physics with SNO

Electron neutrino energy spectrum Distortions in 8B spectrum?

What can we learn from measuring the NC interaction rate and the Day/Night variations of the 8B Flux?

Total 8B flux (NC) e flux (CC)

CCSNO/NCSNO Test of neutrino flavor change

Total flux of solar 8B neutrinos Test of solar models

Diurnal time dependence Test of neutrino oscillations


SNO’s response to neutron events (solar NC signal)

Phase I (pure D2O): Phase II (dissolved salt):

Phase III(3He n counters):

Past Present Future

Neutron capture on D

Single 6.25 MeV

n 3He p tNeutron capture on Cl

Multiple s, 8.6 MeV

Statistical separation(Energy, radius)

Statistical separation(Isotropy)

Independent channel

High CC-NC correlation Better CC-NC separation NC uncorrelated to CC


Statistical Signal Separation (D2O phase analysis)

•Signal PDFs used for statistical separation

)cos,,( sunCC ErF )cos,,( sunES ErF )cos,,( sunNC ErF

SNO response in eventradius, energy and directionto solar neutrinos throughCC, ES, and NC reactions

Maximum Likelihood fit for fluxes


CC 1967.7 +61.9 +60.9

+26.4 +25.6ES 263.6

+49.5 +48.9NC 576.5#EV

EN

TS

Shape Constrained Signal Extraction Results (Pure D2O phase)


Flux Results – Pure D2O Phase

)46.044.0()43.043.0(SNO

01.181.0SSM

09.505.5

12648.045.0

45.045.0

12609.009.0

05.005.0e

cm10.)(.)(41.3

cm10.)(.)(76.1

ssyststat

ssyststat

effect3.5

Constrained Fit forflavour change test

Without Constraint)55.057.1()58.057.1(SNO 42.6

Neutrinos change flavour


Physics Interpretation – Neutrino Oscillations SNO D2O results, pre-KAMLAND

SNO Day and Night Energy Spectra Alone

Combining All Experimentaland Solar Model information


Salt Phase Dataset (Analysis being completed now)

• Salt added to detector

• May 27, 2001 to October 10, 2002

• 503 days

• ~280 neutrino live-days (57.4%)• improved NC statistics• improved CC-NC separation from isotropy • Improved measurement of external neutron backgrounds

→ improved measurement of CC/NC ratio

→ precision unconstrained result


What We Measure

PMT MeasurementsPMT Measurements

-positionposition-chargecharge-timetime

Reconstructed EventReconstructed Event

--event vertexevent vertex-event direction-event direction-energy-energy-isotropy-isotropy


SNO Detector Calibration

Monte Carlo

CalibrationPulsersPulsed Laser16N3H(p,)4He8Li252CfU/Th

337nm to 620 nm6.13 MeV ’s19.8 MeV ’s <13.0 MeV ’sneutrons214Bi & 208Tl ’s

Cherenkov production (e-, )Photon propagation and detection

Neutron transport and captureReconstruction

(position, direction, energy, isotropy)


Vertex Reconstruction of EventsVertex Reconstruction of EventsN16

PMT times used to reconstruct event position

Resolution ~15 cm

UNTAGGEDUNTAGGED

TAGGEDTAGGED


Energy Calibration

Prompt time cut appliedto accept only direct photons

Reduces uncertainty due toscattering

Corrections for detector optics, dead PMTs, and gain applied

No. prompt hits vs. electron energy determined from MC calculations (SNOMAN EGS)


Energy Scale Calibration in Salt Phase

Relative gain from 16Ncalibration

MC

DataEnergy scale driftagrees with MC prediction

Due to small increasewith time in D2O photonabsorption.


Reponse to Neutrons in Salt

Capture on 35Cl 36Cl cascade•Multi-photon events isotropy•Energy peaks higher n 35Cl 36Cl (E = 8.6 MeV)

Signature of NC reaction


Encapsulated 252Cf Fission Source252Cf decays by emission or spontaneous fission.

Every fission produces 3.7676 0.0047* neutrons on average.

These neutrons capture on 35Cl and we observe the resulting gamma cascade, with the energy

distribution as shown.

’s accompanying the fission and ’s emitted by daughter products are removed using a timing cut.

* J.F. Wild, et al. Phys. Rev.,C41:640-646,1990

The Cf source is deployed in the detector encapsulated in an acrylic cylinder (height 2.5cm, radius 2.5cm).

SNO preliminary

*** Contributed by M. Kos ***


Event Isotropy Calibration in Salt Phase

16N calibrationsource

252Cf source

14

14

See next talk J. Dunmore


Neutron Response

Factor of ~3-4 increase in stats- larger capture cross-section - energy reponse peaks higher

Pure D2O

Volume weighted efficiency 14.38 +/- 0.53 %

Systematics Include:• energy scale and resolution• vertex reconstruction• source position• 252Cf source strength• burst selection• background

Salt

Preliminary

Volume weighted efficiency 41.3 x [1 +/- 0.038] %

Salt Phase

PRELIMINARYTotal Few Percent Level


In-Situ Background Measurement in Salt Phase


Fitting external source neutron backgrounds in salt

Monte-Carlo simulation

=(r/600)3 Maximum likelihood fit to extract external source neutron background events

Increased n captureefficiency on Cl allowsseparation of internaland external (background) sources of neutrons


Neutrino Flux Analysis for Salt Phase

Extended M

L Fit

NC E higher Less Rad. Sep.

