1. KamLAND: Disappearance of Reactor Anti-neutrinos
Kam-Biu Luk
University of California, Berkeley
and
Lawrence Berkeley National Laboratory
Neutrino at Daya Bay, 28 Nov 2003

2. Neutrino at Daya Bay, 28 Nov 2003
Determination of Dm122 and q12
LMA is favoured
This region can be
explored with reactor 
with a baseline of ~100 km
~ 100 km
Neutrino at Daya Bay, 28 Nov 2003

3. Neutrino at Daya Bay, 28 Nov 2003
The KamLAND Experiment
Neutrino at Daya Bay, 28 Nov 2003

4. Neutrino at Daya Bay, 28 Nov 2003
Nuclear Reactors in Japan
~80GW
~ 180 km
86% of  events
from ~180 km
Neutrino at Daya Bay, 28 Nov 2003

5. Neutrino at Daya Bay, 28 Nov 2003
Thermal Flux from Japanese Reactors
Neutrino at Daya Bay, 28 Nov 2003

6. Neutrino at Daya Bay, 28 Nov 2003
The KamLAND Detector r m Dr
Present analysis
~22%
(3.2 kton)
Neutrino at Daya Bay, 28 Nov 2003

7. Detecting Reactor ne in Liquid Scintillator
Neutrino at Daya Bay, 28 Nov 2003

8. Neutrino at Daya Bay, 28 Nov 2003
Reconstructing Position
68Ge : MeV (g + g) Zn : MeV (g)
60Co : MeV (g +g) AmBe : 2.20 , 4.40, 7.6 MeV (g)
-5m 5m
Position resolution ~ 25 cm
Neutrino at Daya Bay, 28 Nov 2003

9. Neutrino at Daya Bay, 28 Nov 2003
Energy Determination
DE/E ~ 7.5% /√E , Light Yield ~ 300 p.e./MeV
Energy scale stable to 0.6% through out the period
DEsyst = 1.91% at 2.6 MeV  2.13% for ne
Neutrino at Daya Bay, 28 Nov 2003

10. Neutrino at Daya Bay, 28 Nov 2003
An Anti-neutrino Candidate
Delayed E ~ 2.22 MeV
Prompt E ~ 3.2 MeV m
charge
time
Dt ~ 110 msec
DR ~ 0.35 m
Neutrino at Daya Bay, 28 Nov 2003

11. Neutrino at Daya Bay, 28 Nov 2003
m-Induced Neutrons & Spallation-12B/12N
DL < 3m
12B
12N
Neutrino at Daya Bay, 28 Nov 2003

12. Neutrino at Daya Bay, 28 Nov 2003
R3 Vertex Distributions of Neutrons & 12B/12N
DV/V = 4.06 %
DVfid/Vfid = 4.6 %
Neutron
R = 5m
Neutrino at Daya Bay, 28 Nov 2003

13. Neutrino at Daya Bay, 28 Nov 2003
Radioactivity inside Liquid Scintillator
Neutrino at Daya Bay, 28 Nov 2003

14. Energy Spectrum of Radioactivity inside Liquid Scintillator× 
Requirements for reactor ne detection:
238U 232Th ~ g/g
40K ~ g/g
Neutrino at Daya Bay, 28 Nov 2003

15. Neutrino at Daya Bay, 28 Nov 2003
Estimated Systematic Uncertainties
For Eprompt > 2.6 MeV
4.60 %
Total LS mass 2.13
Fiducial mass ratio 4.06
Energy threshold 2.13
Tagging efficiency 2.06
Live time
Reactor power 2.05
Fuel composition
Time lag
ne spectra
Cross section 0.2
Total Uncertainty %
Neutrino at Daya Bay, 28 Nov 2003

16. Neutrino at Daya Bay, 28 Nov 2003
ne Event Selection
Data Sample
Mar. 4 – Oct. 6, ton•yr (145.1 days)
Fiducial cut:
• R < 5m
Mass = 408 ton, yielding
3.46 x 1031 free protons
Inverse b-decay selection:
• no OD signals
• Eprompt > 2.6 MeV
• 1.8 < Edelay < 2.6 MeV
• DR < 1.6m, 0.5 < DT < 660 msec
Using AmBe & LED, tag= (78.31.6)%
Software cut on Spallation event:
• DTm < 2sec
• DEm > 3 GeV or DRm < 3m
Eprompt > 2.6 MeV
x2 + y2 (m2) 8 6 4 2 -2 -4 -6 -8
Z (m)
Neutrino at Daya Bay, 28 Nov 2003

17. Correlation Between Prompt
and Delayed Energies
g from n12C
Neutrino at Daya Bay, 28 Nov 2003

18. Neutrino at Daya Bay, 28 Nov 2003
First Results From KamLAND
Based on 162 ton•yr, with Eprompt > 2.6 MeV
Final sample, Nobs 54 events
Expected, Nno  5.6(sys) events
Background, Nbg 0.95  0.99 event
Accidental  event
9Li/8He (b, n)  0.85 event
fast neutron < 0.5 event
Evidence for Reactor ne Disappearance
=  (stat)  (sys)
Nobs - Nbg
Nno
Neutrino at Daya Bay, 28 Nov 2003

