Transcript KamLAND Results - INFN

KamLAND
Results
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Reactor
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KamLAND
Earth
Junpei Shirai
for the KamLAND Collaboration
Tohoku University
NOW2006, Conca Specchiulla, Italy
Sep.10-15, 2006
SUN…
KamLAND
(Kamioka Liquid scintillator
neutrino spectra from
Anit- Neutrino Detector) Expected
various sources
K.Nakamaura et al
Challenges real time
detection of
Low energy neutrinos !
Solar 
Supernova 
Geo 
Reactor 
Relic supernova 
Properties of neutrinos and
Neutrino-generation
Mechanizms in nature.
1: Reactor  experiment
2: Geo  detection
3: Solar  detection
etc.
Atmospheric 
Galactic 
1MeV
10MeV
KamLAND Collaboration
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A.Suzuki
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Tohoku University, Japan,
California Institute of Technology, USA
University Bordeaux 1, France,
Drexel University, USA,
IHEP, China,
Kansas State University, USA,
Triangle Universities Nuclear Lab., USA,
University of Alabama, USA,
University of Hawaii, USA,
University of New Mexico, USA,
University of Tennessee, USA,
Lawrence Berkeley National Lab., USA,
Louisiana State University, USA,
Stanford University, USA
~90 physicists from 14 Institutes
KamLAND Reacotor
experiment
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Challenging the Solar Neutrino
Problem (SNP)
Long History since late 1960's!
Cl, H2O, Ga experiments all showed
significantly less flux than the SSM prediction.
[SNP]
Neutrino oscillation naturally explained the
results, but several solutions existed in (m2mixing angle) plane.
SNO discovered active non-e component in
the flux by using both CC (only e) and NC
(total active ’s) reactions. This strongly
suggests neutrino oscillation.
The LMA (m2~105eV2) solution seems quite
promising, but no single experiment uniquely
determined the solution.
A decisive experiment is needed using man-made neutrinos.
Reactor experiments have played a crucial role in this point !
Reactor: powerful tool for
studying neutrino oscillation
Long history since the first detection of neutrinos by F.Reines in 1950's.
Pure and high intensity neutrino "beam" is provided.
n+235U→X+Y+2n
Fission products: neutron rich → - decays→[~6 e's]+[~200MeV]/fission
Typical power reactor (3GWth)→ 5.6×1020 e /s, ~1/4 is detected by
e p→e+n
2 m2L is obtained
A
large
L/E
factor
in
sin
<
The energy is low: E ~ 8.5MeV→
4E
2
to be sensitive to small m .
The flux and the spectrum of e are well understood.
[Power reactors]
Isotopic components of the fuel elements
(235U, 239Pu, 238U, 241Pu) are estimated by
the initial ones and the thermal power.
The flux and spectrum of each element is
studied and the total flux uncertainty is ~2% !
Reactor experiments
Reactor
e
Disappearance experiment
m2L
2
2
1-sin 2sin
4E
(L: flight distance)
e
Detector
e
No e oscillation up to a distance
L~ O(1)km (m2<O(10-3) eV2).
Neutrino flux has been well understood.
Cross section of e p→e+n has been
understood very precisely (0.2%).
The technique using a large volume (~10tons)
liquid scintillator has been established.
Nobs./Nno-oscil
Before KamLAND,
e p→e+n
Liquid
scintillator
53 Japanese power reactors.
26 are concentrated at
L=138-214km with 80GWth!
KamLAND reactor
neutrino
experiments
KamLAND
1000ton LS
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With ~100 times larger L/E than
Kamioka
before KamLAND is sensitive to
m2 ~10-5eV2 and can test the
solar LMA solution!
KamLAND Detector
Rn free air
Calibration
device
Rock
Site: Kamioka underground
mine, Gifu prefect., 2700m.w.e.
Cosmic muon rate: 0.34Hz
Central
Detector
Stainless steel tank (18m)
LS(Normal dodecane(80%)+Pseudocumene(20%) +PPO(1.5g/l))
13m
Balloon(135mt; EVOH/3Ny/EVOH)
Buffer oil (Normal dodecane+ isoparaffin: 2.5mt, LS-BO=-0.04%)
1325 17”PMTs+554 20”PMTs
(34% of 4, 350p.e./MeV,
t~1.9ns (17”PMT))
Outer Detector
20m
Pure water (3.2kton)
225 20”PMTs
Mt.Ikenoyama
1km
KamLAND area
Detector
2.2km
Control room
Rn-free
gas system
Water purification system
To the mine
entrance

e
detection in KamLAND
e+ + n
 +p
[E1.8MeV]

