Transcript Neutrino Oscillations and the Sudbury Neutrino Observatory

Data Processing for the Sudbury
Neutrino Observatory
Aksel Hallin
Queen’s,
October 2006
Sudbury Neutrino
Observatory
Support Structure
for 9500 PMTs,
60% coverage
12 m Diameter
Acrylic Vessel
1700 tonnes Inner
Shielding H2O
5300 tonnes Outer
Shield H2O
Urylon Liner and
Radon Seal
1000 tonnes D2O ($300 M)
Unique Signatures in SNO (D2O)
Charged-Current (CC)
e+d  e-+p+p
Ethresh = 1.4 MeV
e only
Neutral-Current (NC)
x+d  x+n+p
Ethresh = 2.2 MeV
Equally sensitive to e m t
Elastic Scattering (ES)
x+e-  x+ex, but enhanced for e
3 ways to
detect neutrons
Numerical tools for SNO
•
•
•
•
“Data Cleaning”
Monte Carlo
“Fitters”
“Physics Interpretation”
Raw Data: ti , xpmt , qi
Reconstruction
u
x
E
t
Particle ID (14 )
Signal Extraction
CC day d CC d  ES
CC ,  NC ,  ES ,
,
,
CC night dTeff dTeff
Physics interpretation
m , sin 2  ...
2
2
Observables
Photomultiplier tube
-position
-time
-charge
E Lddir

event
xi  Reconstructed
x
ti 
 t0
-vertex
-direction
win ( , c
n
Pdir (i , i , fit ,  fit N)
i i i , rfit ,  fit ,  fit )
-energy
 pmt ( )
( m d  m d  m d )
 hardware drift  2  N 21 N g ( ,  )e 1
RP(r ,  ,  ,  ) M (-isotropy
r ,  ,  )



 
cos


9

20cos
2


35cos
4




1 1
14
N ( N  1)

i 1 j i 1
ij
64
2 2
3 3
ij
ij

“Data Cleaning”
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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
450188649
Neutrino triggers (hit multiplicity)
191312560
Analysis Nhit cut (Nhit > 21)
10088842
Low-level cuts
7805238
`Cherenkov Box' cuts
3418439
Fiducial volume cut
67343
Energy threshold (Te > 5 MeV)
3440
Muon follower cut
2981
Atmospheric followers
2928
Total candidates
2928
Extracting the Solar  Flux
CC
NC
• PDFs: kinetic energy T, event
location R3, solar angle
correlation cos sun
ES
Maximum
Likelihood Fit
 CC  NC  ES
OR
 e mt

Assumption:
No 8B shape distortion

shape constrained fit:
[in 106 cm-2 s-1]
8B
No
8B
constrained
SNO
 5.09
0.44
0.46
(stat.)
(syst.)
0.43
0.43
1.57
0.55
unconstrained


6.42
(stat.)
(syst.)
shape constraint: SNO
1.57
0.58
3 Phases of SNO: neutron (NC) detection
methods (systematically different)
Phase I (D2O)
Nov. 99 - May 01
Phase II (salt)
July 01 - Sep. 03
n captures on
2H(n, g)3H
Effc. ~14.4%
NC and CC separation
by energy, radial, and
directional
distributions
2 t NaCl. n captures on
35Cl(n, g)36Cl
Effc. ~40%
NC and CC separation
by event isotropy
35Cl+n
2H+n
Phase III (3He)
Nov. 04-Dec. 06
40 proportional
counters
3He(n, p)3H
Effc. ~ 30% capture
Measure NC rate with
entirely different
detection system.
5 cm
8.6 MeV
n
6.25 MeV
3H
p
3He
3H
n + 3He  p + 3H
36Cl
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 1/05
Dec 1/05
RUN TYPE
# OF DAYS
PERCENTAGE
========================================
NEUTRINO
249.58
68.19
SUPERNOVA
0.14
0.04
CALIBRATION
89.26
24.39
OTHER
14.47
3.95
NO RUN
12.55
3.43
Calibration Source Manipulator
Umbilicals
Manipulation
Detector Interface
Radon/Light Barrier
Accuracy
< 2 cm single axis
~ 5 cm triple axis
Remote Operation/Interlocks
Stringent Cleanliness Requirements
337,365,386,
420,500,620
nm
wavelengths
45 Hz Pulse
rate
Intensity
dynamic
range about
1e7
600 ps pulse
width
Optical Analysis
N ij  N i ij RijTij Lij  j e
  d d  d  d a a  d h h 
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”
Oij 
Ni ij RijTij Lij
Nooj RojToj Loj
Typically 40 runs x 7000 pmts = 280,000 data points
Fit for about 400 parameters:
Ni , R( ), L( ,  ), d , h ,  a
e
 d  d  a a  h h 
Optical Analysis
D2O Attenuation
H2O Attenuation
PMT calibrations, PMT angular response, D20, acrylic,H2O
PMT Angular Response
Swapped pmts- angle of rotation