Results (and Expectations) from SNO, the Sudbury Neutrino Observatory Richard L. Hahn PRC-US...
-
Upload
june-ellis -
Category
Documents
-
view
218 -
download
0
Transcript of Results (and Expectations) from SNO, the Sudbury Neutrino Observatory Richard L. Hahn PRC-US...
Results (and Expectations) from SNO, the Sudbury Neutrino Observatory
Richard L. Hahn
PRC-US WorkshopBeijing, June 2006
*Research sponsored by the Office of Nuclear Physics, Office of Science, U.S. Department of Energy
Solar-Neutrino & Nuclear-Chemistry Group * Chemistry Department, BNL
Brookhaven Science AssociatesU.S. Department of Energy
Predicted Energy Spectra of Solar Neutrinos
from the Standard Solar Model (SSM)
Arrows Denote ExperimentalThresholds
71Ga 37Cl Water
LENS
Super-K, SNOSNO+
• Done:Done: HOMESTAKEHOMESTAKE Radiochemical Detector
C2Cl4; 37Cl + e 37Ar + e- (~40 years)
• Done:Done: GALLEX GALLEX Radiochemical Detector
Ga; 71Ga + e 71Ge + e- (1986 - 1998)
• NowNow:: SNO SNO Water Čerenkov Real-time Detector
Ultra-pure D2O (1996 - 2006) • New : #1 Focus for the FutureNew : #1 Focus for the Future THETA-13 THETA-13 High-Precision Experiments
at Daya Bay Nuclear Reactors Real-time Detector (R&D)
Gd in Liquid Scintillator, Gd-LS (began 2004)
• NewNew: : LENS LENS Real-time Detector (R&D) 115In-LS (began 2000), Detect pp and 7Be Solar Neutrinos• New:New: Very Long-Baseline Neutrino Oscillations Very Long-Baseline Neutrino Oscillations
Neutrino Beam from Accelerator (R&D began 2002)• New:New: SNOLab, SNO+ SNOLab, SNO+ (R&D) with LS (began 2005)
>40 Years of Neutrino R&D @ BNL Chemistry Dep’t.
Note: Hahn became Leader of BNL Group in 1986: GALLEX, SNO, 13
hBrookhaven Science AssociatesU.S. Department of Energy
BNL’s Ray Davis and His Discoveries
He was the first to observe neutrinos from the Sun. This was a very significant result, confirming our ideas of how stars produce energy. This was the basis of his 2002 Nobel Physics Prize. But, in a sense, we scientists expected that result. More exciting for us, he observed an unexpected result, too few neutrinos compared to the SSM. This anomaly became known as the Solar Neutrino Problem, and led to several important experiments; some were done by the BNL Solar-Neutrino Group. Ray Davis died May 31, 2006, at age 91+.Ray Davis died May 31, 2006, at age 91+.
Solar Neutrino Problem-”Disappearance”
PRE-SNO: Either
Solar Models are Incomplete and/or Incorrect, e.g., temperature of core is lower than expected,
OrNeutrinos undergo Flavor
Changing Oscillations (or other “New Physics”).
SOLAR FUSION: 4p 4He + 2e+ + 2e + 26 MeV
Kamiokande
Matter Enhanced Oscillations
SAGE & GALLEX
Homestake
LMA
LOW
SMA
MSW gives a dramatic extension of oscillation sensitivity to potential regions in m2
Solar data are consistent with the MSW hypothesis.
But prior to SNO, only had circumstantial evidence from Cl, Ga, Kamiokande, S-K; i.e.,
we knew thee disappeared.
