Antineutrino Physics in KamLAND Atsuto Suzuki 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, 2007

KamLAND: 3 rd Generation Experiment at Kamioka 3 rd generation KamLAND: 1000 ton Liquid Scintillator Detector 2 nd generation Super-Kamiokande: 50,000 ton Water Cerenkov Detector (1996 ~ ) 1994: proposal 1997: Budget was approved. Construction started. Construction started. 1999: Japan-US collaboration 2002: Data-taking started. History 1 st generation Kamiokande: 3000 ton Water Cerenkov Detector ( )

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) g/l PPO : housed in spherical plastic balloon 1325x17-inch + 554x20-inch PMT’s photocathode coverage : 34% energy resolution : 6.2 %/ ( E:MeV) 1/ m 3 stainless steel vessel KamLAND Detector : filled with a mixture of paraffin oil and dodecane (  = 0.04%)

inner view of spherical vessel

180 km KamLAND Experiment Kamioka Liquid scintillator AntiNeutrino Detector 1000 ton liquid scintillator detector 7 Be, CNO+pep

KamLAND Data Samples for Outcomes Mar. 9, 2002 – Oct. 30, 2004 (live time = days) Mar. 4 – Oct. 6, 2002 (live time = days) Mar. 9, 2002 – Jan. 11, 2004 (live time = days) physics run calibration run test/bad run 1 st reactor result : Evidence for Reactor Antineutrino Disappearance 2 nd reactor result : Evidence of Spectral Distortion 1 st geoneutrino result : Experimental Investigation of Geologically Produced Antineutrinos

Nuclear Power-Stations around Kamioka Kamiok a Kashiwazaki : world biggest power station (24.3 GW) 70 GW (~7 % of world total power generation) at L ~ (175 ± 35) km 70 GW (~7 % of world total power generation) at L ~ (175 ± 35) km huge power nearly equal distance long baseline (180 km) ⇩ Kamioka : suitable location for neutrino oscillation study huge power nearly equal distance long baseline (180 km) ⇩ Kamioka : suitable location for neutrino oscillation study commercial reactors : 53 nominal power output : 152 GW in Japan

distance from Kamioka (km) no. of neutrinos  ８６％：（１７５ ± ３５）ｋｍ  ９７％： Japanese stations  2.2 ％： Korean 〃 〃  0.2 ％： European 〃 〃  0.12 ％： Taiwanese 〃 〃  0.12 ％： North American 〃 ReactorContribution at Kamioka Reactor e Contribution at Kamioka

e ~210  s How to Detect e in Liquid Scintillator inverse  – decay : p  (2.2 MeV) n e+e+ d delayed coincidence method : prompt e + + delayed  (2.2 MeV) e + p  e + + n e + p  e + + n E ~ E e MeV E th = 1.8 MeV high rejection-power for background events prompt signal delayed signal

2.6 MeV <E prompt < 8.5 MeV 1.8 MeV <E delayed < 2.6 MeV Expect 1.5 n- 12 C captures Accidentalbackground geoneutrino region 2.6 MeV Prompt vs. Delayed Energy for e Candidate Events

expected （ no oscillation) observed Evidence for Reactor e Disappearance exposure tonyr observed ev. 258 expected ev. 365 ± 24 background ev ± 7.3 (N obs – N BG )/N expected = ± (stat) ± (syst) disappearance with % CL Time Dependence of Event Rate

Evidence of Reactor e Spectral Distortion Null Shape-Distortion excluded at 99.8 % CL 2-Flavor Oscillation Fit best fit with rate + spectrum shape  m 2 (eV 2 ) = 7.9 x sin 2 2  = 0.98 un-binned likelihood fit :    d.o.f. = 24.2/17 best fit with rate + spectrum shape  m 2 (eV 2 ) = 7.9 x sin 2 2  = 0.98 un-binned likelihood fit :    d.o.f. = 24.2/

allowed LMA-II LMA-I LMA-0 allowed  m 2 = 8.0 x eV 2, sin 2 2  = 0.98 Constraints on Oscillation Parameters disfavored at 97.5% C.L. disfavored at 98.0% C.L. event rate spectral shape + e  x e  xexcluded LMA

Observation of Neutrino Oscillation Pattern (L 0 ≡180 km) evidence of neutrino oscillation at ９９． 8 ％ C.L. !!! evidence of neutrino oscillation at ９９． 8 ％ C.L. !!! N obs / N exp definite baseline (~ 180 km) ⇒ test oscillation hypothesis Δm 2 =7.9x10 -5 eV 2 sin 2 2θ=0.98 L/E (km/MeV)

2-Flavor Oscillations (All Solar + KamLAND) 2-Flavor Oscillations (All Solar + KamLAND) assuming CPT invariance the most precise determination of  m 2 to date the most precise determination of  m 2 to date  m 2 = 7.9 x eV 2 tan 2  = 0.40  m 2 = 7.9 x eV 2 tan 2  = – – 0.07

