Antineutrino Physics in KamLAND Atsuto Suzuki High Energy Accelerator Research Organization (KEK) 1....
Transcript of Antineutrino Physics in KamLAND Atsuto Suzuki High Energy Accelerator Research Organization (KEK) 1....
Antineutrino Physics in KamLANDAntineutrino Physics in KamLAND
Atsuto SuzukiAtsuto SuzukiHigh Energy Accelerator Research Organization (KEK)High Energy Accelerator Research Organization (KEK)High Energy Accelerator Research Organization (KEK)High Energy Accelerator Research Organization (KEK)
1. KamLAND Experiment
2. Reactor Antineutrino Oscillation
Study
3. Geological Antineutrino Detection
4. Conclusions
1. KamLAND Experiment
2. Reactor Antineutrino Oscillation
Study
3. Geological Antineutrino Detection
4. Conclusions
JINR Scientific Council, January 19, 2007JINR Scientific Council, January 19, 2007
KamLAND: 3KamLAND: 3rdrd Generation Experiment at Kamioka Generation Experiment at Kamioka
33rdrd generation generationKamLANDKamLAND
::1000 ton 1000 ton
Liquid Scintillator DetectorLiquid Scintillator Detector
22ndnd generation generationSuper-KamiokandeSuper-Kamiokande
::50,000 ton50,000 ton
Water Cerenkov DetectorWater Cerenkov Detector(1996 ~ )(1996 ~ )
1994: proposal1994: proposal1997: Budget was approved.1997: Budget was approved. Construction started.Construction started.1999: Japan-US collaboration1999: Japan-US collaboration2002: Data-taking started.2002: Data-taking started.
HistoryHistory
11stst generation generationKamiokandeKamiokande
::3000 ton 3000 ton
Water Cerenkov DetectorWater Cerenkov Detector(1983 - 1997)(1983 - 1997)
13 m
18 m
detector location: old Kamiokande site : 2700 m.w.e.
water Cerenkov outer detector
1000 ton liquid scintillator : 80% (dodecane) + 20% (pseudocumene) + 1.52 g/l PPO : housed in spherical plastic balloon
1325x17-inch + 554x20-inch PMT’s
photocathode coverage : 34%energy resolution : 6.2 %/(E:MeV)1/2
3000 m3 stainless steel vessel
KamLAND DetectorKamLAND Detector
: filled with a mixture of paraffin oil and dodecane ( = 0.04%)
inner view of spherical vessel
180 km
300
1. KamLAND Experiment1. KamLAND Experiment
Kamioka Liquid scintillator AntiNeutrino Detector
1000 ton liquid scintillator detector1000 ton liquid scintillator detector
77Be, CNO+pepBe, CNO+pep
KamLAND Data Samples for KamLAND Data Samples for OutcomesOutcomes
Mar. 9, 2002 – Oct. 30, 2004(live time = 749.1 days)
Mar. 4 – Oct. 6, 2002(live time = 145.4 days)
Mar. 9, 2002 – Jan. 11, 2004(live time = 515.1 days)
physics runphysics run
calibration runcalibration run
test/bad runtest/bad run
1st reactor result : Evidence for Reactor Antineutrino Disappearance
2nd reactor result : Evidence of Spectral Distortion
1st geoneutrino result : Experimental Investigation of Geologically Produced Antineutrinos
2002 2003 2004
Nuclear Power-Stations around KamiokaNuclear Power-Stations around Kamioka
Kamioka
Kashiwazaki : world biggest power
station (24.3 GW)
70 GW (~7 % of world totalpower generation)
atL ~ (175 ± 35) km
70 GW (~7 % of world totalpower generation)
atL ~ (175 ± 35) km
huge powerhuge powernearly equal distancenearly equal distance
long baseline (180 km)long baseline (180 km)
⇩⇩Kamioka :Kamioka :
suitable location forsuitable location forneutrino oscillation studyneutrino oscillation study
huge powerhuge powernearly equal distancenearly equal distance
long baseline (180 km)long baseline (180 km)
⇩⇩Kamioka :Kamioka :
suitable location forsuitable location forneutrino oscillation studyneutrino oscillation study
commercial reactors : 53 nominal power output : 152 GW
in Japan
distance from Kamioka (km)
no
. o
f n
eutr
ino
s 86%:(175 ±35)km 97%: Japanese stations 2.2%: Korean 〃 〃 0.2%: European 〃 〃 0.12%: Taiwanese〃 〃 0.12 %: North American〃
ReactorReactor e Contribution at KamiokaContribution at Kamioka
e
~210 s
How to Detect How to Detect e e in Liquid Scintillatorin Liquid Scintillator
inverse – decay :inverse – decay :
p(2.2 MeV)
n
e+
d
