Recent Results from KamLAND
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Transcript of Recent Results from KamLAND
Recent Results from Recent Results from KamLANDKamLAND
R. D. McKeownCaltechBNL – January 17, 2006
Outline
• Historical Introduction
Neutrino physics
Neutrino mixing and oscillations
• KamLAND reactor neutrino results
• Geoneutrinos
• Future prospects
Discovery of the Neutrino – 1956
F. Reines, Nobel Lecture, 1995
Subsequent History
• 60’s and 70’s – became the darling of accelerator-based particle physics
e ≠
• 1968 – 1st solar anomaly evidence• 1980’s – new interest in neutrino
oscillations (F. Reines, …..)
• 1980-present: the quest for neutrino oscillations
• 1998 – evidence from Super-K
Super-Kamiokande Results
Two Generation Model
1.24
(Pe minimum)
Missing solar neutrinos…
Matter Enhanced Oscillation (MSW)Mikheyev, Smirnov, Wolfenstein
Maki – Nakagawa – Sakata Matrix
CP violation
Pre – KamLAND summary
• Persistent observations of deficit of solar neutrinos
• 1998 – observation of oscillations of atmospheric neutrinos by Super-K
• 2002 – SNO results imply matter-dependent oscillations of solar neutrinos
Time to get our feet on the ground!!
W.A. Fowler Nobel Lecture,
1983
We need a “laboratory”Experiment!!
Enter
• Long Baseline (180 km)• Calibrated source(s)• Large detector (1 kton)• Deep underground (2700 mwe)
Neutrino Oscillation Studies with Nuclear Reactors
• e from n-rich fission products• detection via inverse beta decay (e+pe++n)• Measure flux and energy spectrum• Improve detectors, reduce background• Variety of distances L= 10-1000 m
Detection Signal
Coincidence signal: detect• Prompt: e+ annihilation EEprompt+En+0.8 MeV• Delayed: n capture 180 s capture time
p+e
511keV
511keV 2.2 MeV
d
n
~ 200 MeV per fission
~ 6 e per fission
~ 2 x 1020 e/GWth-sec
Reactor Isotopes
The Reactor Neutrino
Flux and Spectrum• 235U, 239Pu, 241Pu from measurements • 238U calculated• Time dependence due to fuel cycle
Precise Measurements
Flux and Energy Spectrum ~1-2 %
Reactors are calibrated sources of ’s !!
Negative Oscillation Searches
103
Distance (m)
The BIG picture: (From PDG)
SK atm ()
KamLAND usesthe entire Japanese
nuclear powerindustry as a
long baseline source
Kashiwazaki
Takahama
Ohi
Many reactors contribute to the antineutrino flux at KamLANDMany reactors contribute to the antineutrino flux at KamLAND**EEνν>3.4MeV >3.4MeV (E(Epromptprompt>2.6MeV)>2.6MeV)SiteSite Dist Dist
(km)(km)Cores Cores
(#)(#)
PPthermtherm
(GW)(GW)
FluxFlux
(cm(cm-2 -2 ss-1-1))
Rate Rate nooscnoosc**
(yr(yr-1-1 kt kt-1-1))Japan
Japan
KashiwazakiKashiwazaki 160160 77 24.324.3 4.1·104.1·1055 254.0254.0OhiOhi 179179 44 13.713.7 1.9·101.9·1055 114.3114.3TakahamaTakahama 191191 44 10.210.2 1.2·101.2·1055 74.374.3TsurugaTsuruga 138138 22 4.54.5 1.0·101.0·1055 62.562.5HamaokaHamaoka 214214 44 10.610.6 1.0·101.0·1055 62.062.0MihamaMihama 146146 33 4.94.9 1.0·101.0·1055 62.062.0SikaSika 8888 11 1.61.6 9.0·109.0·1044 55.255.2Fukushima1Fukushima1 349349 66 14.214.2 5.1·105.1·1044 31.131.1Fukushima2Fukushima2 345345 44 13.213.2 4.8·104.8·1044 29.529.5Tokai2Tokai2 295295 11 3.33.3 1.6·101.6·1044 10.110.1OnagawaOnagawa 431431 33 6.56.5 1.5·101.5·1044 9.39.3SimaneSimane 401401 22 3.83.8 1.0·101.0·1044 6.36.3IkataIkata 561561 33 6.06.0 8.3·108.3·1033 5.15.1GenkaiGenkai 755755 44 10.110.1 7.8·107.8·1033 4.84.8SendaiSendai 830830 22 5.35.3 3.4·103.4·1033 2.12.1TomariTomari 783783 22 3.33.3 2.3·102.3·1033 1.41.4S
outh
Kore
aSouth
Kore
a
UlchinUlchin 712712 44 11.511.5 9.9·109.9·1033 6.16.1
YonggwangYonggwang 986986 66 17.417.4 7.8·107.8·1033 4.84.8
KoriKori 735735 44 9.29.2 7.5·107.5·1033 4.64.6
WolsongWolsong 709709 44 8.28.2 7.1·107.1·1033 4.34.3
Total Total NominalNominal -- 7070 181.181.
