Sudbury Neutrino Observatory: Status and Future Plans Mark Chen Queen’s University ICFP2005, Chung-Li, Taiwan

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 = 1.44 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) Pure D 2 O “archival long paper” being prepared Salt Jul 01 – Sep 03 n  35 Cl  36 Cl   (E  = 8.6 MeV) enhanced NC and event isotropy PRL 92, (2004) nucl-ex/ “salt long paper” accepted for publication in Phys. Rev. C 3 He Counters Nov 04 – Dec 06 n  3 He  t  p proportional counters  = 5330 b event-by-event separation NCD data being taken see Melin Huang’s talk, Thurs afternoon

391-Day Salt Phase Flux Results   cc ( e ) = 1.68 (stat.) (syst.) × 10 6 cm −2 s −1   es ( x ) = 2.35 (stat.) (syst.) × 10 6 cm −2 s −1   nc ( x ) = 4.94 (stat.) (syst.) × 10 6 cm −2 s −1 BS05(OP) Standard Solar Model Flux Calculation: (5.69 ± 0.91) × 10 6 cm −2 s −1 (5.69 ± 0.91) × 10 6 cm −2 s − − − − − − −0.34

Oscillation Analysis 391-day Salt global solar plus latest KamLAND and 391-day SNO salt

Oscillation Analysis 391-day Salt global solar with 391-day SNO salt

SNO Timeline 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) – day/night and spectral shape are studied as well as the total active 8 B solar neutrino flux NCDs installed and taking production data; final SNO configuration offers CC and NC event-by-event separation, for improved precision and cleaner spectral shape examination ? we have learned a lot about solar neutrinos – but there is more to study and understand!

Fall 04 to Dec 06: SNO Phase III – 3 He proportional counter array now in place dedicated Neutral Current Detectors (NCDs) taking production data –data taking end date: 31 Dec 2006 will bring total uncertainty on 8 B solar NC signal below 5% –physics with heavy water will be complete –in 2007, heavy water will be returned to Atomic Energy of Canada Limited what should be done with the detector after? Beyond SNO

SNO plus liquid scintillator → physics program –pep and CNO low energy solar neutrinos tests the neutrino-matter interaction, sensitive to new physics –geo-neutrinos –240 km baseline reactor oscillation confirmation –supernova neutrinos –double beta decay? Fill with Liquid Scintillator

complete our understanding of neutrinos from the Sun pep, CNO, 7 Be explore the neutrino-matter interaction which is sensitive to new physics Low Energy Solar Neutrinos from Peña-Garay vacuum-matter transition best-fit oscillation parameters suggest MSW occurs but we have no direct evidence of MSW –day-night effect not observed –no spectral distortion for 8 B ’s

pep SNO CC/NC  m 2 = 8.0 × 10 −5 eV 2 tan 2  = 0.45 SSM pep flux: uncertainty ±1.5% known source → precision test Survival Probability Rise sensitive to new physics: non-standard interactions solar density perturbations mass-varying neutrinos CPT violation large  13 sterile neutrino admixture improves precision on  12 observing the rise confirms MSW and that we know what’s going on stat + syst + SSM errors estimated

3600 pep/year/kton >0.8 MeV 2300 CNO/year/kton >0.8 MeV 7 Be solar neutrinos using BS05(OP) and best-fit LMA Event Rates (Oscillated) resolution with 450 photoelectrons/MeV

non-standard interactions MSW is linear in G F and limits from -scattering experiments  g 2 aren’t that restrictive mass-varying neutrinos Friedland, Lunardini, Peña-Garay, hep-ph/ Barger, Huber, Marfatia, hep-ph/ pep solar neutrinos are at the “sweet spot” to test for new physics New Physics NC non-standard Lagrangian CHARM limit Miranda, Tórtola, Valle, hep-ph/ solar density fluctuations: Guzzo, Reggiani, de Holanda, hep-ph/ see also Burgess et al., hep-ph/

these plots from the KamLAND proposal muon rate in KamLAND: 26,000 d −1 compared with SNO: 70 d −1 11 C Cosmogenic Background