delayed coincidence method : delayed coincidence method : prompt eprompt e++ + delayed + delayed (2.2 MeV) (2.2 MeV)delayed coincidence method : delayed coincidence method : prompt eprompt e++ + delayed + delayed (2.2 MeV) (2.2 MeV)
ee + p + p e e++ + n + nee + p + p e e++ + n + n
E ~ Ee+ + 0.8 MeVEth = 1.8 MeV
high rejection-power for background eventshigh rejection-power for background eventshigh rejection-power for background eventshigh rejection-power for background events
prompt signal
delayed signal
2.6 MeV <Eprompt< 8.5 MeV
1.8 MeV <Edelayed< 2.6 MeV
Expect 1.5 n-Expect 1.5 n-1212CCcapturescaptures
AccidentalAccidentalbackgroundbackground
geoneutrino regiongeoneutrino region2.6 MeV
Prompt vs. Delayed EnergyPrompt vs. Delayed Energyfor for ee Candidate Events Candidate Events
expected( no oscillation)
observed
Evidence for Reactor Evidence for Reactor ee Disappearance Disappearance
exposure 766.3 ton•yr observed ev. 258 expected ev. 365 ± 24background ev. 17.8 ± 7.3
(Nobs – NBG)/Nexpected
= 0.686 ± 0.044 (stat) ± 0.045 (syst)disappearance with 99.995 % CL
Time Dependence of Event RateTime Dependence of Event Rate
Evidence of Reactor Evidence of Reactor ee Spectral Distortion Spectral Distortion
Null Shape-DistortionNull Shape-Distortion
excluded at 99.8 % CLexcluded at 99.8 % CL
2-Flavor Oscillation Fit
2-Flavor Oscillation Fit best fit with
rate + spectrum shape
m2 (eV2) = 7.9 x 10-5
sin2 2= 0.98
un-binned likelihood fit : d.o.f. = 24.2/17
best fit withrate + spectrum shape
m2 (eV2) = 7.9 x 10-5
sin2 2= 0.98
un-binned likelihood fit : d.o.f. = 24.2/17
+0.6- 0.5
allowedallowed
LMA-II
LMA-I
LMA-0
allowedallowed
mm22 = 8.0 x 10 = 8.0 x 10-5-5 eV eV22 , sin , sin22 2 2 = 0.98 = 0.98
Constraints on Oscillation Constraints on Oscillation ParametersParameters
disfavored at 97.5% C.L.
disfavored at 98.0% C.L.
event rateevent rate spectral shapespectral shape++ee xx
excludedexcluded
LMALMA
Observation of Neutrino Oscillation PatternObservation of Neutrino Oscillation Pattern
(L(L00≡≡180 km)180 km)
evidence of evidence of neutrino oscillationneutrino oscillationat at 99.99. 88 % % C.L. !!!C.L. !!!
evidence of evidence of neutrino oscillationneutrino oscillationat at 99.99. 88 % % C.L. !!!C.L. !!!
No
bs /
Ne
xpdefinite baseline (~ 180 km) definite baseline (~ 180 km) ⇒ ⇒ test oscillation hypothesistest oscillation hypothesis
Δm2=7.9x10-5 eV2 sin22θ=0.98
L/E (km/MeV)
2-Flavor Oscillations (All Solar + KamLAND)2-Flavor Oscillations (All Solar + KamLAND)
assuming CPT invarianceassuming CPT invariance
the most precise determinationthe most precise determinationofof mm22 to dateto date
the most precise determinationthe most precise determinationofof mm22 to dateto date
m2 = 7.9 x 10-5 eV2
tan2 = 0.40
m2 = 7.9 x 10-5 eV2
tan2 = 0.40
+ 0.6– 0.5
+ 0.09– 0.07
A. Smirnov, 2002
Solutions to Solar Neutrino ProblemSolutions to Solar Neutrino Problem
KamLAND solved the solar neutrino problem KamLAND solved the solar neutrino problem under the laboratory conditions (J. Bahcall)under the laboratory conditions (J. Bahcall)
KamLAND solved the solar neutrino problem KamLAND solved the solar neutrino problem under the laboratory conditions (J. Bahcall)under the laboratory conditions (J. Bahcall)
U, Th, K decays:U, Th, K decays:radiogenic heatradiogenic heatU, Th, K decays:U, Th, K decays:radiogenic heatradiogenic heat
Experimental Investigation of Geologically Produced Antineutrinos
Experimental Investigation of Geologically Produced Antineutrinos
e
e
Heat GenerationHeat Generation::
basic factorbasic factor
Heat GenerationHeat Generation::
basic factorbasic factor
Interior DynamicsInterior DynamicsInterior DynamicsInterior Dynamics
Formation History Formation History Formation History Formation History
geoneutrino geoneutrino detectiondetection
Heat Balance between Heat Balance between Dissipation and Generation Dissipation and Generation
heat dissipationheat dissipation44 TW or 31 TW44 TW or 31 TW
mW m-2
coolingcooling ~20 TW ???~20 TW ???
