330 likes | 436 Views
Current Status of SNO. Kevin Graham Queen’s University. CAP 2004 Winnipeg. Neutrinos: simple particles. No charge - no mass - only weak interactions g Missing for most experiments. Well…Not Really What do we want to know and how?. Long Baseline Short Baseline Off-axis Atmospheric
E N D
Current Status of SNO Kevin Graham Queen’s University CAP 2004 Winnipeg
Neutrinos: simple particles No charge - no mass - only weak interactions g Missing for most experiments
Well…Not ReallyWhat do we want to know and how? • Long Baseline • Short Baseline • Off-axis • Atmospheric • Solar • Reactor • Double Beta Decay • Supernova • Verify flavour change • Oscillation Signal • Measure mass splittings/hierarchy • Mixing angles • How many types? • Sterile? • Majorana? • Measure individual mass eigenstates • CP violation? • Magnetic moment? Solar measuring q12, Dm12
If neutrinos have mass: Using the oscillation framework: For three neutrinos: Maki-Nakagawa-Sakata-Pontecorvo matrix (Double b decay only) ? ? ? Solar,Reactor Atmospheric CP Violating Phase Reactor... Majorana Phases Range defined for Dm12, Dm23 For two neutrino oscillation in a vacuum: (valid approximation in many cases)
SNO Physics Program • Solar Neutrinos • Electron Neutrino Flux • Total Neutrino Flux • Electron Neutrino Energy Spectrum • Day/Night effects • Seasonal variations • Periodicity • hep neutrinos • Atmospheric Neutrinos & Muons • Downward going cosmic muon flux • Upward going muons and angular dependence • Supernova Watch • Antineutrinos • Nucleon decay (“Invisible” Modes: N nnn) Focus for this talk
Experimental Results SAGE+GALLEX/GNO Flux = 0.58 SSM Homestake Flux = 0.33 SSM Kamiokande+Superkamiokande Flux = 0.46 SSM SNO (CC 0.35) Flux = 1 SSM F = 6.6 × 1010 cm-2 sec-1 Solar Neutrinos
The SNO Detector 9438 Inward- Looking PMTs 2039 m to surface 91 Outward Looking PMTs (Veto) 12 m diameter Acrylic vessel Norite Rock PMT Support Structure (PSUP) 5300 tonnes light water 1000 tonnes heavy water 1700 tonnes light water
n + + + n NC d p n x x Neutrino Reactions in SNO n + + + CC d p p e− e • Q = 1.445 MeV • good measurement of ne energy spectrum • some directional info (1 – 1/3 cosq) • ne only • Q = 2.22 MeV • measures total 8B n flux from the Sun • equal cross section for all n types + + n e− n e− ES x x • low statistics • mainly sensitive to ne, some n and n • strong directional sensitivity
Spectrum Holanda, Smirnov Hep-ph 0212270 5% CC/NC Contours Day – Night Contours (%)
SNO Data Taking Phases Phase II (salty D2O): 254.2 (~400) days Te > 5.5 MeV R < 550 cm 3055 events (~4700) n capture on Cl Multiple g’s 8.6 MeV High CC-NC corr. Te unconstrained Phase III (3He n counters): n capture on 3He n + 3He g p + t Channels indep. gno correlation Reduced NC systematics Phase I (pure D2O): 306.4 live days Te > 5 MeV R < 550 cm 2928 events n capture on D Single 6.25 MeV g High CC-NC corr. Te constrained Counters in Publishing soon Past Present Future
What We Measure PMT Measurements • position • charge • time Reconstructed Event -event vertex -event direction -energy -isotropy
Detector Calibration Optics Energy Event Reconstruction Neutron Capture Backgrounds Tools Pulsed Laser 337nm to 620 nm 16N 6.13 MeV g’s 3H(p,g)4He 19.8 MeV g’s 8Li <13.0 MeV b’s 252Cf neutrons U/Th 214Bi & 208Tl b-g’s Monte Carlo
Pure D2O phase Optical Measurements from Laserball • Optical Constants • alaser at 6 wavelengths • ascan through detector • D2O Attenuation • H2O+AV attenuation • PMT Angular Response • Rayleigh Scattering Salt phase • Calibration used for • MC simulation • Energy calibration • Check systematics
