1. The Status of KamLAND After Purification
Christopher Grant
for the KamLAND Collaboration
APS April Meeting 2010
February 14, 2010

2. KamLAND: The Early Days
Ref: Phys. Rev. Lett. 90, (2003)
Reactor and Geo anti-neutrinos via inverse β-decay:
Prompt
(plus annihilation energy)
Delay
(2.2 MeV γ from n-capture)
KamLAND + Solar neutrino data:
LMA-I mixing solution
favored by more than 4σ!
Ref: Phys. Rev. Lett. 100, (2008)
February 14, 2010
APS April Meeting 2010

3. What about solar neutrinos?
Can we test the accuracy of the Standard Solar Model (SSM)?
Solar neutrino detection by elastic scattering:
KamLAND
This talk will focus on the 863 keV - 7Be ν flux
7Be ν flux in KamLAND predicted by SSM: ~500 events/(kton·day)
According to BPS08(GS)
Ref: A. Serenelli (
February 14, 2010
APS April Meeting 2010

4. Backgrounds in KamLAND
Event Distribution as of April 2007
Background after fiducial cuts
Dominant backgrounds at low energies are from naturally occurring radioactive isotopes.
Background is ~105 times greater!!
If we clean up our liquid scintillator, what can we expect to see?
7Be ν signal
February 14, 2010
APS April Meeting 2010

5. Backgrounds in KamLAND
An Ideal Scenario after Purification
Assuming the following reduction factors:
The purification system must be extremely efficient at removing radioactive forms of lead and gaseous isotopes!
Ideal Scenario
Purify by distilling and high-purity N2 purging
7Be ν signal
February 14, 2010
APS April Meeting 2010

6. KamLAND Detector Scintillator Composition: 80.2% Dodecane
Depth of 2700 m.w.e
Scintillator Composition:
Calibration device inside glove box
80.2% Dodecane
19.8% Pseudocumene
1.36 g/l PPO
Chimney region
Stainless Steel vessels
Buffer oil region
(18 meter diameter)
Inner Detector PMTs (17” + 20”)
1-kton of LS
Acrylic vessel for buffer region
Liquid Scintillator Inner Detector
(12 meter diameter)
Outer Water Cerenkov Detector
Kevlar ropes supporting EVOH balloon
Outer Detector PMTs (20”)
February 14, 2010
APS April Meeting 2010

7. Purification System
KamLAND detector can be filled from the top or the bottom
February 14, 2010
APS April Meeting 2010

8. N2 Generator Distillation System Close-up February 14, 2010
APS April Meeting 2010

9. Quality Monitoring Light Attenuation
Measured by β-α coincidence using MiniLAND – A small scale scintillation detector with about 1 mBq/m3 sensitivity
Concentrations of < 10 mBq/m3 were observed
Ref: H. Takahashi (Internal Report, 3/19/2009)
Ref: C. Grant (Internal Report, 1/22/2009)
Light Yield
Estimated by a Residual Gas Analyzer system with about 1 μBq/m3 sensitivity
Concentrations of < 32 μBq/m3 for Kr and < 1 μBq/m3 for Ar were observed
Ref: Y. Minekawa (Internal Report, 1/22/2009)
Ref: C. Zhang (Internal Report, 9/4/2008)
February 14, 2010
APS April Meeting 2010

10. Detector Status Events with Energy: 0.5 MeV < E < 1.0 MeV
Purified LS
Boundary can be seen when filling the detector with purified LS
Old LS
Very important to keep a boundary between purified and old LS during filling!
February 14, 2010
APS April Meeting 2010

11. A Truly Ful-“filling” Cinematic Experience
February 14, 2010
APS April Meeting 2010

12. Purification Summary
Two separate purification campaigns were performed
1st campaign occurred from April 17, 2007 to September 25, 2007
2nd campaign occurred from June 16, 2008 to February 6, 2009
~ 6440 cubic meters of liquid scintillator was distilled throughout both campaigns (~ 5.4 volume transfers!)
Changes in optical properties were noticed during purification which caused a decrease in light yield and transparency
Limiting factor when deciding how long to continue purifying
Separation of old LS and purified LS in the detector was very difficult during 1st campaign, but improved during 2nd campaign
February 14, 2010
APS April Meeting 2010

13. Data After Purification
I have performed a preliminary analysis from 111 days of live-time and 75 m3 of fiducial volume for a total exposure of 6.49 kton·day
Assume no 7Be ν
Now compare χ2 of the “no 7Be ν” assumption to χ2 of fit with 7Be ν
February 14, 2010
APS April Meeting 2010

14. Data After Purification
Δχ2 = 7.2 between fits with and without 7Be ν signal
SSM prediction: ~500 events/(day·kton) - BPS08(GS)
Borexino: 490 ± 30 (stat) ± 40 (sys) events/(kton·day)
Ref: Phys. Rev. Lett., 101, (2008)
There is evidence for a solar signal
February 14, 2010
APS April Meeting 2010

15. Conclusion
After two purification campaigns we have seen incredible reduction factors of:
Preliminary data analysis with 6.49 kton·day exposure shows statistical evidence for a 7Be ν signal from Δχ2 comparison of fits with and without the 7Be ν spectrum
Yet to come...a more detailed analysis having greater exposure!
A separate analysis has estimated that a 13% statistical uncertainty for the 7Be ν flux can be reached with a 73 kton·day exposure
Ref: K. Nakajima, Internal Report, 9/25/2009
February 14, 2010
APS April Meeting 2010

16. The KamLAND Collaboration
The University of Alabama
A. Piepke, C. Grant, G. Keefer
The University of Tennessee
Y. Efremenko
UC Berkeley and LBNL
T. Banks, T. Bloxham, J. Detwiler,
S. Freedman, B. Fujikawa, K. Ichimura,
R. Kadel, T. O'Donnell, H. Steiner
RCNS, Tohoku University, Japan
A. Suzuki, K. Inoue, J. Shirai, M. Koga,
T. Mitsui, K. Nakamura, Y. Kishimoto,
K. Tamae, H. Gando, I. Shimizu,
S. Yoshida, H. Ikeda, Y. Kibe,
K. Nakajima, Y. Shimizu, Y. Minekawa,
Y. Takemoto, A. Terashima, H. Watanabe,
W. Kimura, N. Nagai, H. Takahashi,
T. Morikawa, K. Narita, H. Yabumoto,
H. Yoshida, N. Takhashi, X. Benda
Stanford University
G. Gratta, K. Downum
Caltech University
B. McKweon, D. Dwyer, C. Zhang
Kansas State University
G. Horton-Smith
University of Wisconsin - Madison
K. Heeger
University of Hawaii at Manoa
J. Learned, S. Matsuno
The University of Washington
S. Enomoto
The University of Washington
S. Enomoto
TUNL
H. Karwowski, D. Markoff, W. Tornow
Drexel University
C. Lane, J. Maricic
NIKHEF
P. Decowski
Colorado State University
B. Berger
February 14, 2010
APS April Meeting 2010