The Sudbury Neutrino Observatory.

Neil McCauleyUniversity of Pennsylvania

NuFact 0427th July 2004

Summary

Introduction to SNO. Solar Neutrino Analysis. Other Physics Topics. Deployment and Commissioning of 3He

Proportional Counters. Conclusions.

The SNO Collaboration

T. Kutter, C.W. Nally, S.M. Oser, T. Tsui, C.E. Waltham, J.Wendland

University 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. Waller

Carleton University

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

University of Guelph

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

Laurentian University

Y.D. Chan, X. Chen, C. Currat, 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

S.D. Biller, M.G. Bowler, B.T. Cleveland, G. Doucas, J.A. Dunmore, H. Fergani, K. Frame, N.A. Jelley, J.C. Loach, S. Majerus, G. McGregor, S.J.M. Peeters,

C.J. Sims, M. Thorman, H. Wan Chan Tseung, N. West, J.R. Wilson, K. ZuberOxford University

E.W. Beier, H. Deng, M. Dunford, W. Frati, W.J. Heintzelman, C.C.M. Kyba, N. McCauley, M.S Neubauer, V.L. Rusu, R. Van Berg, P. Wittich

University of Pennsylvania

S.N. Ahmed, M. Chen, F.A. Duncan, E.D. Earle, H.C. Evans, G.T. Ewan, B. G Fulsom, K. Graham, A.L. Hallin, W.B. Handler, P.J. Harvey, L.L Kormos, M.S. Kos, C.B. Krauss, 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, M. Huang, J.R. Klein, S. SeibertUniversity 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,

K. Rielage, R.G.H. Robertson, M.W.E. Smith, L.C. Stonehill, B.L. Wall, J.F. Wilkerson

University of Washington

The Sudbury Neutrino Observatory

2039m to surface

1000 tonnes of D2O

7000 tonnes of H2O

Norite rock

6800 ft level

INCO’s Creighton Mine

Sudbury, Ontario

12m diameter acrylic vessel

17m diameter PMT support structure with ~9500 PMTs

Urylon liner and radon seal

Signals in SNO Charged Current

D+ep+p+e-

Electron energy closely corresponds to neutrino energy. Weak directional sensitivity.

CC=e

Neutral Current D+xp+n+x

Equally sensitive to all active neutrino flavors. Threshold 2.2MeV.

NC=e +

Elastic Scattering e-+xe-+x

Good directional sensitivity. Enhanced e sensitivity.

ES=e + 0.154

Where is the physics? Solar Neutrinos:

Measure mixing parameters. Measure CC/NC ratio

Measures 12.

Search for direct signatures of neutrino oscillation.

Day – Night Asymmetry Spectral Distortions.

Rare solar neutrino searches. Solar Antineutrinos Neutrinos from the hep reaction.

Other Physics: Atmospheric Neutrinos Proton Decay Neutron – Antineutron

Oscillations. Supernovae.

Taken from hep-ph/0406328

Note the linear scale.

10-4

6x10-5

The Phases of SNO. Phase 1: Pure D2O.

Nov 1999 – May 2001 : 306.4 days. Neutrons Capture on D

Need spectral information to separate CC and NC.

Phase 2: D2O+NaCl Jul 2001-Sep 2003 : ~ 391 days. Neutrons Capture on 35Cl

Statistically separate neutrons and electrons via event isotropy.

Phase 3: 3He Counters (NCD) 2004-Dec 2006 Neutrons capture on 3He

Event by event separation of neutrons and electrons.

Why add salt? Increase in Capture

Cross Section. Increase in visible

Cerenkov energy. Increased Neutron

Statistics. Detection efficiency:

14.4% → 39.9% Multiple g-rays in the

final state. Can statistically

separate neutron events from electrons using event isotropy.

Event Isotropy. Decompose the

hit pattern into spherical harmonics.

Choose the combination that best separates CC and NC. 14=1+44

Uncertainty on 14 mean 0.87%

Backgrounds Radioactive Backgrounds

U Chain – 214Bi Th Chain – 208Tl Sodium Activation – 24Na

Neutrons. Cherenkov Tail.

(,n) reactions on carbon. External Neutrons.

Cosmogenic Neutrons from atmospheric neutrinos.

Instrumental Backgrounds

New Calibration: controlled Radon spike.

Now include external neutrons as a free parameter in the fit.

Signal Extraction – Phase 1 Maximum Likelihood

fit to PDFs. Variables:

Teff

(R/RAV)3

cos()

Background PDFs fixed.

New PDFsES NCCC

E/MeV

(r/600cm)3

cos()

14

The Changes for the salt phase require new PDFs Now have 4 variables

with the addition of 14.

CC/ES PDFs unchanged.

New NC PDF Update to signal

extraction 14 depends upon

energy 2D PDFs.

Addition of external neutrons to the fit.

Salt Results – 254 livedays. Results from July01-Oct02. Spectrum for CC and ES

unconstrained. Blind Analysis. Fit for external neutrons.