A. Smirnov, 2002 Solutions to Solar Neutrino Problem KamLAND solved the solar neutrino problem under the laboratory conditions (J. Bahcall) KamLAND solved the solar neutrino problem under the laboratory conditions (J. Bahcall)

U, Th, K decays: radiogenic heat U, Th, K decays: radiogenic heat Experimental Investigation of Geologically Produced Antineutrinos Experimental Investigation of Geologically Produced Antineutrinos e e Heat Generation : basic factor Heat Generation : basic factor Interior Dynamics Formation History geoneutrino detection

Heat Balance between Dissipation and Generation heat dissipation 44 TW or 31 TW mW m-2cooling ~20 TW ??? ~20 TW ??? radiogenic ~20 TW ??? generation new idea : georeactor????????? ≡

U U+Th Number of antineutrinos (1/MeV/decay) Antineutrino 1.8 MeV e Energy Spectra of 238 U, 232 Th and 40 K Decays e Energy Spectra of 238 U, 232 Th and 40 K Decays 238 U  206 Pb He + 6 e e MeV 232 Th  208 Pb He + 4 e e MeV 40 K  40 Ca + e - + e MeV (89.3 %) 40 K + e -  40 Ar + e MeV (10.7 %) 238 U  206 Pb He + 6 e e MeV 232 Th  208 Pb He + 4 e e MeV 40 K  40 Ca + e - + e MeV (89.3 %) 40 K + e -  40 Ar + e MeV (10.7 %)

CoreMantleCrust Sediment Our Reference Earth Model [Th] /[U ] ~ 3.9 outer / inner U: 0, Th: 0 U: 0, Th: 0 outer / inner U: 0, Th: 0 U: 0, Th: 0 (units: ppm) continental U: 2.8, U: 2.8, Th: 10.7 Th: 10.7oceanic U: 1.7, U: 1.7, Th: 6.9 Th: 6.9continental U: 2.8, U: 2.8, Th: 10.7 Th: 10.7oceanic U: 1.7, U: 1.7, Th: 6.9 Th: 6.9 upper / lower U: 0.012, Th: U: 0.012, Th: upper / lower U: 0.012, Th: U: 0.012, Th: upper U: 2.8, Th: 10.7 U: 2.8, Th: 10.7middle U: 1.6, Th: 6.1 U: 1.6, Th: 6.1lower U: 0.2, Th: 1.2 U: 0.2, Th: 1.2upper U: 2.8, Th: 10.7 U: 2.8, Th: 10.7middle U: 1.6, Th: 6.1 U: 1.6, Th: 6.1lower U: 0.2, Th: 1.2 U: 0.2, Th: 1.2 U: 0.10, Th: 0.22

geoneutrino production points observed by KamLAND km Geoneutrino Production in Our Reference Model crust mantle sediment Cumulative Flux (1/cm 2 /sec) cumulative geoneutrino flux (U-chain) (U-chain)~70% ~25% <5%

Antineutrino Energy (MeV) Events/0.17 MeV [U]+[Th] = 19 ev 2.38±0.01 Accidental Coincidence # of events Background 127 ±13 Total best fit 80.4± ±0.2 Reactor e short lived long lived 42 ±11 13 C ( ,n) 16 O Energy Distributions of Candidate & Background Events signal 152 # of geoneutrinos: 25 events

Maximum Likelihood Analysis for Geoneutrino Flux # of U,Th: free parameter,  m 2,sin 2 2  : best fit value±1 , 13 C( ,n) 16 O: peak width & height: free parameter confidence interval for # of detected geoneutrinos (N U – N Th )/(N U + N Th ) N U + N Th best fit CL 68.3% CL 95.4% CL 99.7% Th/U~3.9Th/U~3.9 reference model

First Geoneutrino Results Assuming Th/U~  2 KamLAND observed total number of geoneutrinos: total number of geoneutrinos: U+Th (best fit) : 28 U+Th (best fit) : 28 U+Th (rate analysis) : 25 U+Th (rate analysis) : 25 BSE prediction 1.45x e /(target protonyear) 1.45x e /(target protonyear) 1.62x10 7 cm -2 s -1 at KamLAND 1.62x10 7 cm -2 s -1 at KamLAND 60 TW from our reference model 60 TW from our reference model 99% confidence upper limit of e flux:

Conclusion KamLAND Collaboration (China-France-Japan-US)

13 C ( ,n) 16 O* Correlated Background   source in LS 206 Pb 210 Bi 210 Po 210 Pb d22.3 ystable138.4 d  (long-lived Rn decay product) p 12 C*   (4.4 MeV) prompt 16 O* n p recoil proton +   (6.13 MeV) e + e - (6.05MeV) prompt n delayed  (2.2 MeV) 13 C  + 17 O* ( 1.1% in 12 C) recoil proton