19. Perspective of Observed Rate Deficit
LMA:
Dm122 = 5.5x10-5eV2
sin2212 = 0.833
G.Fogli et al., PR
D66, ,
(2002)
LMA flux prediction
at 95% C.L.
Nobs/N no_osc
Neutrino at Daya Bay, 28 Nov 2003

20. Neutrino at Daya Bay, 28 Nov 2003
Implication of Observed Rate Deficit
Before
KamLAND
Neutrino at Daya Bay, 28 Nov 2003

21. Neutrino at Daya Bay, 28 Nov 2003
Energy Spectrum (Eprompt > 2.6 MeV)
Neutrino at Daya Bay, 28 Nov 2003

22. Impact of KamLAND Results on
Dm122 and q12
Best fit :
Dm122 = 6.9 x 10-5 eV2
sin22q12 = 1.0
95 % C.L.
Neutrino at Daya Bay, 28 Nov 2003

23. Neutrino at Daya Bay, 28 Nov 2003
Operation of Reactors
2002
Spring 2003 : Inspection
2006
Reduce rate by 50%
but good for studying
backgrounds
Useful for distinguishing
LMA-I from LMA-II
Neutrino at Daya Bay, 28 Nov 2003

24. Neutrino at Daya Bay, 28 Nov 2003
Future Prospects
95 % C.L.
With 5 years of running
Neutrino at Daya Bay, 28 Nov 2003

25. Neutrino at Daya Bay, 28 Nov 2003
Conclusions
Based on 162 ton•yr of data, KamLAND observed
a deficit in the number of ne events.
Interpreting this observation as evidence of neutrino
oscillation, it implies the LMA solution as the most
viable explanation of the solar-neutrino problem.
With higher statistics, we will look for spectral
distortion, and measure neutrino mixing parameters
with better precision.
Neutrino at Daya Bay, 28 Nov 2003

26. Neutrino at Daya Bay, 28 Nov 2003
The KamLAND Collaboration
K.Eguchi, S.Enomoto, K.Furuno, Y.Gando, H.Ikeda, K.Ikeda, K.Inoue, K.Ishihara, T.Iwamoto, T.Kawashima, Y.Kishimoto, M.Koga, Y.Koseki, T.Maeda, T.Mitsui, M.Motoki, K.Nakajima, H.Ogawa, K.Oki, K.Owada, I.Shimizu, J.Shirai, F.Suekane, A.Suzuki, K.Tada, O.Tajima, K.Tamae, H.Watanabe
Tohoku University
L.DeBraeckeleer, C.Gould, H.Karwowski, D.Markoff, J.Messimore, K.Nakamura, R.Rohm, W.Tornow, A.Young
TUNL
J.Busenitz, Z.Djurcic, K.McKinny, D-M.Mei, A.Piepke, E.Yakushev
University of Alabama
P.Gorham, J.Learned, J.Maricic, S.Matsuno, S.Pakvasa
University of Hawaii
B.D.Dieterle
University of New Mexico
M.Batygov, W.Bugg, H.Cohn, Y.Efremenko, Y.Kamyshkov, Y.Nakamura
University of Tennessee
G.A.Horton-Smith, R.D.McKeown, J.Ritter, B.Tipton, P.Vogel
California Institute of Technology
C.E.Lane, T.Miletic
Drexel University
Y-F.Wang
IHEP, Beijing
T.Taniguchi
KEK
B.E.Berger, Y-D.Chan, M.P.Decowski, D.A.Dwyer, S.J.Freedman, Y.Fu, B.K.Fujikawa, J.Goldman,
K.M. Heeger, K.T.Lesko, K-B.Luk, H.Murayama, D.R.Nygren, C.E.Okada, A.W.Poon, H.M.Steiner, L.A.Winslow
UC Berkeley/LBNL
S.Dazeley, S.Hatakeyama, R.C.Svoboda
Louisiana State University
J.Detwiler, G.Gratta, N.Tolich, Y.Uchida
Stanford University
Neutrino at Daya Bay, 28 Nov 2003

27. Neutrino at Daya Bay, 28 Nov 2003
Neutrino Mixing
If neutrinos have mass, it is possible that the weak eigenstates
are not the same as the mass eigenstates:
PMNS (Pontecorvo-Maki-Nakagawa-Sakata) matrix
The time evolution of the flavour eigenstate is then given by:
Neutrino at Daya Bay, 28 Nov 2003

28. Neutrino at Daya Bay, 28 Nov 2003
Evidence of Neutrino Oscillation
Atmospheric  (SuperK)
Solar n (SNO)
Accelerator  (LSND)
Neutrino at Daya Bay, 28 Nov 2003

29. Neutrino at Daya Bay, 28 Nov 2003
Probability of Neutrino Mixing
Parametrize the mixing matrix as:
atmospheric n reactor n @ short baseline solar n
The probability of ne  ne is:
at large L/En.
Neutrino at Daya Bay, 28 Nov 2003