Data Processing for the Sudbury Neutrino Observatory Aksel Hallin Queen’s, October 2006

Sudbury Neutrino Observatory 1700 tonnes Inner Shielding H 2 O 1000 tonnes D 2 O ($300 M) 5300 tonnes Outer Shield H 2 O 12 m Diameter Acrylic Vessel Support Structure for 9500 PMTs, 60% coverage Urylon Liner and Radon Seal

Unique Signatures in SNO (D 2 O) Charged-Current (CC) e +d  e - +p+p E thresh = 1.4 MeV e only e only Elastic Scattering (ES) x +e -  x +e - x, but enhanced for e Neutral-Current (NC) x + d  x + n+p E thresh = 2.2 MeV Equally sensitive to e   3 ways to detect neutrons

Numerical tools for SNO “Data Cleaning” Monte Carlo “Fitters” “Physics Interpretation”

Signal Extraction Reconstruction Physics interpretation

Observables -position -time -charge Reconstructed event -vertex -direction -energy -isotropy Photomultiplier tube

“Data Cleaning” TABLE II: Number of events remaining in data set after each step in the data processing described in Section 5.. Data Processing Step Events Remaining Total event triggers Neutrino triggers (hit multiplicity) Analysis Nhit cut (Nhit > 21) Low-level cuts `Cherenkov Box' cuts Fiducial volume cut Energy threshold (Te > 5 MeV) 3440 Muon follower cut 2981 Atmospheric followers 2928 Total candidates 2928

Extracting the Solar Flux Maximum Likelihood Fit OR CC NCES PDFs: kinetic energy T, event location R 3, solar angle correlation cos  sun 8 B  shape constrained fit: [in 10 6 cm -2 s -1 ] No 8 B  shape constraint: Assumption: No 8 B shape distortion

Phase II (salt) July 01 - Sep. 03 Phase III ( 3 He) Nov. 04-Dec. 06 Phase I (D 2 O) Nov May 01 3 Phases of SNO: neutron (NC) detection methods (systematically different) n captures on 2 H(n,  ) 3 H Effc. ~14.4% NC and CC separation by energy, radial, and directional distributions 40 proportional counters 3 He(n, p) 3 H Effc. ~ 30% capture Measure NC rate with entirely different detection system. 2 t NaCl. n captures on 35 Cl(n,  ) 36 Cl Effc. ~40% NC and CC separation by event isotropy 36 Cl 35 Cl+n 8.6 MeV 3H3H 2 H+n 6.25 MeV n + 3 He  p + 3 H p 3H3H 5 cm n 3 He

What does it mean to calibrate? Determine unknown parameters in the Monte Carlo. In SNO, these are almost all optical constants. Measure how well we reconstruct position, direction, energy, isotropy as a function of position in the detector and calendar time. In SNO, the calibration effort dominates the analysis. Typically 90% of the analysis effort is used to calibrate, measure backgrounds, and understand systematics; the signal extraction is quite standard. Improvements in the analysis come about because of improved calibration.

SNO Detector Livetime Phase III Livetime: Nov 27, 2004 to Nov 28, 2005 Dec 1/05 Mar 1/05 Jun 1/05 Sep 1/05Dec 1/05 RUN TYPE # OF DAYS PERCENTAGE ======================================== NEUTRINO SUPERNOVA CALIBRATION OTHER NO RUN

Calibration Source Manipulator Radon/Light Barrier Accuracy < 2 cm single axis ~ 5 cm triple axis Remote Operation/Interlocks Stringent Cleanliness Requirements UmbilicalsManipulationDetector Interface

337,365,386, 420,500,620 nm wavelengths 45 Hz Pulse rate Intensity dynamic range about 1e7 600 ps pulse width

Optical Analysis Number of in-time hits in run i and pmt j = (Number of photons emitted in run i) x (solid angle of pmt j and run i) x (pmt angular response) x (transmssion through acrylic) x (laserball intensity distribution) x (efficiency of pmt j) x (transmission through water and acrylic) Remove unknown individual PMT efficiencies with “occratio” Typically 40 runs x 7000 pmts = 280,000 data points Fit for about 400 parameters:

Optical Analysis D 2 O AttenuationH 2 O Attenuation PMT calibrations, PMT angular response, D20, acrylic, H2O

PMT Angular Response

Swapped pmts- angle of rotation