Real KamLAND Backgrounds external pep window

radiopurity requirements – 40 K, 210 Bi (Rn daughter) – 85 Kr, 210 Po (seen in KamLAND) not a problem since pep signal is at higher energy than 7 Be –U, Th not a problem if one can repeat KamLAND scintillator purity – 14 C not a problem since pep signal is at higher energy pep Solar Backgrounds

SNO+ pep SNOLAB is the only deep site that exists where the pep solar neutrinos could be measured with precision. pep solar neutrinos are a known source – enables a precision measurement (this is not the case with 7 Be). pp solar neutrinos are more difficult and may not reveal as much as pep (pp survival probability set by the average vacuum P ee ). First observation of the CNO solar neutrino would be important for astrophysics.

Geo-Neutrinos  can we detect the antineutrinos produced by natural radioactivity in the Earth? Image by: Colin Rose, Dorling Kindersley radioactive decay of heavy elements (uranium, thorium) produces antineutrinos assay the entire Earth by looking at its “neutrino glow” e

Earth’s Heat Flow  models of Earth’s heat sources suggest that radioactivity contributes % towards Earth’s total heat flow the radiogenic portion is not that well known! geophysicists want to understand Earth’s thermal history H.N. Pollack, S.J. Hurter and J.R. Johnson, Reviews of Geophysics 31(3), , 1993

Geo-Neutrino Signal terrestrial antineutrino event rates: Borexino: 10 events per year (280 tons of C 9 H 12 ) / 29 events reactor KamLAND: 29 events per year (1000 tons CH 2 ) / 480 events reactor SNO+: 64 events per year (1000 tons CH 2 ) / 87 events reactor the above plot is for Borexino…geo/reactor ratio in SNO+ would be twice as high KamLAND geo-neutrino detection…July 28, 2005 in Nature Rothschild, Chen, Calaprice (1998)

Fundamental Geophysics  SNO+ geo-neutrinos: a good follow-up to KamLAND’s first detection potential to really constrain the radiogenic heat flow potential to really constrain the radiogenic heat flow potential for geochemistry (U and Th separation) potential for geochemistry (U and Th separation) tests models of Earth’s chemical origin tests models of Earth’s chemical origin simple geological configuration (smaller uncertainties) simple geological configuration (smaller uncertainties)

1 kton organic liquid scintillator would maintain excellent supernova neutrino capability – e + p [large rate] – e + 12 C (CC) – x NC excitation of 12 C (NC) – x + p elastic scattering (NC) [large rate] see Beacom et al., PRD 66, (2002) Supernova Neutrinos

leverage existing investment in SNO to get new physics for relatively low cost SNO+ is uniquely positioned to make several measurements (due to depth, geology, appropriate distance to reactors, low backgrounds) costs are: –liquid scintillator procurement –mechanics of new configuration, AV certification –fluid handling and safety systems –scintillator purification –electronics/DAQ spares or upgrades? Extension of SNO Science

SNO+ Technical Issues  liquid scintillator selection compatibility with acrylic vessel compatibility with acrylic vessel high light yield, long attenuation length high light yield, long attenuation length  reversing the acrylic vessel mechanics SNO: AV contains heavy water, must hold up SNO: AV contains heavy water, must hold up SNO+: AV contains scintillator,  < 1 g/cm 3, must hold down SNO+: AV contains scintillator,  < 1 g/cm 3, must hold down  liquid scintillator purification

Acrylic Vessel Hold-down  “rope net” being designed to hold down 15% density difference (buoyancy) SNOSNO+

Scintillator Design  high density (>0.85 g/cm 3 )  chemical compatibility with acrylic  high light yield, long attenuation and scattering lengths  high flash point  low toxicity  low cost