771.3·101.3·1066 803.8803.8
Deta
iled
pow
er
an
d f
uel
Deta
iled
pow
er
an
d f
uel
Com
posit
ion
calc
ula
tion
used
Com
posit
ion
calc
ula
tion
used
From electrical From electrical powerpower
Japanese averageJapanese averagefuel usedfuel used
A limited range of baselines contribute to the fluxA limited range of baselines contribute to the fluxof reactor antineutrinos at Kamiokaof reactor antineutrinos at Kamioka
Korean reactorsKorean reactors3.4±0.3%3.4±0.3%
Rest of the worldRest of the world+JP research reactors+JP research reactors
1.1±0.5%1.1±0.5%
Japanese spent fuelJapanese spent fuel0.04±0.02%0.04±0.02%
Spectrum Distortion
Front End Electronics
Samples (~1.5ns)
AD
C c
ount
s (~
120
V)
Blue: raw datared: pedestalgreen: pedestal subtracted
Waveforms are recorded using Analog Transient Waveform Digitizers (ATWDs), allowing multi p.e. resolution
The ATWDs are self launching
with a threshold ~1/3 p.e. Each PMT is connected to 2
ATWDs, reducing deadtime Each ATWD has 3 gains (20,
4, 0.5), allowing a dynamic range
of ~1mV to ~1V
The KamLAND Collaboration
KamLAND:timelineKamLAND:timeline
•Summer 2000 PMT installationSummer 2000 PMT installation•Jun-Sept 2001 Fill Liquid ScintillatorJun-Sept 2001 Fill Liquid Scintillator•Jan, 2002 Begin Data TakingJan, 2002 Begin Data Taking• Dec, 2002Dec, 2002 Report 1st Physics Results Report 1st Physics Results• Jun 2004Jun 2004 Report 2nd Reactor Report 2nd Reactor Results Results• Sept 2005Sept 2005 Report geoneutrino evidenceReport geoneutrino evidence
Energy Determination & Resolution
E/E ~ 6.2% /√E , Light Yield ~ 300p.e./MeV
Esyst = 2.0% at 2.6 MeV
Tagged cosmogenics can be used for calibrationTagged cosmogenics can be used for calibration
1212BB
1212NN
Fit to data shows that12B:12N ~ 100:1
τ=29.1msQ=13.4MeV
τ=15.9msQ=17.3MeV
μ
Energy calibration uses discrete Energy calibration uses discrete γγ and and 1212B/B/1212NN
68Ge
65Zn
60Co
n-p
Carefully include Birks law, Cherenkov and light absorption/opticsCarefully include Birks law, Cherenkov and light absorption/opticsto obtain constants for to obtain constants for γγ and and ee–type depositions–type depositions
n-12C
σσ/E ~ 6.2% at 1MeV/E ~ 6.2% at 1MeV
z
Vertexing is performed using timing from the 17” PMTsVertexing is performed using timing from the 17” PMTs
-65 (1.1MeV)
-68 (1.0MeV)
-60 (2.6MeV)Am/Be(~8MeV)
neutronsneutrons
Fraction of volume Fraction of volume insideinside the fiducial radius verified the fiducial radius verifiedusing using μμ-produced -produced 1212B/B/1212N and n (assumed uniform)N and n (assumed uniform)
1212B/B/1212NN
Estimate of total volume and fiducial fractionEstimate of total volume and fiducial fraction
Singles Background
