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SNO+ Neutrino Geophysics, Honolulu, Hawaii December 15, 2005 Mark Chen Queen’s University Sudbury Neutrino Observatory 1000 tonnes D2O 12 m diameter Acrylic Vessel 18 m diameter support structure; 9500 PMTs (~60% photocathode coverage) 1700 tonnes inner shielding H2O 5300 tonnes outer shielding H2O Urylon liner radon seal depth: 2092 m (~6010 m.w.e.) ~70 muons/day Depth Matters! SNO Timeline 1998 1999 2000 2001 2002 2003 2004 2005 2006 NOW commissioning Pure D2O Salt 3He added 2 ton of NaCl Counters Pure D2O and desalination • pure D2O phase discovers active solar neutrino flavors that are not ne • 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 8B 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 – 3He proportional counter array • dedicated Neutral Current Detectors (NCDs) • taking production data – data taking end date: 31 Dec 2006 • will bring total uncertainty on 8B solar n NC signal below 5% – physics with heavy water will be complete – heavy water will be returned to AECL in 2007 what should be done next? 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? SNO+ Technical Issues liquid scintillator selection compatibility with acrylic vessel high light yield, long attenuation length reversing the acrylic vessel mechanics SNO: AV contains heavy water, must hold up SNO+: AV contains scintillator, r < 1 g/cm3, must hold down liquid scintillator purification Acrylic Vessel Hold-down • “rope net” being designed to hold down 15% density difference (buoyancy) SNO SNO+ Scintillator Wish List • high density (>0.85 g/cm3) • 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.” • • • • 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, producer has been very accommodating • high purity SNO+ Monte Carlo • light yield simulations KamLAND scintillator in SNO+ 629 ± 25 pe/MeV above no acrylic 711 ± 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 ~300 pe/MeV 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 KamLAND scintillator Light Attenuation Length Petresa LAB as received attenuation length around ~20 m @ 420 nm 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 r = 0.86 g/cm3 acceptable • …default is Petresa LAB with 4 g/L PPO, wavelength shifter 10-50 mg/L bisMSB • because solvent is undiluted and SNO photocathode coverage is high, expect light output (photoelectrons/MeV) ~3× KamLAND Geo-Neutrinos 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 Geo-Neutrino Signal terrestrial antineutrino event rates: • Borexino: 10 events per year (280 tons of C9H12) / 29 events reactor • KamLAND: 29 events per year (1000 tons CH2) / 480 events reactor • SNO+: 64 events per year (1000 tons CH2) / 87 events reactor based on Rothschild, Chen, Calaprice Geophys. Res. Lett. 25, 1083 (1998) KamLAND geo-n in SNO+ SNO+ geo-neutrinos and reactor background KamLAND geo-neutrino detection…July 28, 2005 in Nature fraction of total flux SNO+ geo-neutrino source integral crust: blue mantle: black total: red distance from detector [km] SNO+ Geo-neutrinos a good follow-up to KamLAND’s first detection potential to really constrain the radiogenic heat flow potential for geochemistry (separate measurement of U and Th) simple geological configuration old, stable, thick continental crust surrounds Sudbury smaller uncertainties? Toy Example – Mantle Component 70-30: the 70 component has 10% uncertainty; that’s 7/30 = 0.23 80-20: the 80 component has 5% uncertainty; that’s 4/20 = 0.20 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+ 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 D2O removed scintillator procurement contracts …and on to converting SNO into an operating, multi-purpose, liquid scintillator detector with unique physics capabilities Low Energy Solar Neutrinos • complete our understanding of neutrinos from the Sun pep, CNO, 7Be p-p Solar Fusion Chain p + p 2H + e+ + ne 2H 3He 7Be + p 3He + + 3He 4He + 2 p 3He + 7Li e− 7Li 3He + p 4He + e+ + ne + 4He 7Be + + + ne +p+ p + e− + p 2H + ne 7Be 8B +p CNO Cycle 13 8B + 2 + e+ + n e N+ 12C +p→ 13C + p → 14N + 14N + p → 15O + 15N + p → 12C + 13N → 13C + e+ + ne 15O → 15N + e+ + ne Neutrino-Matter Interaction • best-fit oscillation parameters suggest MSW occurs from Peña-Garay • but we have no direct evidence of MSW – day-night effect not observed – no spectral distortion for 8B n’s • testing the vacuum-matter transition is sensitive to new physics plug in Dm2 = 8 × 10−5 eV2, q = 34° Ne at the centre of the Sun → E is 1-2 MeV vacuum-matter transition New Physics NC non-standard Lagrangian 0.25 • non-standard interactions • MSW is linear in GF and limits from n-scattering experiments g2 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 alsoto Balantekin Yuksel, PRD 68, the “sweetand spot” test forand new physics 013006 (2003) Barger, Huber, Marfatia, hep-ph/0502196 Survival Probability Rise stat + syst + SSM errors estimated SSM pep flux: uncertainty ±1.5% Dm2 = 8.0 × 10−5 eV2 tan2q = 0.45 known source → precision test improves precision on q12 sensitive to new physics: • non-standard interactions • solar density perturbations • mass-varying neutrinos • CPT violation • large q13 • sterile neutrino admixture SNO CC/NC pep n observing the rise confirms MSW and that we know what’s going on 11C Cosmogenic Background these plots from the KamLAND proposal muon rate in KamLAND: 26,000 d−1 compared with SNO: 70 d−1 Event Rates (Oscillated) 7Be resolution with 450 photoelectrons/MeV solar neutrinos 3600 pep/year/kton >0.8 MeV using BS05(OP) and best-fit LMA 2300 CNO/year/kton >0.8 MeV