SNO Review & Comparisons NOW September 2004 Mark Chen Queen’s University & The Canadian Institute for Advanced Research

The SNO Collaboration T. Kutter, C.W. Nally, S.M. Oser, C.E. Waltham 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 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. 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, 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. Wark Rutherford Laboratory and University of Sussex R.L. Helmer TRIUMF A.E. Anthony, J.C. Hall, J.R. Klein 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, R.G.H. Robertson, M.W.E. Smith, L.C. Stonehill, B.L. Wall, J.F. Wilkerson University of Washington

1000 tonnes D 2 O 12 m diameter Acrylic Vessel 18 m diameter support structure; 9500 PMTs (~60% photocathode coverage) 1700 tonnes inner shielding H 2 O 5300 tonnes outer shielding H 2 O Urylon liner radon seal depth: 2092 m (~6010 m.w.e.) ~70 muons/day Sudbury Neutrino Observatory

Neutrino Reactions in SNO - Q = MeV - good measurement of e energy spectrum - some directional info  (1 – 1/3 cos  ) - e only - Q = 2.22 MeV - measures total 8 B flux from the Sun - equal cross section for all active flavors NC xx    npd ES    e−e− e−e− x - low statistics - mainly sensitive to e, some  and  - strong directional sensitivity CC e−e− ppd  e x

SNO Neutral Current Trilogy Pure D 2 O Nov 99 – May 01 n  d  t   (E  = 6.25 MeV) good CC PRL 87, (2001) PRL 89, (2002) PRL 89, (2002) “D 2 O Archival Long Paper” in progress Salt Jul 01 – Sep 03 n  35 Cl  36 Cl   (E  = 8.6 MeV) enhanced NC and event isotropy PRL 92, (2004) “Long Salt Paper” soon to be submitted 3 He Counters Fall 04 – Dec 06 n  3 He  t  p proportional counters  = 5330 b event-by-event separation “First NCD Paper” in the future

Physics Motivation Event-by-event separation. Measure NC and CC in separate data streams. Different systematic uncertainties than neutron capture on NaCl. 3 He array removes neutrons from CC, calibrates remainder. CC spectral shape. Detection Principle 2 H + x  p + n + x MeV (NC) 3 He + n  p + 3 H MeV 40 Strings on 1-m grid 398 m total active length x n NCD PMT SNO Phase III: 3 He Detectors 3 He Proportional Counters (“NC Detectors”)

Structure of this Talk – Comparison of Phases signals backgrounds energy and optics flux spectral shape day-night analysis oscillation analysis

Čerenkov Detection PMT Measurements -position -charge -time Reconstructed Event -event vertex -event direction -energy-isotropy

Signal Extraction Pure D 2 O signal PDFs –energy –R 3 (radius) –cos  Sun Monte Carlo maximum likelihood fit with background amplitudes fixed

energy R3R3 cos  Sun statistical signal separation – extended maximum likelihood  14 event isotropy use R 3, cos  Sun,  14 perform signal extraction w/o any spectral shape assumptions Signal Extraction Salt Phase

higher capture cross section higher energy release many gammas n 36 Cl * 35 Cl 36 Cl  3H3H 2 H+n 35 Cl+n 6.3 MeV 8.6 MeV  = b  = 44 b NaCl Neutron Detection

35 Cl(n,  ) 36 Cl  = ± T e ≥ 5.5 MeV and R  ≤ 550 cm 2 H(n,  ) 3 H  = ± T e ≥ 5.0 MeV and R  ≤ 550 cm Neutron Capture Efficiency 2 tonnes of NaCl added to 1000 tonnes heavy water 252 Cf fission neutron source

Simulated Neutron Event in D 2 O neutron events in pure D 2 O look very similar to single electrons

Simulated Neutron Event in Salt neutron events in salt are more isotropic

Čerenkov Light and  14 ) 43 o e − (v > c/n) hollow cone of emitted photons energy & direction  ij       sum over all pairs of PMT hits

Monte Carlo Signal Separation

Neutron Signals from the First NCD data taken on the J3 string (first 9.5 m long NCD) with the AmBe source on 12/02/03 at 22:38 EST bin 135 is about 764 keV total number of neutrons in the peak roughly matches Monte Carlo prediction

Comparison of Phases signals backgrounds energy and optics flux spectral shape day-night analysis oscillation analysis

Sources of Background  + d → p + n, from 214 Bi (U chain), 208 Tl (Th chain) cosmic rays: neutrons, spallation products atmospheric neutrinos, reactors, CNO electron capture fission (U, Cf) ( ,n) reactions 24 Na activation (neck, calibration, recirculation, muons) AV events focus is on neutron backgrounds to the NC

Pure D 2 O Water Assays targets for D 2 O represent a 5% background from  + d  n + p targets are set to reduce  -  events reconstructing inside 6 m