• Needed definitive proof:
* Appearance measurement
* Independent of SSM
Enter The SNO CollaborationS.D. Biller, M.G. Bowler, B.T. Cleveland, G. Doucas,
J.A. Dunmore, H. Fergani, K. Frame, N.A. Jelley, S. Majerus, G. McGregor, S.J.M. Peeters, C.J. Sims, M. Thorman, H. Wan Chan Tseung, N. West, J.R. Wilson, K. Zuber
Oxford University
E.W. Beier, M. Dunford, W.J. Heintzelman, C.C.M. Kyba, N. McCauley, V.L. Rusu, R. Van Berg
University of Pennsylvania
S.N. Ahmed, M. Chen, F.A. Duncan, E.D. Earle, B.G. Fulsom,H.C. Evans, G.T. Ewan, K. Graham, A.L. Hallin, W.B. Handler,
P.J. Harvey, M.S. Kos, A.V. Krumins, J.R. Leslie, R. MacLellan, H.B. Mak, J. Maneira, A.B. McDonald, B.A. Moffat,
A.J. Noble, C.V. Ouellet, B.C. Robertson, P. Skensved, M. Thomas, Y.Takeuchi
Queen’s University
D.L. WarkRutherford Laboratory and University of Sussex
R.L. HelmerTRIUMF
A.E. Anthony, J.C. Hall, J.R. KleinUniversity of Texas at Austin
T.V. Bullard, G.A. Cox, P.J. Doe, C.A. Duba, J.A. Formaggio, N. Gagnon, R. Hazama, M.A. Howe, S. McGee,
K.K.S. Miknaitis, N.S. Oblath, J.L. Orrell, R.G.H. Robertson, M.W.E. Smith, L.C. Stonehill, B.L. Wall, J.F. Wilkerson
University of Washington
T. Kutter, C.W. Nally, S.M. Oser, C.E. WalthamUniversity of British Columbia
J. Boger, R.L. Hahn, R. Lange, M. YehBrookhaven National Laboratory
A.Bellerive, X. Dai, F. Dalnoki-Veress, R.S. Dosanjh, D.R. Grant, C.K. Hargrove, R.J. Hemingway, I. Levine, C. Mifflin, E. Rollin,
O. Simard, D. Sinclair, N. Starinsky, G. Tesic, D. WallerCarleton University
P. Jagam, H. Labranche, J. Law, I.T. Lawson, B.G. Nickel, R.W. Ollerhead, J.J. Simpson
University of Guelph
J. Farine, F. Fleurot, E.D. Hallman, S. Luoma, M.H. Schwendener, R. Tafirout, C.J. Virtue
Laurentian University
Y.D. Chan, X. Chen, K.M. Heeger, K.T. Lesko, A.D. Marino, E.B. Norman, C.E. Okada, A.W.P. Poon,
S.S.E. Rosendahl, R.G. StokstadLawrence Berkeley National Laboratory
M.G. Boulay, T.J. Bowles, S.J. Brice, M.R. Dragowsky, S.R. Elliott, M.M. Fowler, A.S. Hamer, J. Heise, A. Hime,
G.G. Miller, R.G. Van de Water, J.B. Wilhelmy, J.M. WoutersLos Alamos National Laboratory
Sudbury Neutrino Observatory, SNO
1700 tonnes InnerShielding H2O
1000 tonnes D2O
5300 tonnes Outer Shield H2O
12 m Diameter Acrylic Vessel
5-cm thick walls
Support Structure for 9500 PMTs, 60% coverage
Urylon Liner andRadon Seal
REAL
TIME
One million pieces transported down in the 10 foot square minecage and re-assembled underultra-clean conditions.
Brookhaven Science AssociatesU.S. Department of Energy
10
Reactions in SNO
NCxx
npd
ES -- ee xx
-Low Statistics -Mainly sensitive to e,, some
-sensitivity to and -Strong direction sensitivity
-Gives e energy spectrum well-Weak direction sensitivity 1-1/3cos()- e only.
-Measure total 8B flux from the sun.- Equal cross section for all types
CC-epd e p
Unique Feature: ‘Appearance’ of x vs. ‘Disappearance’ of e
Sensitive to 8B
Phase II (salt)July 01 - Sep. 03
Published
Phase III (3He)Summer 04 - Dec. 06
In Progress
Phase I (D2O)Nov. 99 - May 01
Published
SNO – used 3 neutron detection methods( 3 “different detectors” with possibly different systematics)
n captures on2H(n, )3H
= 0.0005 bObserve 6.25 MeV PMT array readout
Good CC
36 proportional counters3He(n, p)3H = 5330 b
Observe p and 3HPMT-independent
readout, event by event
2 t NaCl. n captures on35Cl(n, )36Cl
= 44 bObserve multiple ’sPMT array readout
Enhanced NC
36Cl
35Cl+n 8.6 MeV
3H
2H+n 6.25 MeV
n + 3He p + 3H
p3H
5 cm
n
3He
One raySeveral rays
X 1/3X 0.45
Signals in SNO (Monte Carlo, Renormalized)
~ 9 NHIT/MEV
Pure D2O Plus Salt
NC Salt (BP98)
Phase 2, NaCl:
Improved NC
Signal, 2003
Results
Phase 1, D2O:
2002 NC Results
SNO Energy Calibrations
’s from 8Li ’s from 16N and t(p,)4He
252Cf neutronsn d t … e
(E = 6.3 MeV)
6.13 MeV
19.8 MeV
Chemistry in SNOChemistry in SNO• Purify the water with respect to radioactivity and non-
radioactive chemical impurities.
• Ion Exchange & Ultrafiltration, MnOx, HTiO, Vacuum & Membrane De-gassing, Reverse Osmosis.
• Assay the water for residual contamination: Need to sample 100’s of tonnes in time period short compared to radioactive decay under study to reach sensitivity.
• Optical clarity.
• Biological Growth.
• Add or remove salt (Phase II).
• Maintain stability of water system: temperature, pressure,...
