Sudbury Neutrino Observatory Status and Future Plans ICFP

Sudbury Neutrino Observatory: Status and Future Plans ICFP 2005, Chung-Li, Taiwan Mark Chen Queen’s University

Sudbury Neutrino Observatory 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

Neutrino Reactions in SNO CC n e d p p e− - Q = 1. 44 Me. V - good measurement of ne energy spectrum - some directional info (1 – 1/3 cosq) - ne only NC n x d p n n x - Q = 2. 22 Me. V - measures total 8 B n flux from the Sun - equal cross section for all active n flavors ES n x e− - low statistics - mainly sensitive to ne | some n and n - strong directional sensitivity

SNO Neutral Current Trilogy Pure D 2 O Salt 3 He Nov 99 – May 01 Jul 01 – Sep 03 Nov 04 – Dec 06 n d t g n 35 Cl 36 Cl g n 3 He t p (Eg = 6. 25 Me. V) (E g = 8. 6 Me. V) good CC enhanced NC and event isotropy PRL 87, 071301 (2001) PRL 89, 011301 (2002) PRL 89, 011302 (2002) Pure D 2 O “archival long paper” being prepared Counters proportional counters s = 5330 b event-by-event separation PRL 92, 181301 (2004) nucl-ex/0502021 “salt long NCD data being taken paper” accepted for publication in Phys. Rev. C see Melin Huang’s talk, Thurs afternoon

391 -Day Salt Phase Flux Results +0. 06 +0. 08 +0. 22 +0. 15 +0. 21 +0. 38 Fcc(ne) = 1. 68 − 0. 06 (stat. ) − 0. 09(syst. ) × 106 cm− 2 s− 1 Fes(nx) = 2. 35 − 0. 22 (stat. ) − 0. 15(syst. ) × 106 cm− 2 s− 1 Fnc(nx) = 4. 94 − 0. 21 (stat. ) − 0. 34(syst. ) × 106 cm− 2 s− 1 BS 05(OP) Standard Solar Model Flux Calculation: (5. 69 ± 0. 91) × 106 cm− 2 s− 1

Oscillation Analysis 391 -day Salt global solar plus latest Kam. LAND and 391 -day SNO salt

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

SNO Timeline 1998 1999 commissioning 2000 2001 2002 2003 2004 2005 2006 NOW Pure D 2 O Salt 3 He added 2 ton of Na. Cl Counters Pure D 2 O and desalination • pure D 2 O phase discovers active solar neutrino flavors that are not ne we have learned a lot about solar neutrinos – but there is more to study and understand! • 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 ?

Beyond SNO • 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 n 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?

Fill with Liquid Scintillator • 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?

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

Survival Probability Rise stat + syst + SSM errors estimated SSM pep flux: uncertainty ± 1. 5% Dm 2 = 8. 0 × 10− 5 e. V 2 tan 2 q = 0. 45 known source → precision test improves precision on q 12 sensitive to new physics: • non-standard interactions • solar density perturbations • mass-varying neutrinos • CPT violation • large q 13 • sterile neutrino admixture SNO CC/NC pep n observing the rise confirms MSW and that we know what’s going on

Event Rates (Oscillated) 7 Be resolution with 450 photoelectrons/Me. V solar neutrinos 3600 pep/year/kton >0. 8 Me. V using BS 05(OP) and best-fit LMA 2300 CNO/year/kton >0. 8 Me. V

New Physics NC non-standard Lagrangian • non-standard interactions • MSW is linear in GF and limits from n-scattering experiments g 2 aren’t that restrictive • mass-varying neutrinos CHARM limit Friedland, Miranda, Lunardini, Peña-Garay, hep-ph/0402266 Tórtola, Valle, hep-ph/0406280 solar density fluctuations: Guzzo, Reggiani, de Holanda, hep-ph/0302303 also Burgess et at al. , hep-ph/0310366 pep solarsee neutrinos are the “sweet spot” to test for new physics Barger, Huber, Marfatia, hep-ph/0502196

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

Real Kam. LAND Backgrounds external pep window

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

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 Pee). First observation of the CNO solar neutrino would be important for astrophysics.