DirectionalityUnchanged

Isotropy Separation

Variables: E, R3, cossun, 14

Signal Bkg

CerenkovPhotodis.

CCNCES}e

Fit Fix

Perturb ShiftVariables PDF’s

Fluxes

SystematicUncertainties

EnergyR3

cossunij

UnconstrainedUnconstrained

88B Shape ConstrainedB Shape Constrained

Statistical Signal Separation

14


Statistical Signal Separation Using Angular Information


Fit Result Uncertainties (Monte-Carlo)

Variables CC Stat. Error

NC Stat. Error

ES Stat. Error

E,R,sun 3.4% 8.6% 10%

E,R,sun 4.2% 6.3% 10%

E,R,sun,Iso 3.3% 4.6% 10%

R,sun,Iso 3.8% 5.3% 10%

D2O results

SimulatedSalt PhaseResults

Published D2O energy-unconstrained stat. Error was 24%

Simulations assume 1 yr of data with central values andcuts from D2O phase results


Projected Sensitivity to Mixing Parameters

Projectedsensitivity fromSNO salt phase

Projectedlimit onmaximal 1-2 mixing

Assuming D2Ophase NC result

Combined Solar + KAMLAND data

Figure adapted from Holanda and Smirnov, hep-ph/0212270


Summary

From pure D2O Phase (Phase I): Flavour Transformation Neutrinos Massive SSM agreement Combined Results: MSW Model -> LMA Favoured Region (now confirmed by KamLAND)From Salt Phase (Phase II): (expect this) Increased NC statistics – Additional Isotropy Separation Precision Fluxes without Shape ConstraintShape Constraint Improved CC/NC Measurement Model independent NC measurement Limit on 12, and on maximal mixing Currently finalizing systematics and analysis for salt phase datasetNext Phase (Phase III): NCDs soon Independent NC channel


The SNO CollaborationG. Milton, B. Sur

Atomic Energy of Canada Ltd., Chalk River Laboratories

S. Gil, J. Heise, R.J. Komar, T. Kutter, C.W. Nally, H.S. Ng,Y.I. Tserkovnyak, C.E. WalthamUniversity of British Columbia

J. Boger, R.L Hahn, J.K. Rowley, M. YehBrookhaven National Laboratory

R.C. Allen, G. Bühler, H.H. Chen*

University of California, Irvine

I. Blevis, F. Dalnoki-Veress, D.R. Grant, C.K. Hargrove,I. Levine, K. McFarlane, C. Mifflin, V.M. Novikov, M. O'Neill,

M. Shatkay, D. Sinclair, N. StarinskyCarleton University

T.C. Andersen, P. Jagam, J. Law, I.T. Lawson, R.W. Ollerhead,

J.J. Simpson, N. Tagg, J.-X. WangUniversity of Guelph

J. Bigu, J.H.M. Cowan, J. Farine, E.D. Hallman, R.U. Haq,J. Hewett, J.G. Hykawy, G. Jonkmans, S. Luoma, A. Roberge,

E. Saettler, M.H. Schwendener, H. Seifert, R. Tafirout,C.J. Virtue

Laurentian University

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

A. Schülke, A.R. Smith, R.G. StokstadLawrence Berkeley National Laboratory

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

R.G. Van de Water, J.B. Wilhelmy, J.M. Wouters Los Alamos National Laboratory

J.D. Anglin, M. Bercovitch, W.F. Davidson, R.S. Storey*

National Research Council of Canada

J.C. Barton, S. Biller, R.A. Black, R.J. Boardman, M.G. Bowler,J. Cameron, B.T. Cleveland, X. Dai, G. Doucas, J.A. Dunmore,

H. Fergani, A.P. Ferrarris, K. Frame, N. Gagnon, H. Heron, N.A. Jelley, A.B. Knox, M. Lay, W. Locke, J. Lyon, S. Majerus, G. McGregor,

M. Moorhead, M. Omori, C.J. Sims, N.W. Tanner, R.K. Taplin,M.Thorman, P.M. Thornewell, P.T. Trent, N. West, J.R. Wilson

University of Oxford

E.W. Beier, D.F. Cowen, M. Dunford, E.D. Frank, W. Frati,W.J. Heintzelman, P.T. Keener, J.R. Klein, C.C.M. Kyba, N. McCauley, D.S. McDonald, M.S. Neubauer, F.M. Newcomer, S.M. Oser, V.L Rusu,