radiogenic
~20 TW ???
generationgenerationnew idea : new idea : georeactorgeoreactor??????????????????
≡≡
U
U+Th
Nu
mb
er
of
anti
neu
trin
os
(1/M
eV
/de
cay
)
Antineutrino
1.8 MeV1.8 MeV
ee Energy Spectra of Energy Spectra of 238238U, U, 232232Th and Th and 4040K DecaysK Decays238U 206Pb + 8 4He + 6 e- + 6 e + 51.7 MeV
232Th 208Pb + 6 4He + 4 e- + 4 e + 42.7 MeV
40K 40Ca + e- + e + 1.31 MeV (89.3 %)40K + e- 40Ar + e + 1.51 MeV (10.7 %)
238U 206Pb + 8 4He + 6 e- + 6 e + 51.7 MeV
232Th 208Pb + 6 4He + 4 e- + 4 e + 42.7 MeV
40K 40Ca + e- + e + 1.31 MeV (89.3 %)40K + e- 40Ar + e + 1.51 MeV (10.7 %)
CoreMantle
CrustCrust
Sediment
Our Reference Earth ModelOur Reference Earth Model
[Th] /[U[Th] /[U] ~] ~ 3.93.9
outer / innerouter / inner U: 0, Th: 0U: 0, Th: 0outer / innerouter / inner U: 0, Th: 0U: 0, Th: 0
(units: ppm)(units: ppm)
continentalcontinental U: 2.8, U: 2.8, Th: 10.7Th: 10.7oceanicoceanic U: 1.7, U: 1.7, Th: 6.9Th: 6.9
continentalcontinental U: 2.8, U: 2.8, Th: 10.7Th: 10.7oceanicoceanic U: 1.7, U: 1.7, Th: 6.9Th: 6.9
upper / lowerupper / lower U: 0.012, Th: 0.048U: 0.012, Th: 0.048upper / lowerupper / lower U: 0.012, Th: 0.048U: 0.012, Th: 0.048
upper upper U: 2.8, Th: 10.7U: 2.8, Th: 10.7middlemiddle U: 1.6, Th: 6.1U: 1.6, Th: 6.1lowerlower U: 0.2, Th: 1.2 U: 0.2, Th: 1.2
upper upper U: 2.8, Th: 10.7U: 2.8, Th: 10.7middlemiddle U: 1.6, Th: 6.1U: 1.6, Th: 6.1lowerlower U: 0.2, Th: 1.2 U: 0.2, Th: 1.2
U: 0.10, Th: 0.22U: 0.10, Th: 0.22U: 0.10, Th: 0.22U: 0.10, Th: 0.22
geoneutrino production pointsgeoneutrino production pointsobserved by KamLANDobserved by KamLAND
km
km
Geoneutrino ProductionGeoneutrino Productionin Our Reference Modelin Our Reference Model
crustcrust
mantlemantle
sedimentsedimentCu
mu
lati
ve F
lux
(1/c
m2/s
ec)
cumulative geoneutrino fluxcumulative geoneutrino flux (U-chain)(U-chain)
~70%~70%
~25%~25%
<5%<5%
Antineutrino Energy (MeV)Antineutrino Energy (MeV)
Eve
nts
/0.1
7 M
eVE
ven
ts/0
.17
MeV
[U][U]++[Th][Th] = 19 ev = 19 ev
2.382.38
±0.01±0.01Accidental Accidental Coincidence Coincidence
# of # of eventseventsBackgroundBackground
127 127 ±13±13TotalTotal
best best fitfit
80.480.4
±7.2±7.2
1.9 1.9 ±0.2±0.2
Reactor Reactor ee
short livedshort lived
long livedlong lived
42 42 ±11±11
1313C (C (,n,n) ) 1616OO
Energy Distributions of Energy Distributions of Candidate & Background EventsCandidate & Background Events
signal 152
# of geoneutrinos:25 events
Maximum Likelihood Analysis Maximum Likelihood Analysis for Geoneutrino Flux for Geoneutrino Flux
# of U,Th: free parameter,# of U,Th: free parameter,mm22,sin,sin2222: best fit value: best fit value±1±1, , 1313C(C(,n),n)1616O: peak width & height: free parameterO: peak width & height: free parameter
confidence interval for # of detected geoneutrinosconfidence interval for # of detected geoneutrinos
(NU – NTh)/(NU + NTh)
NU +
NT
h
best fitbest fit
CL 68.3%CL 95.4%CL 99.7%
Th/U~3.9Th/U~3.9Th/U~3.9Th/U~3.9
reference reference modelmodel
reference reference modelmodel
First Geoneutrino ResultsFirst Geoneutrino Results