Salt Phase Water Assays bottom of vessel 2/3 way up top of vessel MnO x HTiO MnO x HTiO salted D 2 O radioactivity should produce 0.72 ± 0.24 neutrons per day pure D 2 O radioactivity was estimated at 1.0 ± 0.2 neutrons per day the SSM rate of NC events would produce 13.1 neutrons per day

New Salt Phase Background 24 Na activation neutrons activate 23 NaCl…salty D 2 O can be activated outside the detector and brought in by circulation 24 Na 24 Mg 2.75 MeV 1.37 MeV  + d → p + n NC background and low-energy  ’s t 1/2 = hr

External 24 Na Introduced The NaCl brine in the underground buffer tank was activated by neutrons from the rock wall. We observed the decay of 24 Na after the brine is injected in the SNO detector. Salt Injected on May 28, Na Background t 1/2 =14.95 hrs

External Neutrons light water  ’s photodisintegrate deuteron radon daughters deposited on the acrylic vessel during construction 210 Pb has t 1/2 = 22 years feeds 210 Po which alpha decays ( ,n) on 13 C, 17 O, 18 O neutrons originate from the AV pure D2O phasesalt phase estimated from radioassays, 27 ± 8 events subtracted was not considered fit both

Fitting External Neutron Backgrounds  =(R [cm]/600) 3 improved separation of internal and external background neutrons efficient neutron capture on Cl

SourceNumber of Events deuteron photodisintegration H( ,  )pn 2.8 ± ,18 O( ,n) 1.4 ± 0.9 fission, atmospheric ’s 23.0 ± 7.2 terrestrial and reactor ’s 2.3 ± 0.8 neutrons from rock <1 24 Na activation 8.4 ± 2.3 neutrons from CNO ’s 0.3 ± 0.3 total internal neutron background ± 25 internal  (fission, atmospheric ) 5.2 ± N decays< 2.5 (68% CL) external-source neutrons (from fit) 84.5 ± 34 Čerenkov events from PMT  -  <14.7 (68% CL) “AV events”< 5.4 (68% CL) Salt Phase Backgrounds Table −25.5

NCD Backgrounds: Pulse Shape  track  wire De-logged current Time (microseconds) current preamplifiers digitize pulse shapes for particle identification

Comparison of Phases signals backgrounds energy and optics flux spectral shape day-night analysis oscillation analysis

manipulator positioning accuracy: ~2 cm laserball moved throughout detector (in two planes) extract optical parameters (D 2 O attenuation, PMT angular response, H 2 O attenuation) at various wavelengths B. Moffat with dye laser and laserball Optical Calibrations

16 N Calibration Source internally triggered used for: energy scale energy drift detector radial response energy resolution vertex resolution angular resolution M. Boulay with 16 N source O 16 N 7.13 s −− 26% 68% 5% 1%

Detector Energy Drift

Monitoring Detector Optics D 2 O attenuation increasing water chemistry analyses reveal increasing Mn and organics consistent with light absorption feature at ~420 nm

Salt Energy Scale Drift energy scale drift agrees with MC prediction coming from slight increase in D 2 O photon absorption over time…

Desalination started 09/09/2003 pass #1 completed 09/14/2003…100x reduction reverse osmosis

Pass #1 Stratification salt probe conductivity measurement purified D 2 O floats salt interface remained solid throughout operation salt water more dense probe z position [cm]

Na and Impurities Removed feed permeate LimitFeedPermeate Mn <2 ppb ~15 ppb ~0.1 ppb Cr <1 ppb ~0.6 ppb ~0.04 ppb Fe <1.5 ppb <10 ppb <1.5 ppb Ni <20 ppb <0.8 ppb <0.08 ppb Cu <40 ppb <3 ppb <1 ppb TOC<10 ppb ~20 ppb ~3-4 ppb

Optics Restored – Confirmation! −1.8% per year due to D 2 O attenuation desalination pass #1 Mn and/or TOC light absorption removed! salt phase energy drift

Optics Destroyed! in NCD Phase example of a current NCD phase optics calibration occupancy map from laserball source in the centre of the detector working now to understand the detector (PMT’s and NCD’s)

Comparison of Phases signals backgrounds energy and optics flux spectral shape day-night analysis oscillation analysis

CC ES NC #EVENTS SNO Pure D 2 O Results (2002) 1 st paper threshold days neutron background: 78 primarily  + d → p + n Čerenkov background: − −12

 e = 1.76(stat.)(syst.) × 10 6 cm −2 s −1   = 3.41(stat.)(syst.) × 10 6 cm −2 s −1 Constrained Shape Fluxes   cc ( e ) = 1.76 (stat.) (syst.) × 10 6 cm −2 s −1   es ( x ) = 2.39 (stat.) (syst.) × 10 6 cm −2 s −1   nc ( x ) = 5.09 (stat.) (syst.) × 10 6 cm −2 s −1 E threshold > 5 MeV * *E >2.2 MeV − − − − − − − − − −0.45 more than just e coming from the Sun!

CC ES NC #EVENTS Salt Phase neutrino live-days Energy Spectra Light Isotropy Radial Sun-angle dist.