• Control D2O inventory and ratio of H2O/ D2O.
An important enemy, 232Th Decay Chain…..
s and s interfere with our signals at low energies
’s over 2.2 MeVfrom 208Tl d + n + p
Require 232Th content
< 3.7 x 10-15 g/g in D2O
Measure U/Th Backgrounds in D2O
• In-situ:– Low energy data
via Tl & Bi isotropy
• Ex-situ:– Ion exchange
(224Ra, 226Ra)
– Membrane degassing
– Count daughter product decays
SaltPhase
Several ’s in U and Th chains will photodisintegrate deuteron
Radon Calibration
Energy Spectra Extracted from Salt DataWithout Imposing known 8B Shape
Electron kinetic energy
Flux Values
(Updated 2006)
(106 cm-2 s-1)
CC: 1.68(10)
ES: 2.35(27)
NC: 4.94(43)
Brookhaven Science AssociatesU.S. Department of Energy
Spectral Shapes are Extracted from the Salt Data, Not Assumed to Fit 8B
Shape Difference in CC Flux Between Unconstrained and 8B-Shape Constraint = 0.11 0.05(stat) +0.06
-0.09(syst)(units are 106 cm-2 s-1) Consistent with Hypothesis of No Spectral Distortion CC / NC = 0.306 0.026 (stat) 0.024 (syst) -e / total 1/3, -, / total 2/3 Result is independent of the solar model Results from Salt Phase, LMA Is Favored m2 = 7.1 X 10-5 ev2, 12 = 32.5o
SNO Results from Pure D2OSNO RESULTS, Salt + D2O391 live days
SNO SOLVED THE SOLAR NEUTRINO PROBLEM
SNO CC Result agreeswith Davis’Cl value.
Results from Other Exp’ts.
Measuring Neutrino Oscillation Parameters,Narrowing the Available Phase Space
Solar Neutrinos
Solar Neutrinos+ KamLAND 2003(e rate)
Agreement between oscillation parameters for and
Solar Neutrinos+ KamLAND 2004(e rate+spectrum)
‘Discovery Era in Neutrino Physics Is Finished, Entering Precision Era’
Solar (SNO)
e ,
Atmospheric (Super-K)
Reactor (KamLAND)
Accelerator (K2K)
• Neutrinos oscillate, must have mass
• Evidence for neutrino flavor conversion e
• SNO Solved Solar Neutrino Problem
H2O
D2OLS
m221 =7.8 10-5 eV2
12 =32
m232 =2.410-3 eV2
23 45
13 value UNKNOWN.From CHOOZ, only have limit, < 11° WHY SO SMALL?Want to measure with 1% precision.
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.
Detection Principle
2H + x p + n + x - 2.22 MeV (NC)
3He + n p + 3H + 0.76 MeV
x
n
40 Strings on 1-m grid
440 m total active length
NCD
PMT
SNO Phase III (NCD Phase)- Began 2004, To Finish End of 2006
3He Proportional Counters (“NC Detectors”)
Neutron Capture in the NCDs
~ 1200 n captures per year from solar
n + 3He p + 3H (Q = 764 keV)
p
3H
191 keV
573 keV 764 keV
3H
p
NCD wall
anode wire
Idealized energy spectrum in a 3He proportional counter. The main peak corresponds to the 764-keV Q-value of the 3He(n, p)3H reaction.
End view of an NCD with representative ionization tracks
p hits wall
3H hits wall
p-t track fully contained in gas
NCD Energy Spectrum
191-keV shoulder from proton going into the wall
764-keV peakEnergy spectrum from one deployed NCD string with an Am-Be neutron source.
Other Recent Work from SNO
Are analyzing NCD data (blind analysis) Are analyzing data on atmospheric muons and neutrinos Set new limit on hep flux, to be released very soon SNO is involved in SNEWS Published Periodicity Analysis of SNO data
- Did unbinned log likelihood analysis - No unknown solar period seen- Ruled out at 3.6 level the positive claim by
Sturrock et al. from their Super-K data analysis- Only variation that was seen was due to eccentricity of Earth’s orbit, measured = 0.0143 0.0086
Brookhaven Science AssociatesU.S. Department of Energy
THE FUTURE OF SNO
SNO finished Phase I, with Pure D2O, and Phase II, with NaCl + D2O; now running NCDs for ~2 years. Will end beginning of January 2007. All analyses done blind. New UG facility, “SNO Lab” is funded, being built. Are planning a relatively low-cost new experiment, “SNO+”, to use the existing SNO acrylic vessel, DAQ,and infrastructure; remove the D2O, refill with LS. Goal of SNO+ is to detect low-energy solar from pep and CNO solar branches; see Borexino, LENS… Want to see transition from matter-dominated to vacuum oscillations.