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

Earth’s Heat Flow Ø models of Earth’s heat sources suggest that radioactivity contributes 40 -100% 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), 267 -280, 1993

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

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

Supernova Neutrinos • 1 kton organic liquid scintillator would maintain excellent supernova neutrino capability – – – ne + p ne + 12 C (CC) nx NC excitation of 12 C (NC) nx + p elastic scattering (NC) [large rate] see Beacom et al. , PRD 66, 033001(2002)

Extension of SNO Science • 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?

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

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

Scintillator Design Ø high density (>0. 85 g/cm 3) Ø chemical compatibility with acrylic Ø high light yield, long attenuation and scattering lengths Ø high flash point Ø low toxicity Ø 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. ” • • 1 high flash point 130 °C 1 0 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 Kam. LAND scintillator in SNO+ 629 ± 25 pe/Me. V above no acrylic 711 ± 27 pe/Me. V Kam. LAND scintillator and 50 mg/L bis. MSB 826 ± 24 pe/Me. V above no acrylic 878 ± 29 pe/Me. V Kam. LAND (20% PC in ~300 pe/Me. V for 22% dodecane, 1. 52 g/L PPO) 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 Kam. LAND scintillator

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

Default Scintillator Identified • LAB has the smallest scattering of all scintillating solvents investigated • LAB has the best acrylic compatibility of all solvents investigated • density r = 0. 86 acceptable • …default is Petresa LAB with 4 g/L PPO, wavelength shifter 10 -50 mg/L bis. MSB • because solvent is undiluted and SNO photocathode coverage is high, expect light output (photoelectrons/Me. V) ~3× Kam. LAND

SNO+ Status • 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+ 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

SNO+ Collaboration Queen’s M. Chen*, M. Boulay, X. Dai, K. Graham, A. Hallin, C. Hearns, C. Kraus, C. Lan, J. R. Leslie, A. Mc. Donald, V. Novikov, P. Skensved, A. Wright, U. Bissbort, S. Quirk Laurentian D. Hallman, C. Virtue SNOLAB B. Cleveland, R. Ford, I. Lawson only a subset of the Brookhaven National Lab SNO collaboration will A. Garnov, D. Hahn, M. Yeh continue with SNO+ 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

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

150 Nd table from F. Avignone Neutrino 2004 • 3. 37 Me. V endpoint • (9. 7 ± 0. 7 ± 1. 0) × 1018 yr 2 nbb 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 Nd. Cl 3 sold in lot sizes of 100 kg, 1 ton, 10 tons

2 n bb 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

Test <mn> = 0. 150 e. V 0 n: 1000 events per year with 1% natural Nd-loaded liquid scintillator in SNO++ Klapdor-Kleingrothaus et al. , Phys. Lett. B 586, 198, (2004) simulation: one year of data maximum likelihood statistical test of the shape to extract 0 n and 2 n components…~240 units of Dc 2 significance after only 1 year!

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

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

Underground Facilities

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

Ladder Labs Wide Drift Electrical, 20’x 12’ AHUs (19’ to back) Wide Drift 25’x 17’ (25’ to back) Access Drift 15’x 10’ (15’ to back) Chemistry Lab SNOLAB Workshop IV, 15 Aug 2005

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

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

Surface Facility SNOLAB Workshop IV, 15 Aug 2005

Experimental Interest in SNOLAB SNO + & SNO ++ Lithium Detector CLEAN Solar Neutrinos & Double Beta Decay Solar Neutrinos & Dark Matter Majorana Double Beta Decay Ger. DA Double Beta Decay EXO Double Beta Decay COBRA Double Beta Decay Super. CDMS Dark Matter ZEPLIN Dark Matter XENON Dark Matter DEAP Dark Matter PICASSO Dark Matter COUPP Dark Matter DRIFT Dark Matter Noble Liquid Tracking Detectors Solar Neutrinos HALO Supernovae Neutrinos LENA Proton Decay, Solar Neutrinos, Supernovae Neutrinos NOSTOS TRIGA Neutrino Oscillations (q 13) Neutron-Antineutron Oscillations

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