e
p
Te+
+
e
(0.51) [Prompt e+ signal]
Eprompt
=Te++ annihilation 's
=E-0.8MeV
e
(0.51)
n
(2.2MeV)
~200s
p
d
Time and space correlation, and
Delayed  energy
→ Significant reduction of backgorunds
[Delayed  by
neutron capture]
Results of reactor 
1st
Period
Exposure
(ton・y)
|rp|,|rd|(m
)
|rp-rd| (m)
Tp-d (s)
Ed (MeV)
Ep (MeV)
Nno-osc.exp
Nobs
Nbkg ]
[N -N
obs
bkg
Nno-osc.exp
Mar.4Oct.6, '02
2nd
Mar.9, '02Jan.11,'04
162
766
< 5m
5.5
1.6 m
2
0.5-660
1.8-2.6
> 2.6
86.8±5.6
0.5-1000
Same
2.6-8.5
365±23.7
258
17.8±7.3
54
1±1
0.611±
0.085±0.041
0.658±
0.044±0.047
Disappearance !
[99.95%CL]
Phys.Rev.Lett. 94, 081801 (2005)
[99.998%CL]
2.6MeV
Spectral Distortion
Oscillatory
behavior
L0/E distribution (180km)
Decoherence
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Decay
Oscillation
Solar+KamLAND
eV2
12
4 11
m2 (eV)2
m2
10-4
×10-5
10
9
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8
10-5
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7
6
0.1
1
tan2
10
5
tan2
Oscillation
parameters
are precisely
Determined !
Δm2=
+0.6
7.9 -0.5 ×10-5eV2
tan2θ= 0.4 +0.10
-0.07
Prospects of KamLAND
reactor expereiment
Keep data taking !
Reduce systematic error by a new calibration system
in place of the vertical-axis calibration.
Systematic error : 6.5%
3% rate error
1% scale error
3kt-yr data taking
Detector
(%)
Fiducial vol.
4.7
Energy threshold 2.3
Efficiency of cuts 1.6
Live time
0.06
Reactor power
2.1
Fuel composition 1.0
e spectra
2.5
Cross section
0.2
“4 system”
Now ready !
KamALND: challenging
Geoneutrinos
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Large heatflow from the Earth
~60mW/m2
Measured points
>20,000
44.2±1.0 TW (Pollack, '93),
31±1 TW (Hofmeister, '05)
(~10,000 power reactors)
The heat source has not been well understood.
Volcanoes, earthquakes,
Plate tectonics,
Dynamics of
Plume tectonics,
the Earth
Magnetic field of the Earth
Radiogenic heat has been considered to be very important!
Carbonacious chondrite :
Chemical component of the earth
[BSE (Bulk Silicate Earth) model]
19TW
238U(8TW),
232Th(8TW),
40K(3TW)
Geoneutrinos as a probe of
Radiogenic Heat
Direct information of radiogenic heat ! (Eder('66), Marx('69))
6 e+51.7MeV
232Th→208Pb: 4
 +42.7MeV
238U→206Pb:
e+1.31MeV
40K→ 40Ca+e-+
[89%]
e
KamLAND
e p  e n
208
40K

