Recent results of KamLAND
Hiroshi Ogawa
Tohoku University
11/28,2003
14th Neutrino Workshop

Contents• KamLAND detector• Reactor neutrino observation• Search for electron anti-neutrino from thesun• Future plan

KamLAND : Kamioka Liquid scintillator Anti-Neutrino Detector

Physics Motivation
Reactor electron anti-neutrinos
Geo electron anti-neutrinos
Solar anti-neutrinos
7Be solar neutrinos
Other anti-neutrino sources
SN neutrinos
Relic neutrinos
KamLAND advantage:high energy resolution
low threshold ~0.9MeV~0.3MeV (in the future)
low background condition

KamLAND Collaboration•Tohoku University: K.Eguch, S.Enomoto, K.Furuno, J.Goldman, H.Hanada, H.Ikeda, K.Ikeda, K.Inoue, K.Ishihara, W.Itoh, T.Iwamoto,T.Kawaguchi, T.Kawashima, H.Kinoshita, Y.Kishimoto, M.Koga, Y.Koseki, T.Maeda, T.Mitsui, M.Motoki, K.Nakajima, M.Nakajima, T.Nakajima,H.Ogawa, T.Sakabe, I.Shimizu, J.Shirai, F.Suekane, A.Suzuki, K.Tada, O.Tajima, T.Takayama, K.Tamae,H.Watanabe•University of Alabama: J.Busenitz, Z.Djurcic, K.McKinny, D-M.Mei, A.Piepke, E.Yakushev•LBNL Berkeley: B.E.Berger, Y.D.Chan, M.P.Decowski, D.A.Dwyer, S.J.Freedman, Y.Fu, B.Fujikawa, 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•California Institute of Technology: G.A.Horton-Smith, R.D.McKeown, J.Ritter, B.Tipton, P.Vogel•Drexel University: C.E.Lane, T.Miletic•University of Hawai Manoa: P.W.Gorham, G.Guilian, J.G.Leanned, J.Maricic, S.Matsuno, S.Pakvasa•Louisiana State University: S.Dazeley, S.Hatakeyama, M.Murakami, R.C.Svoboda•University of New Mexico: B.D.Dieterle, M.DiMauro•Stanford University: J.Detwieler, G.Gratta, K.Ishii, N.Tolich, Y.Uchida•University of Tennessee: M.Batygov, W.Bugg, H.Cohn, Y.Efremenko, Y.Kamyshkov, A.Kozlov, Y.Nakamura•TUNL/ NCSU: L.De Braeckeleer, C.R.Gould, H.J.Karwowski, D.M.Markoff, J.A.Messimore, K.Nakamura, R.M.Rohm, W.Tornow, A.R.Young•IHEP Beijing: Y-F.Wang

KamLAND Collaboration

KamLAND experiment• KamLANDDetector
１０００ｍLS
80% dodecane
20% pseudocumene(1,2,4 Trimethylbenzene)
1.52g/l PPO(2,5-Diphenyloxazole)

1325 17” photo-tubes
22% photo-coverage
1200m3 LSρ = 0.78g/cm3
8,000 photons/MeV
λ ~ 10mBO
50% dodecane
50% isoparaffinρ LS / ρBO = 1.0004

1800m3
Buffer Oil

Water Cherenkov
Outer Detector• νe detection in liquid scintillator

z prompt part : e+Evis = Eνe - ( ∆mnp + me ) - Tn(θ) + 2me= Eνe – 0.782MeV - Tn(θ)
z delayed part : γ (2.2MeV)

Reduce the background
Powerfully !

• The Front-end Electronics

• Vertex Distribution

thermometer• Liquid Scintillator Impurity

µBiPoBiPoµsµsµµ• Cosmic ray muon• Spallation events after muon
BG of neutrino event
9Li & 8He
energy calibration
p capture (2.224MeV)
12C capture (4.947MeV)
12B beta decay
vertex calibration
p capture
12B beta decay(99.5%)(0.5%)

Isotopes

T1/2

Emax (KeV)

12B

20.2 ms

13369(β-)

12N11.0 ms

17338(β+)

11Li

8.5 ms20610(β-)

12B & 12N

9Li

173.8 ms13606(β- n)

