The Sudbury Neutrino Observatory. Neil McCauley University of Pennsylvania NuFact th July 2004

Summary  Introduction to SNO.  Solar Neutrino Analysis.  Other Physics Topics.  Deployment and Commissioning of 3 He 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. Yeh Brookhaven 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. Stokstad Lawrence 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. Wouters Los 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. Zuber Oxford 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. Wark Rutherford Laboratory and University of Sussex R.L. Helmer TRIUMF A.E. Anthony, J.C. Hall, M. Huang, J.R. Klein, S. Seibert University 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 D 2 O 7000 tonnes of H 2 O 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+ e  p+p+e -  Electron energy closely corresponds to neutrino energy.  Weak directional sensitivity.  CC = e  Neutral Current D+ x  p+n+ x  Equally sensitive to all active neutrino flavors.  Threshold 2.2MeV.  NC = e +    Elastic Scattering e - + x  e - + x  Good directional sensitivity.  Enhanced e sensitivity.  ES = e  

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/ Note the linear scale x10 -5

The Phases of SNO.  Phase 1: Pure D 2 O. Nov 1999 – May 2001 : days. Neutrons Capture on D  Need spectral information to separate CC and NC.  Phase 2: D 2 O+NaCl Jul 2001-Sep 2003 : ~ 391 days. Neutrons Capture on 35 Cl  Statistically separate neutrons and electrons via event isotropy.  Phase 3: 3 He Counters (NCD) 2004-Dec 2006 Neutrons capture on 3 He  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 +4 4  Uncertainty on  14 mean 0.87%

Backgrounds  Radioactive Backgrounds U Chain – 214 Bi Th Chain – 208 Tl Sodium Activation – 24 Na  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: T eff (R/R AV ) 3 cos(  )  Background PDFs fixed.

New PDFs ESNCCC 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 RadiusDirectionIsotropy

Flux Measurements. Salty D 2 OPure D 2 O Unit x10 6 cm -2 s -1

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 Topics SNO can search from more than solar neutrinos……

Invisible Nucleon Decay Limits.  For invisible nucleon decay in 16 O Can search for excitation s. Comparing the pure D 2 O and salt phases  inv >1.9x10 29 years for neutron modes.  inv >2.1x10 29 years for proton modes.  PRL 92, , 2004 Vanishing Neutron 6.18MeV 44%BR 7.03MeV 2%BR Vanishing Proton 6.32MeV 41%BR 7.00MeV 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 D 2 O Results. e  < 3.4x10 4 cm -2 s -1 (90%CL) hep-ex/ Not competitive with KamLand  e  < 3.7x10 2 cm -2 s -1 (90%CL) SNO Limits. SK Limits.

Phase 3: The NCD phase.  Use 3 He proportional counters. Uniquely identify neutron events.  3 He+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 3 He ~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. 4 He 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 Aug Oct Oct Dec Feb Apr 2004 Jun 2004 Oct 2004

The Second Pure D 2 O Phase.  The second pure D 2 O 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 Global View Camera NCD Deck Clean Room Hauldown System Boathook Cable Attachment Ring Shuttle Float Pulley Float GVC Controls D 2 O Level Boathook Handle Hauldown Crank Anchor Attachment Site  3 He Counters Radio Purity <10ppt U/Th.  500X Cleaner than best previous detectors. Development and construction  Anchors deployed during AV construction.  To Deploy NCDs. Attach counter to hauldown mechanism. Use ROV to bring counter in the D 2 O. 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 D 2 O measurement.