Survived Background Sources Survived Background Sources Background # of events 9 Li/ 8 He 4.8 ±0.9 Accidental Coincidence Coincidence2.69±0.02 Fast Neutron 13 C ( ,n) 16 O* < ±7.1 Total 17.8 ±7.3 Q deposit > 10 6 p.e.  T  < 0.5 s 0.5<  T< 1 ms  R < 2 m  n 9 Li 9 Be 8 Be+n  :178.3 ms 9 Li background rate: 0.03 ev/day

N obs /N no oscillation Ratio of Observed to Expected e Ratio of Observed to Expected e Flux for Reactor Neutrino Experiments KamLAND LMA:  m 2 = 5.5x10 -5 eV 2  m 2 = 5.5x10 -5 eV 2 sin 2 2  = sin 2 2  = 0.833LMA:  m 2 = 5.5x10 -5 eV 2  m 2 = 5.5x10 -5 eV 2 sin 2 2  = sin 2 2  = 0.833

neutrino tomography Future Plan SNO+ Finland KamLAND

e Event Selection ① inverse  - decay selection 2.6 < E prompt < 8.5 MeV 1.8 < E delay <2.6 MeV 0.5 <  T< 1000  s  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 : ton ④ data sample (2 nd result): days exposure time = ton-year prompt delayed

More exotic, non-oscillations models for the antineutrino channel start being less favored by data Decay * excluded at 95% CL * V.Barger et al. Phys. Rev. Lett. 82 (1999) 2640 Decoherence † excluded at 94% CL † E.Lisi et al., Phys. Rev. Lett. 85 (2000) 1166

Geoneutrino Fathers and Grandfather Fathers : G. Eder, Terrestrial Neutrinos, G. Eder, Terrestrial Neutrinos, Nucl. Phys. 78, 657 (1966) Nucl. Phys. 78, 657 (1966) G.Geophysics by Neutrinos, G. Marx, Geophysics by Neutrinos, Grandfather : G. Gamow, Letter to F. Reines (1953) G. Gamow, Letter to F. Reines (1953) Czechoslovak J. Phys. B19, 1471 (1969) J. Phys. B19, 1471 (1969)Czechoslovak

Space and Time Correlations between Prompt and Delayed Events 0.5<  T<500  s 0<  L<100 cm 0.9<E prompt <2.7 MeV TT LL

Systematic% Scintillator volume 2.1 Fiducial fraction 4.2 Energy threshold 2.3 Cuts efficiency 1.6 Live time 0.06 Reactor P thermal 2.1 Fuel composition 1.0 Time lag 0.01 Antineutrino spectrum 2.5 Antineutrino x-section 0.2 Total6.5 Systematic Errors (for reactor neutrino flux) 150  s <  T< 10 ms  L < 3 m 12 B 12 N 12 B 12 N τ=29.1ms Q=13.4MeV τ=15.9ms Q=17.3MeV distribution: uniformly in space uniformly in space

2. Oscillation Studies by Reactor Antineutrinos Reactor Antineutrinos 235 U + n  N 1 + N 2 + xn +6.1   e + (201.8±0.5 MeV) Nuclear reactors are very intense sources of e from Nuclear reactors are very intense sources of e from the  -decays of neutron-rich fragments : the  -decays of neutron-rich fragments : E prompt (e + ) = E  MeV 2-step signature : prompt : e + ionization, annihilation prompt : e + ionization, annihilation delayed : thermal neutron capture on p delayed : thermal neutron capture on p E delayed (  ) = 2.2 MeV,  t ~ 200  s Antineutrinos are detected through inverse  -decay : e + p  e + + n E th = 1.8 MeV 1/3 of total e ’s ν e +p→n+e + cross section ν e +p→n+e + cross section E v (MeV)

13 C( , n) 16 O* (n, p) 12 C(n, n  ) 12 C 13 C( , n) 16 O Expected Energy Expected Energy Spectra of 13 C ( ,n) 16 O*, 16 O Correlated Events Expected Energy Expected Energy Spectra of 13 C ( ,n) 16 O*, 16 O Correlated Events free parameter in likelihood analysis peak height for reactor neutrinos peak height for reactor neutrinos peak height & width for geoneutrinos peak height & width for geoneutrinos reactor geo- geo-

expected (no oscillation) observed Time Dependence of Observed Event Rate 90% CL ···· best fit fit constrained through expected background (0.03 events/day)

More Data Crustal thickness Sediment thickness longitude (deg.) latitude (deg.) U/Th in Japan and near Kamioka

Background Level in KamLAND-II 14,11,10 C : major background sources KamLAND-IIKamLAND-II

Expected Energy Spectrum of Single Events in KamLAND-II Expected Energy Spectrum of Single Events in KamLAND-II 11 C CNO pep 7 Be 3 years data