KamLAND [Kamioka Liquid Scintillator Anti-Neutrino Detector] Reactor Neutrinos & Recent Results Junpei Shirai Research Center for Neutrino Science, Tohoku University (for the KamLAND Collaboration) Apr.17, 2004, Carolina Neutrino of South Carolina

Expected neutrino spectra from various sources 10MeV The spectra steeply increases below ~10MeV and dominated by fluxes from reactors, earth, sun, etc. 10  It is very important to measure low energy neutrinos. We can learn a lot not only on fundamental properties but on generating mechanism of the neutrino! K.Nakamura et al.

Physics of KamLAND 1000ton liq. Scintillator to detect low energy  Reactor Geo Solar Supernova Relic Particle physics Geo-physics Solar physics Astrophysics KamLAND

Challenge to the Solar N  P  Cl(Homestake): 37 Cl   37 Ar e  Significant deficit of   than expected! [SNP] H 2 O(Kamiokande) [real time; 8 B- ] Ga(Gallex/Sage/Gno): for pp- H 2 O(SuperK) [real time; 8 B- ] D 2 O(SNO) [real time; 8 B- ] *    :  m 2 ≠0  d  e  pp [CC] x d  x np [NC] Conclusive evidence for flavor change;   x. The results are well explained by oscillation with MSW-scheme, the LMA solution is the most promising one. x e  x e [ES] KamLAND Reactor experiments  e <   SSM],  -tot =   SSM],   S] consistent with   SSM] 4p+2e   4 He+2  +26.7MeV  E 71 Ga   71 Ge e  x e  x e [ES] ‘60s ‘80s ‘90s ‘00s ‘50~ Other decisive experiment is needed! No evidence for -disappearance Before KamLAND!

KamLAND makes a challenge to SNP by Reactor Neutrino Experiment n+A  X+Y+2n+Q th (~200MeV) 235 U, 239 Pu, 238 U, 241 Pu n-rich   decay  ~6 e =185km 70GW; ~6% of world’s reactor power KamLAND P( e  e )  2 [  M 2 L/4E] P( e  e )=1  sin 2 2   M 2 ~10  5 eV 2 [LMA] Reactor: Pure e source Distant from Kamioka(km) 100 Detector: Event rate/yr/kt 1000ton LS target *Commercial power reactor (3GW th ): 5.   e /s! (L~100km)

Previous reactor results No -deficit up to 1km Goesgen: Excellent agreement with expectation KamLAND Reactor power  Target Mass (MW*ton)  m 2 sensitivity (eV 2 ) Fit without oscillation Derived independently from  -spectroscopy First to reach 10  eV 2. Positron Energy Events/MeV/hr

KamLAND Collaboration

2.2km Location of KamLAND Gifu 400km Kamioka Underground Lab.(KamLAND) Toyama

KamLAND area Control room Rn-free gas system Detector Water purification system 2.2km 1km To the mine entrance SuperK Oil purification system Mt.Ikenoyama

KamLAND Detector 1000m rock (=2700m water equivalent)    rate:~0.34Hz, 10   earth level LS 20m 13m LS: PC(20%)+n-dodecane(80%) +PPO(1.52g/l); 1000ton Plastic balloon (3nylon+2EVOH film, 135  m thick; Rn-barrier) Buffer oil (iso+n-dodecane, 2.5mthick) PMT: 1325(17”)+ 554(20”),  Outer Detector Pure water(3.2kton) PMT: 20”(225) Inner Detector Shield against fast n,  from rocks, Water Cherenkov detector to identify cosmic  ’s Calibration device Stainless-steel spherical tank (18m  )

PMT assemble & installation Kamioka Sendai In the detector tank Completed! (Sep.’00) (‘99~’00)

Balloon development 1/4-scale model Real-size model (‘97~’99) Water test in KamLAND 4 proto types, 3 1/4-scale and 1 real size models were tested before the final version! Proto-type

Looking up the balloon. Balloon installation Final version Pulling up! Detector tank (Dec.’00-Mar.’01) Kamioka

Taking measure against Rn. Eval lining in the tanks. Insert nylon pipes into the stainless steel pipes. Cleaning every parts by water, detergent, chemical,… Cleaning the purification system ~2001

Mineral oil delivery To detector Monitor the balloon in the detector Simultaneous water filling in the anti-counter Prepare and purify LS & MO Water extraction (K, U,Th) N 2 purge (O 2, H 2 O) May.-Oct., ‘01. Oil filling

First light of KamLAND ! Nov.26, 2001 Clipping  -on

e detection e + p  e + + n [  1.8MeV] e+ee+e 2  (0.51MeV) np  d+  (2.2MeV) TeTe Prompt =E  0.8MeV Delayed neutron-ID Only e. Prompt-Delayed combination (  ,  T) and delayed capture energy for neutron-ID significantly reduces backgrounds ! Cross section: large ~100  ( e  e) and precisely known (0.1%).  ~210  s Inverse  decay:

Front Electronics

e flux calculation from reactor information Thermal power Burnup 235 U 239 Pu 238 U 239 Pu Total Wakasa Bay Kashiwazaki Others Reactor flux Neutrino spectra of fuel elements/fission Fission rate  (E ) reactors

Vertex distribution at different energy region. Stopping  Unstable nuclei produced by  ’s 214 Bi in the balloon External       ’s from 40 K in the balloon Radio-impurities in the liq. scintillator Balloon Fid.vol(R<5m) Balloon Fid.vol(R<5m) Fiducial volume cut rejects backgrounds near the balloon. Requiring delayed neutron rejects most of backgrounds in the fiducial volume except for neutron emitters ( 8 He/ 9 Li), fast neutrons and a part of events below 1 MeV which are carefully analyzed.