14C:? 210Pb: 102Hz:--
85Kr: 606 Hz:--
40K:1.9Hz:2.1Hz208Tl: 3.2Hz:1.4Hz
232Th, cosmogenic: 0.19Hz
High Energy (e.g. μ): 0.33Hz:0.33Hz
Source:Measured:Predicted
Radioactivity inside Liquid Scintillator
- R- Rprompt, delayedprompt, delayed < 5.5 m < 5.5 m
- - ΔΔRRe-ne-n < 2 m < 2 m
- 0.5 - 0.5 μμs < s < ΔΔTTe-ne-n < 1 ms < 1 ms
- 1.8 MeV < E1.8 MeV < Edelayeddelayed < 2.6 MeV < 2.6 MeV
- 2.6 MeV < E2.6 MeV < Epromptprompt < 8.5 MeV < 8.5 MeV
Tagging efficiency 89.8%Tagging efficiency 89.8%
… …In addition:In addition:
- 2s veto for showering/bad 2s veto for showering/bad μμ
- 2s veto in a R = 3m tube along track2s veto in a R = 3m tube along track
Dead-time 9.7%Dead-time 9.7%
Selecting antineutrinos, ESelecting antineutrinos, Epromptprompt>2.6MeV>2.6MeV
(543.7 ton)(543.7 ton)
5.5 m5.5 mfiducial cutfiducial cut
Balloon edgeBalloon edge
Observed Event Rates
2002-4 dataset 766.3 ton•yr, Eprompt > 2.6 MeV
Observed: 258 events
No-oscillation: 365.2 ± 23.7 events
Background 17.6 ± 7.2 events accidental 2.69 ± 0.02 9Li/8He (, n) 4.8 ± 0.9 fast neutron < 0.89 13C(,n) 10.0 ± 7.1
99.998% CL
Nobs – NBG
Nno-osc
= 0.658 ± 0.044 (stat) ± 0.047 (syst)
99.998 % C.L.
Evidence for Reactor e Disappearance!!
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
Ratio of Measured and Expected e Flux from Reactor Neutrino Experiments
Solar : m2 = 5.5x10-5 eV2
sin2 2 = 0.833
G.Fogli et al., PR D66, 010001-406,(2002)
Oscillation Effect
Time Variations of Reactor Power and
Signals
Correlation with reactor power variation
KamLAND best fit : m2 = 7.9 x 10-5 eV2
tan2= 0.45
• Neutrino Mixing• Neutrino Masses• Flavor Oscillations
+
Combined fit with solar neutrino data
m2=7.9+0.6-0.5x10-5 eV2
tan2=0.40+0.10-0.07
Open circles: combined best fitClosed circles: experimental data
Solar Neutrino Results
Geoneutrinos – the early history
More recent references
Geoneutrinos
• U/Th/K in crust/mantle- amount of activity- distribution
• Energy budget – heat generation- plate tectonics- magnetic field
• Structure of earth’s core- constrain models- georeactor?
Inside the Earth
Region Thickness (km )
Continental crust 38 (20 – 70)
Oceanic crust 6-8
Upper Mantle 600
Lower Mantle 2300
Core 3500
U/Th Distribution
Geoneutrino spectrum
The predicted sources of geoneutrinos
KamLAND Data
UTh
Reactor
13C(,n)
Randoms
Confidence Intervals
The press was interesting…
Hindustan Times, August 8, 2005
And finally:
KamLAND Future
• Precision Reactor Neutrino Measurements- 4calibration system- refine analysis methods- more statistics
•Supernova detection• Precision Solar Neutrino Measurements
- radiopurity- low energy threshold
• More precise geoneutrino measurement
Neutrino-proton elastic scattering
e e
, ,,