Assuming Th/U~3.9Assuming Th/U~3.9
2828
22
KamLAND observedKamLAND observedKamLAND observedKamLAND observed
total number of geoneutrinostotal number of geoneutrinos:: U+Th (best fit) : 28U+Th (best fit) : 28 U+Th (rate analysis) : 25U+Th (rate analysis) : 25
BSE predictionBSE prediction
1.45x101.45x10-31-31 ee/(target proton year)•/(target proton year)• 1.62x101.62x1077 cm cm-2-2ss-1-1 at KamLAND at KamLAND 60 TW from our reference model60 TW from our reference model
99% confidence upper limit of 99% confidence upper limit of ee flux flux::
ConclusionConclusion
KamLAND Collaboration (China-France-Japan-US)KamLAND Collaboration (China-France-Japan-US)
13C (,n) 16O* Correlated Background 13C (,n) 16O* Correlated Background
source in LSsource in LS206Pb210Bi 210Po210Pb
5.013 d22.3 y stable138.4 d
(long-lived Rn decay product)
p12C*
(4.4 MeV)
prompt
16O*
np
recoil proton+
(6.13 MeV) e+e- (6.05MeV)
prompt
n
delayed
(2.2 MeV)
13C+
17O*
( 1.1% in 12C)
recoil proton
Survived Background
Sources
Survived Background
Sources
BackgroundBackground # of # of eventsevents
99Li/Li/88HeHe 4.8 4.8 ±0.9±0.9
Accidental Accidental
CoincidenceCoincidence
2.692.69
±0.02±0.02
Fast NeutronFast Neutron
1313C (C (,n,n) ) 1616O* O*
< 0.89< 0.89
10.310.3
±7.1±7.1
TotalTotal 17.8 17.8 ±7.3±7.3
Qdeposit > 106 p.e. T < 0.5 s0.5< T< 1 ms R < 2 m
n
9Li
9Be8Be+n
:178.3 ms
9Li
background rate: 0.03 ev/daybackground rate: 0.03 ev/day
Nob
s/Nn
o osci
llat
ion
Ratio of Observed to Expected Ratio of Observed to Expected ee Flux for Reactor Neutrino Flux for Reactor Neutrino
ExperimentsExperiments
KamLANDKamLAND
LMA: LMA: mm22 = 5.5x10 = 5.5x10-5-5 eV eV22
sinsin22 2 2 = 0.833 = 0.833
LMA: LMA: mm22 = 5.5x10 = 5.5x10-5-5 eV eV22
sinsin22 2 2 = 0.833 = 0.833
neutrino tomographyneutrino tomographyFuture PlanFuture Plan
SNO+
Finland
KamLAND
e Event Selection e Event Selection
① inverse - decay selection 2.6 < Eprompt < 8.5 MeV 1.8 < Edelay <2.6 MeV 0.5 < T< 1000s L < 2 m no OD signals tagging efficiency 89.8%
② -induced spallation event cut T < 2 s for showering/bad
T < 2 s & L< 3m along dead-time 9.7%
③ fiducial selection
R < 5.5 m : 543.7 ton
④ data sample (2nd result): 515.1 days exposure time = 766.3 ton-year
prompt
delayed
More exotic, non-oscillations models for the antineutrinoMore exotic, non-oscillations models for the antineutrinochannel start being less favored by datachannel start being less favored by data
DecayDecay**
excluded atexcluded at95% CL95% CL
*V.Barger et al. Phys. Rev. Lett. 82 (1999) 2640
DecoherenceDecoherence††
excluded atexcluded at94% CL94% CL
†E.Lisi et al., Phys. Rev. Lett. 85 (2000) 1166
Geoneutrino Fathers and Grandfather
Geoneutrino Fathers and Grandfather
Fathers :Fathers : G. Eder, G. Eder, Terrestrial Neutrinos, Terrestrial Neutrinos, Nucl. Phys. 78, 657 (1966)Nucl. Phys. 78, 657 (1966) G.G. Marx, Geophysics by Neutrinos, Geophysics by Neutrinos,
Grandfather :Grandfather : G. Gamow, G. Gamow, Letter to F. Reines (1953) Letter to F. Reines (1953)