Radio-impurity check by 214 Bi- 214 Po chains      spectrum Po   b   spectrum  T of delayed  ’s  (Po)=237  s) Vertex position of delayed  Fid.vol. cut Fid.volume Thermo- meter & a string 214 Bi 214 Po 210 Pb      =237  s

U; 214 Bi  214 Po Th; 212 Bi  212 Po U/Th concentrations from Bi-Po decays (Mar.’02 -Oct.‘02)  Bq/m  Bq/m 3 U: (3.5±0.5)  10  18 g/g Th: (5.2±0.8)  10  17 g/g U/Th series in KamLAND LS highly clears 1  Bq/m 3, which is required for planned 7 Be solar neutrino detection ! << 1  Bq/m 3 7 months (Mar.~Sep.,’02) 1  Bq/m 3 (Assuming radio-equilibrium) Highest level of radio-purities in the world !!

Energy calibration Sys. error  ray sources 68 Ge(2 .511), 65 Zn(1.116), 60 Co( ), Am/Be (7.652); along the central vertical axis (z axis). Neutron captures after spallation events ; np    (2.225), n 12 C  13 C  (4.947); 4  Time dependence: 0.6% position dependence: 1.4%, linearity: 1.1%  E sys 2.1% for  N ev. Systematic error Fractional difference of reconstructed and the known energies of  -ray sources

11 [N ev,obs /N ev,calc ] [N Tot,obs /N Tot,calc ] =±   N ev /N ev  Non z-axis; by spallation neutrons Position resolution  =25cm 60 Co  -ray sources along the Z-axis Position calibration Uncertainty of the event number in the fiducial volume;

Energy spectrum of single ionization events 85 Kr Observed spectrum is well understood by U/Th, spallation events and backgrounds.

 Most unstable products  -decays, and they are rejected by requiring delayed neutron. Non-showering  -on; Neutron emitters ( 8 He& 9 Li) are rejected by time/space cuts.  “Showering  -on” (extra charge  Q>10 6 p.e.~3GeV): 2s veto of total volume. Veto 2s & 3m within the  -on track. Dead time; 11.4% Li/He: 0.94±0.85 events (in the sample of first Results, 0.  kt  year) Rejection of  -on induced backgrounds Study of fast neutron background Balloon Fid. vol. R of the prompt events tagged by only the outer detector <0.5events veto n  n 

Event selection for reactor e events: Prompt; E prompt >2.6MeV [remove geo- ] Delayed;   ay =(1.8  2.6)MeV  R<160cm  T=(0.5  660)  s Fiducial vol.; R<5m >1.2m from z-axis. E delay vs.  R E delay vs.  T 660  s 160cm [Before E prompt cut] E prompt vs. E delay neutron-captured by 12 C [Data sample:0.162kton  yr from 145.1d of Mar-Oct,’02] Observed: 54 events (~1 background from 9 Li/ 8 He and fast neutrons) Expected (with no-oscillation): (86.8±5.6) events 2.6MeV

Positron spectra and rate R(obs/ no- oscill.)=0.611±0.085(stat)±0.041(sys) (E e+ >2.6MeV) First observation of reactor e deficit (99.95%CL). 2.6MeV KamLAND Assuming CPT invariance -oscillation is the dominant process to SNP. 1km ~180km (Other mechanisms like SFP(spin-flavor precession) due to  and -decay are not the leading mechanism to the SNP.)

Allowed & excluded oscillation regions by KamLAND and other experiments [Rate only] By assuming CPT invariance all solutions to the SNP other than LMA is excluded. A part of LMA is also excluded. [Rate+Shape] LMA is further restricted to two narrow regions in  m 2. Including E prompt >0.9MeV data with a free parameter for geo- does not change a lot. Geo- events; 4( 238 U) and 5( 232 Th) are obtained (~40TW), while radio- genic power 0~110TW are

KamLAND continues data taking ! Fraction of the physics run time/week Aug.’03 Mar.’04 80% 100% Detector is quite stable; 2 years data have been accumulated since Mar.’02. 7 months

Prospects of KamLAND. Higher statistics requires less systematic error (6.4% now). studies on energy scale, improved vertex position 4π calibration device 3% 95%CL allowed by 5-year data 2 bands in LMA can become narrower and discriminated by ~10  5% It will be reduced by;