Energy Calibration 16N at centre of detector refelections Data MC s=1.46 ns • Timing Cut • Prompt Time • 20 ns time window • reduce noise/model uncertainties • Energy Calibration • Detector State Corrections • Optical Correction to Centre • DatagMC 16N to set scale
Energy Calibration • generate MC electrons • energies from 2-30 MeV • create ‘look-up’ table NhitsgEnergy • resolution function Resolution Function Nhit/MeVTable sE =A + B(TE)0.5 + C TE
Energy Systematics Sources Include: Detector State Stability a16N centre Optical Model Radial/Asymmetry Timing MC model Total Uncertainty ~1%
g n 36Cl* 36Cl 35Cl Neutrons in Salt g NaCl Capture • Higher capture cross section • Higher energy release • Many gammas s = 44 b 35Cl+n s = 0.0005 b 8.6 MeV 2H+n 6.0 MeV 3H 36Cl
Neutron Capture Efficiency in SNO 35Cl(n,g)36Cl Average Eff. = 0.399 Te≥ 5.5 MeV and Rg ≤ 550 cm 2H(n,g)3H Average Eff. = 0.144 Te≥ 5.0 MeV and Rg ≤ 550 cm Total Systematic Uncertainty ~3%
Cerenkov Light and Isotropy Legendre Polynomials Use: b14 = b1 + 4b4 Systematic Uncertainty ~1% Use for Signal Extraction Charged particle, v > c/n qik 1cone qij >1cone
D2O Radioactivity Assays Controlled radon spike • Radon assay collection points • Top of AV • 2/3 up • Bottom of AV • Radium Assay techniques • MnOx • HTiO <1 n/day bkg
SignalBkg } CC NC ES Fe Fmt Cerenkov Photodis. FitFix Perturb Shift Variables PDF’s Signal Extraction Unconstrained NC E higher Less Rad. Sep. Variables: E, R3, cosqsun, b14 8B Shape Constrained Energy R3 qij cosqsun b14 Extended ML Fit aFluxes aSystematic Uncertainties Directionality Unchanged Isotropy Separation
Measured distributions Measure External n background Position Kinetic Energy Direction Isotropy
Results from Phase I & II CC 1339.6 #EVENTS +69.8 +63.8 +23.9 +20.1 +69.0 +61.5 NC 1344.2 ES 170.3 3055 candidate events 254 live days a 8B shape constrained 8B shape unconstrained Pure D2O (phase I) Salt (phase II)
Global analysis of solar and reactor neutrino data --90% --95% --99% --99.73% LMA I allowed only at 99.73% c.l. Maximal mixing rejected at 5.4 s
SNO Phase III (NCD Phase) Underway x n • 3He Proportional Counters (“NC Detectors”) 40 Strings on 1-m grid 440 m total active length Detection Principle 2H + x p + n + x - 2.22 MeV (NC) 3He + n p + 3H + 0.76 MeV PMT Physics Motivation Event-by-event separation. Measure NC and CC in separate data streams. Different systematic uncertainties than neutron capture on NaCl. NCD array removes neutrons from CC, calibrates remainder. CC spectral shape. NCD
5 cm Cu anode wire (50 m) 3He-CF4 gas mix Length of NCD Strings: 911 m Fused silica insulator CVD nickel counter body (0.36 mm thick) Delay line termination Vectran braid Acrylic ROV ball Acrylic anchor ball NCD Design and Response 3He + n p + 3H + 0.76 MeV
Why Event-by-Event? cc/nc correlation ~ -50% ~0
Summary Pure D2O Phase: Flavour Transformation Neutrinos Massive SSM working well Salt: Increased NC statistics Additional Isotropy Separation Precision Fluxes with No Shape Constraint Improved CC/NC Measurement gFull Salt Data Set (another ~140 days) gDay/Night - Spectral Shape – Eccentricity gImproved oscillation parameter precision Next Phase:NCDs going in (3He counters) event-by-event separation Improved systematics No CC-NC correlation Global Results: g LMA Favoured Global Results: Lower LMA Region Not Maximal Mixing