Linear Alkylbenzene

LAB Advantages compatible with acrylic (e.g. Bicron BC-531 is 95% LAB) –“BC-531 is particularly suited for intermediate sized detectors in which the containers are fabricated with common plastic materials such as PVC and acrylics. The scintillator provides over twice the light output of mineral oil based liquids having similar plastic compatibility.” high flash point 130 °C low toxicity (pseudocumene 2 4 0) cheap, (common feedstock for LAS detergent) plant in Quebec makes 120 kton/year, supplier has been very accommodating high purity

SNO+ Monte Carlo light yield simulations KamLAND scintillator in SNO+ 629 ± 25 pe/MeV above no acrylic711 ± 27 pe/MeV KamLAND scintillator and 50 mg/L bisMSB 826 ± 24 pe/MeV above no acrylic 878 ± 29 pe/MeV KamLAND (20% PC in dodecane, 1.52 g/L PPO) ~300 pe/MeV for 22% photocathode coverage SNO+ has 54% PMT coverage; acrylic vessel only diminishes light ouput by ~10%

LAB Scintillator Optimization “safe” scintillators LAB has 75% greater light yield than KamLAND scintillator

Light Attenuation Length Petresa LAB as received attenuation length exceeds 10 m ~10 m preliminary measurement

Default Scintillator Identified LAB has the smallest scattering of all scintillating solvents investigated LAB has the best acrylic compatibility of all solvents investigated density  = 0.86 acceptable …default is Petresa LAB with 4 g/L PPO, wavelength shifter mg/L bisMSB because solvent is undiluted and SNO photocathode coverage is high, expect light output (photoelectrons/MeV) ~3× KamLAND

SNO+ is an NSERC-funded R&D project SNO+ endorsed by the SNOLAB Experiment Advisory Committee “Exploit low-energy solar neutrinos for precision neutrino physics and stellar physics” “We endorse development toward SNO+ for pep solar neutrinos and geo-neutrinos. We applaud the technical progress in developing the liquid scintillator and encourage continued R&D, development of the necessary collaboration and proposal to secure funding. We look forward to a receiving a full technical proposal.” SNO+ Status

SNO+ in 2006 SNO+ in Fall 2005 “proof of principle” –liquid scintillator identified –preliminary design to holddown the acrylic vessel need more collaborators project management scintillator purification R&D electronics/DAQ plans… full TDR by Fall 2006 –including process engineering and AV mechanics proposals to funding agencies by Fall 2006

SNO+ in 2007 start of capital funding construction of hold-down net access detector after D 2 O removed scintillator procurement contracts …and on to converting SNO into an operating, multi-purpose, liquid scintillator detector with unique physics capabilities

Queen’s M. Chen*, M. Boulay, X. Dai, K. Graham, A. Hallin, C. Hearns, C. Kraus, C. Lan, J.R. Leslie, A. McDonald, V. Novikov, P. Skensved, A. Wright, U. Bissbort, S. Quirk Laurentian D. Hallman, C. Virtue SNOLAB B. Cleveland, R. Ford, I. Lawson Brookhaven National Lab A. Garnov, D. Hahn, M. Yeh Los Alamos National Lab A. Hime LIP Lisbon J. Maneira potential collaborators from outside SNO (Italy, Germany, Russia) have indicated some interest new collaborators welcome SNO+ Collaboration only a subset of the SNO collaboration will continue with SNO+

SNO plus liquid scintillator plus double beta isotopes: SNO++ add  isotopes to liquid scintillator –dissolved Xe gas (2%) –organometallic chemical loading (Nd, Se, Te) –dispersion of nanoparticles (Nd 2 O 3, TeO 2 ) enormous quantities (high statistics) and low backgrounds help compensate for the poor energy resolution of liquid scintillator possibly source in–source out capability Double Beta Decay: SNO++