9C, 9Li & 8He

8He

119.0 ms

10653(β- n)9C126.6 ms

16498(β+)

8Li838.0 ms

16006(β-)

6He806.7 ms

3508(β-)8B

770.0 ms

17979(β-)

Time dist. after muon
E > 4 MeV

8B & 8Li

Reactor neutrino observation

• Past reactor experimentz

Many different experiments- Baselines up to 1km- No evidence for ν disappearance
More than 100km baseline
is necessary to explore
the LMA solution

Powerful reactor,Big detector,Deep underground• Kamioka location

• Event selection

• Systematic errors• Reactor neutrino analysis result
4 Mar. – 6 Oct. 2002 145.1 live days ( 162 ton-year exposure)
Analysis threshold
Expected signal
BG
Observed

2.6MeV
86.8±5.6
1±154
neutrino disappearance 99.95C.L.
R=0.611±0.085(stat)±0.041(sys)0.9MeV
124.8±7.5
2.9±1.1(+9 geo neutrino)
86LMA
SMA
LOWAssuming CPT invariance :exclude except LMA
exclude RSFP solution too.

VAC• FuturezAnalysis data update : seasonal variation

Maybe come soon
Shika2 reactor will work at 88km –2006 : LMA1 or LMA245 ± 37
173
121 ± 36
LMA2 =
173
LMA1 =

Nobs/Nno oscillation
Nobs/Nno oscillationz• Reactor neutrino observation summary
KamLAND has observed an evidence for reactor neutrino disappearance
at ~180km distance with 99.95% C.L.

R = 0.611 ± 0.085 ± 0.041
Assuming CPT invariance, only the LMA solution is compatible with thedeficit.
KamLAND is running on stable condition. KamLAND will give highsensitivity data to survey the LMA region.

Search for electron anti-neutrino
from the sun• How make solar anti-neutrino ?
ve with a non-zero transition magnetic moment can evolve
into ν µ , ν τ while propagating through intense magnetic
fields in the sun.

 G∆m 2
(2 N e − N n )sin 2θ
4E
 2
 ν e   ∆m 2
G
∆m 2
  Nn +sin 2θ
cos 2θ−d ν µ   4 E
2E2i  =dt  ν e  0− µBν   µ 
µB0

− µB− ν e 0ν  µ 2∆m ν e sin 2θν 4E
 µ G∆m 2Nn +cos 2θ −2E2
µB0(2 N e − N n )2∆m 2
sin 2θ
4E

G: MSW effect: spin-flavor presession
conversions : ν eL → ν µR → ν eRor

ν eL → ν µL → ν eR

depend to magnetic field model• Energy region for solar anti-neutrino

9Avoid BG by reactor
9Near of the 8B neutrino endpoint

7.5 < Ee+ < 14MeV

8.3 < Eν < 14.8MeVe• Event selection
Data: 4. Mar. – 1. Dec. 2002
Livetime: 185.5 days
Event selection criteria
spallation cut t < 2sec for dQ>106 p.e.
t < 2sec, dr(from muon track) < 3 m
for dQ>106 p.e.
dead time 11.5%
vertex cut Rp < 550 cm, Rd < 550 cm ( no thermometer cut )vertex correlation dL < 160 cm
timing correlation 0.5 < dt < 660µs
energy cut delayed: 1.8< E < 2.6MeV
detection efficiency 84.1%
energy cut prompt: 7.5 < E < 14.0 MeV

• Systematic errors
9Detection efficiency ( ε ) : 1.6 %space correlation R<550cm, dL<160cm : 1.6%
time correlation 0.5 < dt < 660 µs: 0.4%
: 0.1%
delayed energy 1.8 < Ed < 2.6 MeV

9Cross section ( σ ): 0.2 %
9Number of target proton : 4.3 %total volume error 1171 +/- 25 m3
fiducial volume ratio R<550 cm

