KamLAND : Studying Neutrinos from Reactor Atsuto Suzuki KamLAND Collaboration KEK : High Energy Accelerator Research Organization

OutlineOutline 1. KamLAND Overview 2. Reactor Neutrinos 3. e Detection in Liquid Scintillator 4. Reactor Neutrino Event Rate 5. Oscillation Analysis 6. One More Nuclear Reactor 7. Conclusions

HistoryHistory October 1994 : KamLAND proposal October 1997 : Full budget (~ 25 M$) by JSPS April 1998 : Construction of detector & underground facility October 1999 : US-KamLAND proposal was approved by DOE January 22, 2002 : KamLAND launched data-taking June 2004 : 7 Be solar neutrino budget by JSPS (~ 6 M$ / 5 yrs) June 2005 : KamLAND operation and upgrade by MEXT (~ 20 M$ / 5 yrs) August 2009 : New budget proposal (Xe  decay in KamLAND) will send to the government 1. KamLAND Overview

13 m 18 mpresent KamLAND Detector LS (Gd) LS (Xe) original design water : Kamiokande 1000 ton liquid scintillator : 80% (dodecane) + 20% (pseudocumene) g/l PPO : housed in spherical plastic balloon inch inch PMT’s

KamLANDPhysicsGoalsKamLANDPhysicsGoals PRL 80 (1998) 635 e e Geo 7 Be CNO pep 3 years data background subtracted e e Solar m2m2 sin 2 2  e e reactor > 100 km long baseline

Kamioka 70 GW (~12 % of global nuclear power) 70 GW (~12 % of global nuclear power) Nuclear reactors : very intensive sources of e Kashiwazaki power station : 24.3 GW 55 commercial nuclear power reactors : nominal output ~155 GW 2. Reactor Neutrinos Korean reactors : 3.2 % (World + Research) reactors : 0.96 % reactors : 0.96 % at L ~ (175 ± 35) km at L ~ (175 ± 35) km effective baseline : ~ 180 km

Reactor Records from Power Companies Thermal Power 2002 thermal power generation, fuel burn-up, fuel exchange and enrichment thermal power generation, fuel burn-up, fuel exchange and enrichment 99.9% of e from 235,238 U and 239,241 Pu

235 U 239 Pu 238 U 241 Pu March 9, 2002 – January 11, 2004 Fission Yields & e Energy Spectrum Fission yields for 4 fissile elements Reactor neutrino energy spectrum at Kamioka

Reactor Operation Histories KL1 1 st result : March 2002 ～ October 2002, PRL. 92, (2003) “Evidence for Reactor Antineutrino Disappearance ” KL1 KL2 2 nd result : March 2002 ～ January 2004, PRL. 94, (2005) “Evidence for Spectral Distortion” KL2 KL3 3 rd result : March 2002 ～ May 2007, PRL. 100, (2008) “Evidence for Neutrino Oscillation Cycle” KL3 Many reactor inspections Steam pipe rupture New nearby reactor being turned on and off Big earthquake “Experimental Investigation of Geoneutrinos”, Nature 436, 400 (2005)

3. e Detection in LS E th = 1.8 MeV E prompt (e + ) = E  MeV Distinct 2-step signature : prompt : e + ionization, annihilation prompt : e + ionization, annihilation delayed :  from thermal neutron capture on p capture on p or on 12 C or on 12 C (  : 4.9 MeV) E delayed (  ) = 2.2 MeV,  t ~ 200  s ν e +p→n+e + cross section ν e +p→n+e + cross section E v (MeV) ~

Systematic% Fiducial volume 4.7 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 Detection at KL1 Systematic Errors for Reactor Neutrino Detection at KL1  n 12 N, 12 B,…  radioactive sources, laser system, LEDs, cosmic-ray ,  –induced spallation products

reconstructed energy deviation[%] R(cm) reconstructed position deviation[cm] R(cm) 4.7 % (KL1) Full Volume Calibration R<5.5 m

Dominant Background Source : 13 C( ,n) 16 O Annihilation  (1 st excited state) Neutron capture on 12 C Proton recoil (ground state)  (2 nd excited state)

Measurement of Quenching for Proton Signals in LS Osaka Univ.

Summary of Updated Systematic Uncertainty Total systematic error : 6.4 % >>> 4.1 % Total systematic error : 6.4 % >>> 4.1 % Fiducial volume : R = 5.0 m >>> 6.0 m Energy threshold : 2.6 MeV >>> 0.9 MeV Improved 13 C( ,n) 16 O background estimation Fiducial volume : R = 5.0 m >>> 6.0 m Energy threshold : 2.6 MeV >>> 0.9 MeV Improved 13 C( ,n) 16 O background estimation Other improvements from KL1 (4.7) (2.3)

4. Reactor Neutrino Analysis : Event Rate 4. Reactor Neutrino Analysis : Event Rate

Event Selection in KL3 prompt delayed X 2 + y 2 [m 2 ] Z [m] E prompt (MeV) E delayed (MeV)

KL1 KL2 KL3 Exposure (tonyr) Observed ev (E prompt : MeV) (>2.6) (>2.6) (>0.9) Expected ev.86.8 ± ± ± 89 Background ev ± ± ± 23.5 accidental ± ± 0.02 ± Li/ 8 He ( , n) 0.94 ± ± ± 1.0 fast neutron 0 ± 0.5 < 0.89 < C( , n) 16 O gs, 1st, 2nd 10.3 ± ± 17.7 # of Observed and Expected Events (N obs –N back ) / N expect (±stat ±syst) ±0.085±0.041 ±0.044±0.047 ±0.020± % CL % CL 8.5 

LMA:  m 2 = 5.5x10 -5 eV 2 sin 2 2  = LMA:  m 2 = 5.5x10 -5 eV 2 sin 2 2  = Ratio = (N obs – N back ) / N expect Ratio KL1 KL2 KL3

5. Oscillation Analysis

KL2 2-Flavor Analysis KL1 solar

Fit to scaled no-oscillation spectrum : exclude at 5.1  KL3 tan 2  =  m 2  = 7.58 x eV

KL1 KL2KL3 tan 2  =  m 2  = 7.59 x eV KamLAND + Solar tan 2  =  m 2  = 7.58 x eV KamLAND

3-Flavor Oscillation Analysis best fit KamLAND tan 2  =  m 2  = 7.58 x eV

KL2 Neutrino Oscillation Cycle effective : 180 km KL3

L o /E Oscillatory Shape : L o = 180 km KL3 L/

6. One More Nuclear Reactor Natural Nuclear Reactor at the Earth Center

28 Natural nuclear reactor in the center of the Earth was proposed in 2001 as the energy source of geo-magnetic field. Not a mainstream theory, but not ruled out by any evidence. Explains mechanism for flips of the geo- magnetic field. Geo-Reactor

Signature from Geo-Reactor Y-intercept : Geo-Reactor + BG theoretical prediction : 3 TW big earthquake Kashiwazaki power station : 24.3 GW

7. Conclusions disappearance oscillation cycle precise measurement of oscillation parameters

Next Step : 7 Be CNO pep Solar Neutrino Detection