SNO Salt Fluxes shape of 8 B spectrum in CC and ES not constrained: standard (Ortiz et al.) shape of 8 B spectrum in CC and ES:   cc ( e ) = 1.76 (stat.) (syst.) × 10 6 cm −2 s −1   es ( x ) = 2.39 (stat.) (syst.) × 10 6 cm −2 s −1   nc ( x ) = 5.09 (stat.) (syst.) × 10 6 cm −2 s − − − − − − −0.43 compare with pure D 2 O

internal neutrons energy scale resolution radial accuracy angular resolution isotropy mean isotropy width radial E bias Čerenkov bkds “AV” events neutron capture total Uncertainties in Fluxes (%)

Total Active 8 B Fluxes in units of Bahcall, Pinsonneault, Basu 2001 SSM, 5.05 x 10 6 cm −2 s −1 BPB01 SSM1.00 Junghans et al. nucl-ex/ ± 0.16 BP04 SSM1.15 ± 0.26 SNO D 2 O (constrained) 1.01 ± 0.13 SNO D 2 O (unconstrained) 1.27 ± 0.33 SNO Salt (unconstrained) 1.03 ± −0.16 new S 17 results are consistent with SSM and with each other uncertainty in total flux reduced in the new salt result, even while constraints were relaxed

Next Salt Paper: Fluxes days to days, increased statistics improved systematics determinations (does not mean all systematics have become smaller!)

NCD Phase: Fluxes D 2 O unconstrained D 2 O constrained Salt unconstrained 3 He NC,CC ~0 CC,ES ~-0.2 ES,NC ~0 good statistics CC, NC break correlations smaller systematic uncertainties

Comparison of Phases signals backgrounds energy and optics flux spectral shape day-night analysis oscillation analysis

Pure D 2 O Energy Spectrum  m 2 = 8 × 10 −5 eV tan 2  Day Spectrum CC+NC+ES would be worse with salt

Salt Extracted CC Spectral Shape CC Spectral Shape recoil electron total energy [MeV] rate/SSM  m 2 = 8 × 10 −5 eV 2 tan 2 

Salt CC Spectral Systematics bin-bin statistical correlations from likelihood extraction and for various systematics determined most systematics are small for the integrated CC flux measurement…but, not necessarily small in each spectral bin energy dependence and biases investigated and understood to be presented soon in the upcoming paper

NCD Phase Spectra 3 He counters “soak up” the neutrons will allow a cleaner look at low energy CC events will still be some neutron captures by deuterons in the heavy water; these can be calibrated and subtracted using the NCD neutron count rate

Comparison of Phases signals backgrounds energy and optics flux spectral shape day-night analysis oscillation analysis

Pure D 2 O Day-Night Spectra night − day define asymmetry: A = 2 (N – D) (N + D)  A cc = 14.0 ± −1.4  A nc = −20.4 ± −2.5  e = 7.0 ± −1.2 night rate: 9.79 ± 0.24 d −1 day rate: 9.23 ± 0.27 d −1

Can SNO Observe Day-Night Effect? tan 2  3.3 % Bahcall, Gonzalez-Garcia, Peña-Garay +5.7 − % +1.1 − % in CC

Comparison of Phases signals backgrounds energy and optics flux spectral shape day-night analysis oscillation analysis

Oscillations Analysis: Before SNO before SNO Fogli, Lisi, Montanino Palazzo after SNO Pure D 2 O SNO Collaboration this figure updated and upgraded

Oscillation Analysis: Global Solar Before Salt After Salt --90% --95% --99% %

Oscillation Analysis Before LMA LOW pre-salt solarsolar plus KamLAND Bahcall, Gonzalez- Garcia, Peña-Garay LMA-I LMA-II

Oscillation Analysis After Salt −90% −95% −99% −99.73% LMA-I only at > 99% CL solarsolar plus KamLAND global solar finds only LMA

Salt PRL Fluxes + New KamLAND including KamLAND Neutrino 2004 results log-log plot in tan 2 

Synopsis of SNO Salt Results oscillation parameters, 2-D joint 1  boundary marginalized 1-D 1  errors LMA-I favored at >99% C.L. maximal mixing rejected at 5.4  sin 2  12 = 0.29 ± 0.04 next salt paper oscillation analysis will include salt day-night, CC spectral shape…

Global Solar NCD Projection with and w/o KamLAND SNO will constrain the mixing angle... lin-lin plot in tan 2 

Comparison of Phases signals backgrounds energy and optics flux spectral shape day-night analysis oscillation analysis

Summary commissioning Pure D 2 O Salt Pure D 2 O and desalination 3 He Counters NOW added 2 ton of NaCl pure D 2 O phase discovers active solar neutrino flavors that are not e salt phase moves to precision determination of oscillation parameters; flux determination has no spectral constraint (thus can use it rigorously for more than just the null hypothesis test) NCDs installed and about to begin production data taking; final SNO configuration offers CC and NC event-by-event separation, for improved precision and cleaner spectral shape examination

fin