9Energy threshold: 2.2%: 3.7%: 4.3 %

energy calibration is done by 12B beta decay

9Livetime (T): 0.07 %9Total

: 6.3 %

• Vertex calibration
with radioactive sources

with spallation events
fiducialp(n,γ)D
Balloon radius∆V= ±3.7%
Vfiducialcm
E12B

Balloon radius∆V= ±2.6%V• Energy calibration

Energy calibration with muon spallationp(n,γ)D12B

R < 550cm+/- 2.1%
for energy scale error

Assuming 8B neutrino shape : 4.3% error @ 7.5MeV threshold• Expected background
9 Reactor neutrino: 0.2 +/- 0.2

Ep > 7.5MeV, LMA region

9 Atmospheric neutrino: 0.001

T.K. Gaisser Phys. Rev. Lett. 1985

9 Fast neutron: 0.3 +/- 0.2
OD inefficiency 8% + passing rock event

9 Accidental coincidence: 0.02

pick up the off-timing events 1 < dt < 10 sec

9 8He & 9Li: 0.6 +/- 0.2

9 Total: 1.1 +/- 0.4

• Fast neutron
Delayed eventnOD pass

Prompt eventnrock

For 7.5 < Ep < 14MeV, fiducial
Fiducial 550cm

NOD-muon = 0.1 +/- 0.1
Nrock= 0.2 +/- 0.2
Total = 0.3 +/- 0.2

• 8He & 9Li

dQ > 106 p.e.
0.01 remaining BG
2sec VETO
for all volume

dQ < 106 p.e.
2sec VETO
for 6mφ cylinder
93.6% eff.

0.57 +/- 0.21
remaining BG

Total remaining BG= 0.6 +/- 0.2
for 7.5 < Ep < 14MeV• Analysis result
Reactor neutrino events

Energy region forsolar anti-neutrino
analysis

No observed event !

• The νe flux over the energy range
8.3-14.8 MeV ( 7.5 – 14 MeV for Ep )Nsignal=1.58 : using the Feldman-Cousins method
G.J.Feldman & R.D.Cousins, Phys. Rev. D57,3873(1998)Φν e =

σ = 6.88 × 10 −42 cm 2
ε = 0.841

Nsignalσ × ε × Τ × ρ p × fv

T = 1.60 × 10 7 s

ρ p × fv = 4.61 × 10 31 : number of target protons< 3.7 × 10 2 cm -2 s -1 (90% C.L.)

Normalize to 8B solar neutrino flux
This energy window is containing 29.5% of the total flux of
1.01 × 10 6 cm - 2 s -1 (BP2000)
5.05 -+0.81

Neutrino conversion probability < 2.8×10-4 (90% C.L.)
X30 improvement of the previous best measurement !
hep-ex/0310047

• Interpretation by spin-flavor precession (1)B0=5×107G at r=0.05Rsunµ=10-12µB

Our result :Solar mag. field B

8B neutrinoµBT (0.05 Rsun )3<×1.
3
1010kG
10 −12 µ B
If BT=300kG, µν<4.3×10-11µB

MUNU experiment :µν < 1.0 × 10 −10 µ B (90%C.L.)e• Interpretation by spin-flavor precession (2)

yarin
imel
pr

Magnetic field@convective zone

J.Pulido, hep-ph/0106201
Bcore<2MG
S.Chandrasekar & E.Fermi, Astrophys.J.188(1953)116

Bcore<7MG
A.Friedland & A.Gruzinov, astro-ph/0211377

Bconvective<300kG
H.M.Antia et. Al., astro-ph/0005587

yarinimelprµν<4.7×10-11µB (Bmax=300kG)µν<1.1×10-10µB (Bmax=300kG)µ11 = 10-11 µBµν<1.3×10-10µB (Bmax=300kG)

• Solar anti-neutrino summary
We got a anti-neutrino flux upper limit in the energy range 8.3 – 14.8
< 3.7 × 10 2 cm -2 s -1 (90% C.L.)
MeV

This correponds to 2.8×10-4 for BP2000 8B neutrino flux

Future studyzTotal : 9+/-6 events

Geo neutrino• Toward 7Be solar neutrino detection

We need the purification again!

• How reduce the impurity?

For 210Pb & 40K : water extraction update
distillation
For 85Kr & 39Ar : nitrogen purge system update
For Rn protection : acryl cover for systemmain guard + fresh air blow

We start R&D for detection 7Be solar neutrinos on
KamLAND !

Other studyTh-seriesU-series