Kinetic Energy

Radius Direction Isotropy

Flux Measurements.Salty D2O Pure D2O

)sys()stat(21.2Φ 10.010.0-

+0.310.26-ES

+=

)sys()stat(76.1Φ 09.009.0-

+0.060.05-CC

+=

)sys()stat(39.2Φ 12.012.0-

+0.240.23-ES

+=

)sys()stat(09.5Φ 46.043.0-

+0.440.43-NC

+=

Unit x106 cm-2s-1

)sys()stat(59.1Φ 06.008.0-

+0.080.07-CC

+=

)sys()stat(21.5Φ 38.038.0-

+0.270.27-NC

+=

Upcoming Salt Results. Use the full salt data set.

~391 days. ~176 days during the day. ~214 days during the night.

Same energy threshold as the first salt paper (T=5.5MeV).

Also include Day – Night Results. Full Spectral Analysis.

Long paper in preparation.

Other Physics TopicsSNO can search from more than solar neutrinos……

Invisible Nucleon Decay Limits. For invisible nucleon decay in 16O

Can search for excitation s.

Comparing the pure D2O and salt phases

inv>1.9x1029 years for neutron modes. inv>2.1x1029 years for proton modes.

PRL 92, 102004, 2004

Vanishing Neutron6.18MeV 44%BR 7.03MeV 2%BR

Vanishing Proton6.32MeV 41%BR7.00MeV 4%BR

Anti Neutrino Search. Look for

e+D → e++n+n

Q=4.03MeV Double and triple coincidence

search. nn coincidence threshold at

4.03MeV Direct Detection. Low Reactor background at SNO. Pure D2O Results.

e < 3.4x104cm-2s-1 (90%CL) hep-ex/0407029 Not competitive with KamLand

e < 3.7x102cm-2s-1 (90%CL)

SNO Limits.

SK Limits.

Phase 3: The NCD phase. Use 3He proportional

counters. Uniquely identify neutron

events. 3He+n→p+T

Measure Charge vs Time in the proportional counters.

40 Strings on 1 m grid. Total Active length 398m.

Expect capture efficiency:

~25% on 3He ~20% on D

Aim to measure CC/NC to ~7%

Signals in the NCDs. Digitize the charge vs

time signal from the NCDs. Neutron events have

two particles. Radioactive

backgrounds have one. Neutron Free Window

in charge vs rise time. Benchtest Data. 4He Strings provide

control sample.

New Analysis Challenges NCD Data

Calibration. Instrumental

Backgrounds. Separation of neutron

signal from alpha background.

Understanding end effects.

Z position from reflection.

System deadtime. External neutrons.

PMT Data Light occultation from

NCDs. U/Th in/on the NCDs. Understanding/checking

previous analysis inputs Reconstruction Energy Isotropy Event Selection Cuts

Signal Extraction. Loss of spherical symmetry. Constraints on neutrons

from NCDs.

From Salt to NCDs. NCD Configuration Optimization: End of Salt Phase: End of Salt Removal: End of Second Pure D2O Phase: First NCD deployed: Last String Deployed: Removal of Deployment

Hardware: Commissioning of Manipulator: End of Commissioning Phase:

Sep-Dec 2002

28 Aug 2003

3 Oct 2003

27 Oct 2003

3 Dec 2003

12 Feb 2004

23 Apr 2004

Jun 2004

Oct 2004

The Second Pure D2O Phase. The second pure D2O

phase was used to verify the return to baseline. Optical Response. Energy Scale.

Cleaning of the water. Mn Organics

Neutron Response.

Extensive period of calibration.

Start of Salt Removal

NCD Deployment

12 m

7 m

GlobalViewCamera

NCD

Deck Clean Room

HauldownSystem

Boathook

CableAttachmentRing

Shuttle Float

PulleyFloat

GVC Controls

D2O Level

BoathookHandle

HauldownCrank

AnchorAttachmentSite

3He Counters Radio Purity <10ppt U/Th.

500X Cleaner than best previous detectors.

Development and construction 1991-2004.

Anchors deployed during AV construction.

To Deploy NCDs. Attach counter to hauldown

mechanism. Use ROV to bring counter in the

D2O. Laser weld additional counters to

string above the neck. Leak test and test with Neutron

Source. Attach to anchor point. Secure Cable Repeat.

NCD Deployment

NCD Commissioning. Learn about the new

detector. Calibration Instrumental Backgrounds. Interaction of NCD and PMT

systems. Learn how to run the

detector. Are the NCDs running OK?

What to look for. Updates to monitoring tools.

Automation of procedures NCD electronics calibration. Data Processing. Data Flow.

Aim to finish commissioning in the autumn.

A Neutron Event

A “Fork” Event

Conclusions SNO Results:

Solve the solar neutrino problem and demonstrate neutrino flavour change.

Restrict the measured values of the solar mixing parameters.

Future results can help further restrain the mixing parameters, particularly 12.

The NCD array is deployed in the detector. Commissioning of the full system now

underway.

The Solar Neutrino Problem

Neutrino Flavor Change?

Something else?

Measuring Cherenkov Tails :

A Radon Spike Calibration.

+ Monte Carlo for Th and Na

Compare with pure D2O measurement.