.5
1
Tl
228
234
Pa
Ac
238U
232Th
212
1.5
2
1.8MeV

Bi
2.5
214
3
Bi
3.27MeV
KamLAND: Geo- Analysis
Data sample: Live-time 749.1±0.5 days (Mar.'02-Nov.'04)
Selection conditions (after the on cut)
Low energy (<3.3MeV)
Background (external , radio-impurity)
[Geo 
[2nd reactor]
<5.5m
< 2m
Fiducial vol (|rp|, |rd|) < 5m
|rp-rd|
< 1m
Tp-d 0.5s- 500s
Eprompt 0.9-2.6MeV
same
Ed
0.5s- 1000s
2.6-8.5MeV
1.8-2.6MeV
Efficiency (68.7±0.7)%
(89.8±1.5)%
Energy spectra in KamLAND
Events/0.17MeV
Geo-ν
Nature 436, 499 (2005)
Reactor 
Data
(42±11)
Accidentals
(2.38±0.01)
Reactor ν
Th
(80.4±7.2)
U, Th prediction
of the Earth
model (16TW)
U
Antineutrino Energy E(MeV)
Observed: 152 events
Estimated BG: 127±13 events
25
+19
-18
events
Rate+Shape analysis
Th/U mass ratio=3.9
The Earth model
(Th/U mass ratio
=3.9) U+Th=19
90%CL
2
NU+NTh(eventa)
U/Th free
(NU-NTh)/(NU+NTh)
U+Th=21
(U=3, Th=18)
Radiogenic Power
< 60TW (99%CL)
4.5
54.2
NU+NTh (events)
U+Th=28
Consistent with the rate
+19
analysis (25 -18 ) and the
Earth model (19) within 1σ.
(,n) Background
222Rn
210Pb
210Bi
(t1/2=22.3y)
210Po
5.3MeV)
206Pb
Quenched,
21.1Bq/FV
Geo
Reactor
n+p→n+p
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13C→16O(*)+n
[1%]
12C*
16O*
Primary
16O*→,
e+e(~6MeV)
n+p→n+p
n+12C→12C*(4.4)+n
Secondary
n+p→d+
Uncetainty: 26%
Cross section 20%
210Po rate 14%
Proton quench 10%
4% (New data)
Events <0.9MeV
Measurement
with n beam
Reduce uncertaity of (,n)
Measurement of the proton quenching factor in n+p→n+p.
Hit the LS with mono-energetic
neutrons to measure visible energy
of the recoil proton in n+p→n+p.
Neutron detectors
(En, n)
LS sample
OKTAVIAN @OSAKA Univ.
Measure (,n) events in KamLAND below 0.9MeV; pure (,n) events to know
210Po decay rate. → Continued, Needs statistics.
New cross section data of 13C(,n)16O.
Harissopulous et al. (2005), sys. uncertaity 20%→4%.
KamLAND
7Be Solar Neutrino
Detection
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Towards 7Be solar 
KamLAND
SuperK
SNO
7Be
: Second largest flux.
Theoretical Uncertainty is large (10%).
No direct measurement so far.
7Be
(862KeV)
300KeV
5MeV
Detection by KamLAND
e-→eSingle ionization event
with Evis<665KeV.
Long lived 210Pb(T1/2=22.3y) and 85Kr(T1/2=10.8y) in
the LS must be removed by factors ~105!
Purification of the 1000 ton LS
Lead removal
LS
Purification
Method
Purification by
Distillation (210Pb)
&
N2 purge (85Kr)
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LS
1.5m3/hr
Distillation tower
Next year !
KamLAND
area
Tanks
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Test plant
(Tohoku
University)
(~3×10-5 reduction)
N2-purge
tower
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7Be
(no oscillation)
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Construction of the
purification system
is finished this month !
Reactor neutrino
Prompt Energy (MeV)
Reactor 
5m
5.5m
6.5m
Reactor & Geoafter purification
16O*
14C*
(,n)
Geo 
Fast neutrons
accidental
Fid. Volume
No (,n) &
Reduced accidentals
Fiducial volume is
enlarged !
(R/6.5m)3
No reactor case
After
purification
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±35%
The same data taking period
with enlarged fiducial volume.
±54%(now)
Total data
±28%
<30TW(99%CL)
Check the
Earth model !
Towards pep/CNO  detection
After removal of 210Pb and 85Kr, 11C which is
generated by muons makes a dominant BG in 1~2 MeV
region for pep/CNO  detection.
10-6 reduction of 210Pb, 85Kr assumed
11C→11B+e++
=29.4m, Q=1.98MeV
pep
Remove
~95% of
11C
11C
by 3-fold coincidence
production is accompanied by neutrons
12C+X→11C+n+Y+…
X=,n,p,,e,
t
Take 3-fold coincidence:
1) Muon
2) Neutron (2.2MeV
 after ~200s)
3) 11C decay(=29.4m)
+ signal
1.0
KamLAND
11C detection
1.2
1.4
1.6
1.8
2.0
Visible energy (MeV)
11C-n
select L<50cm,
#ndetected>0)
200cm
R
Pep/CNO : prospects
3 years data
7Be
pep
CNO
11C
Issues:
New electronics to detect neutrons after the large
muon signal (design finished).
Next slide
Improve muon fitter and muon tracking device.
5% of
11C
remains.
High multiplicity events after
the muon (spallation neutrons)
with absolutely zero dead-time
and quick recovery
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Main
Electronics for 11C tagging
Design finalized
Circuit
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Analogue
Front End
Circuit
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×12 /main board
8B
solar 
To find upturn toward the low energy by the Matter effect.
232Th
concentration in the LS is
(5.2±0.8)×10-17 g/g from Bi→Po decay.
208Tl
(→, 5MeV) in the LS
dominates the signal.
232Th: 212Bi→212Po
KamLAND
(64%)
212Bi
0.17Bq/m3
(36%)
208Tl
212Po


208Pb
from Pena-Garay
Mar-Sep,2002
If Th is removed by purification
to ~10-3, then we have a chance !
KamLAND: Summary
KamLAND has established e oscillation. Under the CPT
invariance the SNP has been solved and oscillation parameters
have been determined.
New "4 calibration system" has been ready for significant
reduction of systematic errors to get improved measurement of
oscillation parameters.
First challenge of Geo-neutrino detection has been made by
KamLAND. Further reduction of systematic uncertainty of (,n)
background is underway.
Construction of a new purification system is finished this month
and we start LS purification right away.
KamLAND enters the solar phase next year. High quality data of
reactor and geo-neutrinos will also be obtained.