Transcript スライド 1 - Istituto Nazionale di Fisica Nucleare

KamLAND Future Prospects
Atsuto Suzuki
Tohoku University
KamLAND Collaboration
III Int. Workshop on Neutrino Oscillations in Venice
Feb. 7-10, 2006
Outline
1. KamLAND-II
2. Prospects of Solar Neutrino Detection
3. Toward Precise Measurement of
Reactor Neutrinos
4. More and more Geoneutrinos
5. Conclusions
1. KamLAND-II (summer in 2006)
※ 7Be solar neutrino detection:
JSPS 5-year project from 2004
※ Precise measurements of reactor-, geo- and solar neutrinos:
MEXT 5-year project from 2005
300
KamLAND-II
2. Prospects of Solar Neutrino Detection
single events in KamLAND
10-5 ~ 10-6
distillation
test bench
Test Bench Studies
212Pb
222Rn
R~10-2
222Rn
:
4x10-3 >R > 5x10-4
85Kr :
4x10-5 >R > 5x10-6
N2 purge
test bench
Background Reduction Status
impurities
present
(3.5 ± 0.5) x 10-18 g/g
232Th (5.2 ± 0.8) x 10-17 g/g
40K
< 2.7 x 10-16 g/g
85Kr ~ 1
Bq/m3
210Pb
~ 10-20 g/g
238U
goal
reduction
10-16 g/g
10-16 g/g
10-18 g/g
~1 mBq/m3
~10-25 g/g
OK
OK
10-2
10-6
10-5
distillation purge
< 10-2
< 10-5
< 10-4
< 10-5
purification system
installation :
until this July
space for new purification system
(May 2005)
Expected Energy Spectrum in KamLAND-II
100 days data
210Po
85Kr
events (0.3 <E< 0.8 MeV) / day / fid. (R< 4m)
7Be (80) , CNO (16), pep (4) ,
85Kr (8), 210Bi (<2), 210Po (<1), 40K (3)
Seasonal Flux Variation of Solar Neutrinos
3 years data in KamLAND-II
events (0.3 <E< 0.8 MeV)/ day / fid. (R < 4m)
7Be (80) , CNO (16), pep (4) ,
85Kr (8), 210Bi (<2), 210Po (<1), 40K (3)
Possibility to Detect CNO and pep Neutrinos
CNO+pep
11C
Identification
DL < 50 cm along m
:
# of neutrons > 0
11C with DR < 150 cm
Present KamLAND Data
Dt
(DR : distance from the nearest n)
100
200
(min.)
energy
1.2
1.4
1.6
1.8 (MeV)
DR
200
400
600
800
(cm)
New Electronics for Identifying
Successive Multiple Events
new (dead-time free)
Expected Energy Spectrum in
CNO+pep Region
90% rejection of 11C
3 years data
7Be
pep
CNO
11C
background subtracted
7Be
neutron tagging efficiency
~ 100%
3 years data
CNO
pep
3. Toward Precise Measurement of
Reactor Neutrinos
( ne  nx : 2-flavor case )
shape-analysis
Nobs – NBG
Nexpected
LMA II: disfavored
at 98.0% CL
LAM I
= 0.686 ± 0.044 (stat)
± 0.045 (syst)
disappearance:
99.995 % CL
LAM 0: disfavored
at 97.5% CL
Improvement of Detector Systematic Error
energy scale, timing,
g detection,
n capture time,
n detection,
trigger efficiency,
light transport,….
6.5 %  4 %
total uncertainty
g
n
12N, 12B,…
m
radioactive sources, laser
system, LEDs,
cosmic-ray m, m –induced
spallation products
: 1.012
MeV (g + System
g)
Off-Axis
Calibration
65
68Ge
Zn
: 1.116 MeV (g)
60Co
: 2.506 MeV (g + g)
AmBe : 2.20 , 4.40, 7.6 MeV (g)
Setting Off-Axis System
Updated Oscillation Parameters
statistics x 5
systematic error : 4%
statistics x 5
statistics x 10
systematic error : 4%
statistics x 10
limit due to
4% systematic error
4. More and More Geoneutrinos
ne
ne
ne
G. Gamow: 1953
ne
ne
Geoneutrino Result in KamLAND
Background
KamLAND
Accidental
Coincidence
Events/0.17 MeV
13C
(a,n)
16O
Reactor ne
short lived
long lived
Th
U
Antineutrino Energy (MeV)
Total
signal
# of
events
2.38
±0.01
42
±11
best
fit
80.4
±7.2
1.9
±0.2
127
±13
152
Constraints on FU +FTh & FU /FTh
in KamLAND-II
Th/U~3.9
NU + NTh
CL 68.3%
CL 95.4%
CL 99.7%
BSE model
best fit
best fit
(NU – NTh)/(NU + NTh)
2 years data in KamLAND-II
2 years data in KamLAND-II
Th/U~3.9
Conclusions
KamLAND-II provides
• high rate detection of 7Be solar neutrinos,
• chance to detect CNO + pep solar neutrinos,
• stringent constraint on Dm2 for reactor neutrinos,
• more constraint on U+Th (geoneutrinos),
and
• interesting test of U/Th (geoneutrinos)