Czechoslovak Czechoslovak J. Phys. B19, 1471 (1969)J. Phys. B19, 1471 (1969)Czechoslovak Czechoslovak J. Phys. B19, 1471 (1969)J. Phys. B19, 1471 (1969)
Space and Time Correlations between Prompt and Delayed
Events
Space and Time Correlations between Prompt and Delayed
Events0.5<T<500 s
0<L<100 cm0.9<Eprompt <2.7 MeV
T
L
SystematicSystematic %%
Scintillator volumeScintillator volume 2.12.1
Fiducial fractionFiducial fraction 4.24.2
Energy threshold Energy threshold 2.32.3
Cuts efficiencyCuts efficiency 1.61.6
Live timeLive time 0.060.06
Reactor PReactor Pthermalthermal 2.12.1
Fuel compositionFuel composition 1.01.0
Time lagTime lag 0.010.01
Antineutrino Antineutrino spectrumspectrum 2.52.5
Antineutrino x-Antineutrino x-sectionsection 0.20.2
TotalTotal 6.56.5
Systematic ErrorsSystematic Errors(for reactor neutrino flux)
150 s <T< 10 msL < 3 m
12B
12N
12B12N
τ=29.1msQ=13.4MeV
τ=15.9msQ=17.3MeV
distribution: distribution: uniformly in spaceuniformly in space
2. Oscillation Studies by Reactor Antineutrinos2. Oscillation Studies by Reactor Antineutrinos
Reactor AntineutrinosReactor Antineutrinos
235U + n N1+ N2+ xn +6.1 + 6.1 e + (201.8±0.5 MeV)
Nuclear reactors are very intense sources of Nuclear reactors are very intense sources of ee from from the the -decays of neutron-rich fragments :-decays of neutron-rich fragments :
EEprompt prompt (e(e++) = E) = E- 0.8 MeV- 0.8 MeV
2-step signature :2-step signature :
prompt : prompt : ee++ ionization, annihilation ionization, annihilation
delayed : thermal neutron capture on delayed : thermal neutron capture on ppEEdelayed delayed (() = 2.2 MeV, ) = 2.2 MeV, t ~ 200 t ~ 200 ss
Antineutrinos are detected through inverse Antineutrinos are detected through inverse -decay : -decay :
e + p e+ + nEEthth = 1.8 MeV = 1.8 MeV
1/3 of total e’s
ννee+p→n+e+p→n+e++ cross sectioncross sectionννee+p→n+e+p→n+e++
cross sectioncross section
Ev (MeV)
13C( , n) 16O*
(n, p) 12C(n, n) 12C
13C( , n) 16O
Expected Energy Expected Energy Spectra of 13C (,n) 16O*, 16O Correlated Events
Expected Energy Expected Energy Spectra of 13C (,n) 16O*, 16O Correlated Events
free parameter in likelihood analysis free parameter in likelihood analysis peak height for reactor neutrinospeak height for reactor neutrinos peak height & width for geoneutrinos peak height & width for geoneutrinos
reactorreactorgeo-geo-
expected (no oscillation)
observed
Time Dependence of Observed Event Rate
Time Dependence of Observed Event Rate
90% CL
···· ···· best fitbest fit
fit constrained through
expected background
(0.03 events/day)(0.03 events/day)
More DataMore Data
Crustal thicknessCrustal thickness
Sediment thicknessSediment thickness
longitude (deg.)
lati
tud
e (d
eg.)
U/Th in Japan and near KamiokaU/Th in Japan and near Kamioka
Background Level in KamLAND-IIBackground Level in KamLAND-II
14,11,10C : major background sources
KamLAND-IIKamLAND-IIKamLAND-IIKamLAND-II
Expected Energy Spectrum of Single Events in KamLAND-II
Expected Energy Spectrum of Single Events in KamLAND-II
1111CCCNOCNOpeppep
7Be7Be
3 years data3 years data