S. Spreitzer, R. Van Berg, P. WittichUniversity of Pennsylvania

R. Kouzes

Princeton University

E. Bonvin, M. Chen, E.T.H. Clifford, F.A. Duncan, E.D. Earle,H.C. Evans, G.T. Ewan, R.J. Ford, K. Graham, A.L. Hallin,

W.B. Handler, P.J. Harvey, J.D. Hepburn, C. Jillings, H.W. Lee,J.R. Leslie, H.B. Mak, J. Maneira, A.B. McDonald, B.A. Moffat,

T.J. Radcliffe, B.C. Robertson, P. SkensvedQueen’s University

D.L. WarkRutherford Appleton Laboratory, University of Sussex

R.L. Helmer, A.J. NobleTRIUMF

Q.R. Ahmad, M.C. Browne, T.V. Bullard, G.A. Cox, P.J. Doe,C.A. Duba, S.R. Elliott, J.A. Formaggio, J.V. Germani,

A.A. Hamian, R. Hazama, K.M. Heeger, K. Kazkaz, J. Manor, R. Meijer Drees, J.L. Orrell, R.G.H. Robertson, K.K. Schaffer,

M.W.E. Smith, T.D. Steiger, L.C. Stonehill, J.F. Wilkerson University of Washington


Low Energy Calibration with 24Na

• A side benefit of NaCl addition is the ability to use 24Na as a low energy calibration source.

23Na + n 24Na

• n from a strong source via photodisintegration. The source is then removed and the 24Na decays away with T1/2 = 15 hours.

• The major advantage is that this source is containerless, removing concerns about shielding or container geometry.

• 24Na source helps validate performance of Monte Carlo at low energies.

Decay scheme here

24Na Decay scheme

SNO preliminary

24Na Decay Spectrum

MC+ Data


How Will the Salt Be Removed?

SNO’s reverse osmosis unit

The current run plan is to obtain 9 - 12 months oflivetime prior to salt removal.

• Salt will be removed using a reverse osmosis unit, which will produce a concentrated brine.

• The target is for ~1ppm salt in the D2O after multiple passes through the unit.

•At this level salt will not significantly affect neutron capture in the heavy water region.

Once the salt has been removed, SNO plans to continue with a short pure D2O run before entering the third phase of neutral current detection, when an array of 96 3He proportional counters will be installed into the detector.


Internal Radioactivity creates neutron background to the NeutralCurrent signal. The following table gives SNO’s aim for purity and the measured values of radioactivity in the D2O and in the salt:

•Before the salt was added to the D2O, it was purified by flow over MnOxand HTiO which reduced its Th and U concentrations by a factor of ~100.

•The radioactivity in the salt is not expected to significantly increase the background to the NC signal.

~ 2E-14 g /g salt D2O

1.8E-14 g /g D2O

< 4.5E-14 g /g salt D2O

238U

~ 3E-15 g /g salt D2O

1.6E-15 g /g D2O

< 3.7E-15 g /g salt D20

232Th

Salt D2O(preliminary)

Pure D2O(measured)

Goal (yields ~1 n/day)

*** Contributed by P. Jagam and B. Cleveland ***

Radioactivity and Background from Salted D2O


Detection

Electrons emit Čerenkov light, which is detected by the PMTs.

e

Neutrons are captured on 35Cl nuclei, which then emit a number of ’s

Comptonscatter

e'The ’s produce electrons through Compton scattering, or, less commonly, pair production or photoelectric absorption.

Distribution of no. ’s

(= 8.6 MeV)‘sn

36Cl*35Cl 36Cl

or on deuterium nuclei, as in the pure D2Ophase: n + d t + 6.25MeV (single )


Energy SystematicsSources Include:Detector StateStability 16N RunsOptical Model Radial/Asymmetry StudiesTiming

Total Uncertainty ~1-2%

Preliminary

Data – June 2001 scanData – May 2002 scanData – January 2003 scanMC – May 2002 scan


Calibration Radon Spike in SNO Detector

Rn injected into D2O region


Injectionbegan

InjectionEnded

t1/2=14.95 hrsC

ou

nts

-200 -100 0 100 200

24Na Background

Time Since Salt Injection (hrs)

Salt Injected on May 28, 2001

The NaCl brine in the underground buffer tank was activatedby neutrons from the rock wall. We observed the decay of 24Na after the brine is injected in the SNO detector.

External 24Na


Key signatures for oscillations

cc

es

=e

e + 0.154( +

cc

nc

e

e + + =

June 2001

April 2002

April 2002day nightvs

Measure total flux of solar neutrinos vs. the pure e flux

Evidencefor flavor change

Potential signalfor oscillations


24Na

24Mg

2.75 MeV

1.37 MeV

t1/2=14.95h

• A hot Th source is used to photodisintegrate the deuteron. The resulting neutrons activate the 23Na nuclei in the salt

• Used to test the low energy response of the detector, and to calibrate the light isotropy parameters used in the low energy background in-situ analysis

• Used to trace the water flow pattern in the ex-situ assay of radioactive backgrounds

Background Measurements in Salt Phase

Containerless source

NDM03, June 9 2003 Mark Boulay for SNO Mark Boulay For the SNO Collaboration Los Alamos National...

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