150 Nd 3.37 MeV endpoint (9.7 ± 0.7 ± 1.0) × yr 2  half-life measured by NEMO-III isotopic abundance 5.6% 1% natural Nd-loaded liquid scintillator in SNO++ has 560 kg of 150 Nd compared to 37 g in NEMO-III cost: $1/g for metallic Nd; cheaper as Nd salt…on the web NdCl 3 sold in lot sizes of 100 kg, 1 ton, 10 tons table from F. Avignone Neutrino 2004

2  Background good energy resolution needed but whopping statistics helps compensate for poor resolution and… turns this into an endpoint shape distortion measure rather than a peak search

0 : 1000 events per year with 1% natural Nd-loaded liquid scintillator in SNO++ Test = eV maximum likelihood statistical test of the shape to extract 0 and 2 components…~240 units of  2 significance after only 1 year! Klapdor-Kleingrothaus et al., Phys. Lett. B 586, 198, (2004) simulation: one year of data

Nd-carboxylate in Pseudocumene made by Yeh, Garnov, Hahn at BNL window with >6 m light attenuation length {

external 241 Am  Compton edge 137 Cs 207 Bi conversion electrons Nd LS Works!

Underground Facilities

Rectangular Hall 60’L x 50’W 50’ (shoulder) 65’ (back) Utility Drift Control Rm Staging Area Rectangular Hall SNOLAB Workshop IV, 15 Aug 2005

Wide Drift 20’x12’ (19’ to back) Wide Drift 25’x17’ (25’ to back) Access Drift 15’x10’ (15’ to back) Chemistry Lab Electrical, AHUs Ladder Labs SNOLAB Workshop IV, 15 Aug 2005

Underground Schedule Excavation Excavation Entry – now – 1 November Entry – now – 1 November Ladder – now – 1 November Ladder – now – 1 November Rectangular hall – 1 November – 9 May Rectangular hall – 1 November – 9 May Cryopit – 10 May – 1 December/06 Cryopit – 10 May – 1 December/06

Underground Schedule Outfitting Outfitting Finalize contract package – 30 September Finalize contract package – 30 September Award contract – 14 January Award contract – 14 January Entry 14Feb/06 – 13 June Entry 14Feb/06 – 13 June Ladder 14 June – 11 Oct Ladder 14 June – 11 Oct Rectangular hall 12 Oct – 8 February 07 Rectangular hall 12 Oct – 8 February 07

Surface Facility SNOLAB Workshop IV, 15 Aug 2005

SNOSolar Neutrinos SNO + & SNO ++Solar Neutrinos & Double Beta Decay Lithium DetectorSolar Neutrinos CLEANSolar Neutrinos & Dark Matter MajoranaDouble Beta Decay GerDADouble Beta Decay EXODouble Beta Decay COBRADouble Beta Decay SuperCDMSDark Matter ZEPLINDark Matter XENONDark Matter DEAPDark Matter PICASSODark Matter COUPPDark Matter DRIFTDark Matter Noble Liquid Tracking DetectorsSolar Neutrinos HALOSupernovae Neutrinos LENAProton Decay, Solar Neutrinos, Supernovae Neutrinos NOSTOS Neutrino Oscillations (  13 ) TRIGANeutron-Antineutron Oscillations Experimental Interest in SNOLAB

Depth Matters!

Experiment Advisory Committee Chair: Barry Barish Secretary: Andrew Hime Baha Balantekin (US) Cliff Burgess (CND) Ken Ragan (CND) John Martin (CND) Kate Scholberg (US) Takaaki Kajita (Japan) David Wark (UK) Scientific Merit Infrastructure Needs Progress on R&D Technical Feasibility Safety Funding & Schedule Participation & Management  Letters-of-Interest (LOI’s) received have undergone EAC review …  Letters-of-Response (LOR’s) have been drafted and distributed to points-of-contact …  LOR’s included a set of “Queries” to which (many) of you have responded …  Preliminary recommendations for the science program have been developed …  New considerations on the table since previous workshop and initial call for LOI’s  Use outcome of this workshop to refine vision and recommendations …  Feed-back Wednesday morning … August 17, 2005 at SNOLAB IV Workshop