neutrino at daya bay, 28 nov 2003 kamland: disappearance of reactor anti-neutrinos kam-biu luk...
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Neutrino at Daya Bay, 28 Nov 2003
KamLAND: Disappearance of Reactor Anti-neutrinos
Kam-Biu Luk
University of California, Berkeleyand
Lawrence Berkeley National Laboratory
Neutrino at Daya Bay, 28 Nov 2003
Determination of m122 and 12
• 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
Nuclear Reactors in Japan
~80GW
~ 180 km
86% of eventsfrom ~180 km
Neutrino at Daya Bay, 28 Nov 2003
68Ge : 1.012 MeV (+) 65Zn : 1.116 MeV ()60Co : 2.506 MeV ( +) AmBe : 2.20 , 4.40, 7.6 MeV
-5m 5m
Reconstructing Position
Position resolution ~ 25 cm
Neutrino at Daya Bay, 28 Nov 2003
Energy Determination
E/E ~ 7.5% /√E , Light Yield ~ 300 p.e./MeVEnergy scale stable to 0.6% through out the period
Esyst = 1.91% at 2.6 MeV 2.13% for e
Neutrino at Daya Bay, 28 Nov 2003
Prompt E ~ 3.2 MeV
t ~ 110 sec
Delayed E ~ 2.22 MeV
R ~ 0.35 m
An Anti-neutrino Candidate
timecharge
Neutrino at Daya Bay, 28 Nov 2003
V/V = 4.06 %
Vfid/Vfid = 4.6 %
Neutron
R = 5m
R = 5m
R3 Vertex Distributions of Neutrons & 12B/12N
Neutrino at Daya Bay, 28 Nov 2003
Energy Spectrum of Radioactivity inside Liquid Scintillator
×
×
×
Requirements for reactor e detection:
238U 232Th ~ 10-14 g/g 40K ~ 10-15 g/g
Neutrino at Daya Bay, 28 Nov 2003
Estimated Systematic Uncertainties
For Eprompt > 2.6 MeV
4.60
%Total LS mass 2.13Fiducial mass ratio 4.06Energy threshold 2.13Tagging efficiency 2.06Live time 0.07Reactor power 2.05Fuel composition 1.00Time lag 0.28e spectra 2.48Cross section 0.2
Total Uncertainty 6.42 %
Neutrino at Daya Bay, 28 Nov 2003
Data Sample Mar. 4 – Oct. 6, 2002 162 ton•yr (145.1 days)
Fiducial cut: • R < 5m Mass = 408 ton, yielding 3.46 x 1031 free protons Inverse -decay selection: • no OD signals • Eprompt > 2.6 MeV • 1.8 < Edelay < 2.6 MeV • R < 1.6m, 0.5 < T < 660 sec Using AmBe & LED, tag= (78.31.6)% Software cut on Spallation event: • T < 2sec
• E > 3 GeV or R< 3m
e Event Selection
Eprompt > 2.6 MeV
x2 + y2 (m2)
8
6
4
2
0
-2
-4
-6
-80 5 10 15 20 25 30 35 40 45 50
Z (m)
Neutrino at Daya Bay, 28 Nov 2003
• Based on 162 ton•yr, with Eprompt > 2.6 MeV
Final sample, Nobs 54 events Expected, Nno 86.8 5.6(sys) events
Background, Nbg 0.95 0.99 event Accidental 0.0086 0.0005 event 9Li/8He (, n) 0.94 0.85 event fast neutron < 0.5 event
• Evidence for Reactor e Disappearance
First Results From KamLAND
= 0.611 0.085 (stat) 0.041 (sys)Nobs - Nbg
Nno
Neutrino at Daya Bay, 28 Nov 2003
Perspective of Observed Rate Deficit
LMA: m12
2 = 5.5x10-5eV2
sin22 = 0.833G.Fogli et al., PR D66, 010001-406,(2002)
LMA flux predictionat 95% C.L.
Nob
s/N
no_
osc
Neutrino at Daya Bay, 28 Nov 2003
Impact of KamLAND Results onm12
2 and 12
Best fit : m12
2 = 6.9 x 10-5 eV2
sin22= 1.0
95 % C.L.
Neutrino at Daya Bay, 28 Nov 2003
Spring 2003 : Inspection 2006
2002
Operation of Reactors
Useful for distinguishingLMA-I from LMA-II
Reduce rate by 50%but good for studyingbackgrounds
Neutrino at Daya Bay, 28 Nov 2003
• Based on 162 ton•yr of data, KamLAND observed a deficit in the number of e 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.
Conclusions
Neutrino at Daya Bay, 28 Nov 2003
G.A.Horton-Smith, R.D.McKeown, J.Ritter, B.Tipton,
P.VogelCalifornia Institute of Technology
C.E.Lane, T.MileticDrexel University
Y-F.WangIHEP, Beijing
T.TaniguchiKEK
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.SvobodaLouisiana State University
J.Detwiler, G.Gratta, N.Tolich, Y.UchidaStanford University
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.WatanabeTohoku University
L.DeBraeckeleer, C.Gould, H.Karwowski, D.Markoff,
J.Messimore, K.Nakamura, R.Rohm, W.Tornow,
A.YoungTUNL
J.Busenitz, Z.Djurcic, K.McKinny, D-M.Mei, A.Piepke,
E.YakushevUniversity of Alabama
P.Gorham, J.Learned, J.Maricic, S.Matsuno,
S.PakvasaUniversity of Hawaii
B.D.Dieterle
University of New Mexico
M.Batygov, W.Bugg, H.Cohn, Y.Efremenko, Y.Kamyshkov, Y.NakamuraUniversity of Tennessee
The KamLAND Collaboration
Neutrino at Daya Bay, 28 Nov 2003
• 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
Neutrino Mixing
e
Ue1 Ue2 Ue3U1 U2 U3
U1 U2 U 3
123
e Ue1e iE1t1 Ue2e
iE2t2 Ue3e iE 3t3
• The time evolution of the flavour eigenstate is then given by:
Neutrino at Daya Bay, 28 Nov 2003
Evidence of Neutrino Oscillation
Accelerator (LSND)Solar (SNO)Atmospheric (SuperK)
Neutrino at Daya Bay, 28 Nov 2003
• Parametrize the mixing matrix as:
• The probability of ee is:
Probability of Neutrino Mixing
U 1 0 0
0 cos23 sin230 sin23 cos23
cos13 0 e i sin130 1 0
e i sin13 0 cos13
cos12 sin12 0
sin12 cos12 0
0 0 1
atmospheric reactor @ short baseline solar
P e e 1 sin2 (212 )sin2m12
2 L
4E
at large L/E.
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