Another oscillation search by a new reactor (Shika-2) joining in 2006 ! 3.926GW th at 88km from KamLAND(Oscill. Minimum). 25% increase of  at KamLAND. Expected contribution of Shika-2 by 3-year data sample No oscill. LMA1: 45±37.26±.21 LMA2: 121±36.70±.21 No oscill. 173 R(exptd/no osc.) KamLAND 1km 100km No of events (>2.6MeV) 2.6MeV

Solar e search by KamLAND which may make a contribution to SNP. [PRL92,071301(2004)] e e 1) Majorana (  )   suggests possible magnetic moment and neutrino decay Transition  (  0)  B T (Solar Mag.Field): e   + Flavor oscillation :   e 2) decay: | e >=cos  | 1 >+sin  | 2 >  1 +J[Majoron] cos  | e >  sin  |  > KamLAND has a source-independent sensitivity to e. If we take a search region, E = MeV, dominant flux of 8 B solar can be used for the studies on e  e transition. Reactor, atmospheric, WIMPs, relic are expected to be small, <0.1 events/kt  year.

Data sample: live-days in ’02, 0.28kton  year (  0.162kton  year:first results) Correlated events ( e p  e + n) with E e + = MeV, R fid.vol <550cm (  500cm) *Bkg..2 .2 (reactor).001(atmosph.).3 .2(fast n).002 (accidental).6 .2( 8 He/ 9 Li)  Sys. Error 6.3%  : 1.6%  :.2 n p  f v : 4.3 E th : 4.5 livetime:.07 No e signal !   <370cm -2 s -1 (90%CL) <2.8   SSM [( )MeV] 30 times improves the previous best limit by SuperK [PRL90,171302(‘03)] Prompt E e+ Delayed E Search region for solar e  /10  10  B ]  [B T /100kG]<1.3  2 /m 2 >0.067s/eV The results constrain models of  and lifetime. (  <   10  B by MUNU,PLB553,7(2003))

Challenge to Geo- detection Radiogenic heat generation: How much? It is the basic factor in the interior dynamics and evolution of the earth, but not well known. It is dominated by 238 U and 232 Th decays, and expected to ~16TW, but is model dependent and no direct measurement to date. KamLAND can measure the flux and spectrum (>1.8MeV) of geo- e ; 5   -decays with Q   1.8MeV are observed; 238 U: 234 Pa  U, 214 Bi  Po, 232 Th: 228 Ac  Th, 212 Bi  Po, 208 Tl  Pb ~60 e events/kt/yr U/Th ratio New approach to geo-physics will be opened by KamLAND !!

Challenge to 7 Be solar by KamLAND New real-time measurement of solar other than 8 B-. High Intensity;        (7.3% of the total) Next to the pp- flux, ~940    B] Low Energy and monochromatic; 862keV(90%), 384keV(10%) from 7 Be e   7 Li  (  ) Spectrum: “Compton edge (665keV)” of 862keV Seasonal variation: ~7% (min./max.) High statistics :   /kton  year [LMA] KamLAND: recoil electron of e  e (T e  280keV; 14 C   decay)

Significance of the flux measurement is increased if uncertainty of the SSM prediction (±10%) is reduced by better understanding of the burning mechanism of the sun ! Direct check of LMA, Mixing parameter measurement, CPT check with reactor results Search for  d  /dT=(d  /dT) Weak +(d  /dT) EM Lower E and T e makes sensitive to the contribution of EM term from .  2 (  2 /m e 2 )(1/T e -1/E ) Sensitivity to  by 1.5kt  yr LMA Backgr. subtracted  f    Sys.:3% EM:  SSM *0.99      (90%CL)  

Future goal ! 85 Kr Present status

Challenging 7 Be solar New purification System to remove; 218 Po  214 Pb  Bi  Po  210 Pb 85 Kr (t 1/2 ; 10.8yr) ~1Bq/m Pb (t 1/2 ; 22.3yr) ~0.1Bq/m 3 85 Kr, 210 Pb Goal: 1  Bq/m 3 85 Kr  85 Rb   (  687keV) 210 Pb  210 Bi  210 Po  206 Pb ~1hr 222 Rn (t 1/2 ; 3.8d)   (  1163)  (5304) R&D’s are underway! New nitrogen purge, Filtration,adsorption,distillation,etc. [Present system] Water extraction N 2 purge

Conclusion KamLAND with a 1000ton ultra-pure liq.scintillator is challenging to low energy physics; First observation of reactor disappearance (challenge to LMA); Strongly supports oscillation, Excludes all solutions to SNP except for LMA (by rate), Restricts oscillation parameters (rate+shape). Higher statistics of reactor data is being analyzed to find spectrum distortion which will be another evidence for neutrino oscillation and further restrict the parameter region. New results on e above the reactor energy region provides improved limits on [trans.-   solar B T ] and -lifetime. Detection of geo- ; first results will come out soon and it would open up a new field of “ -geophysics”.

7 Be solar   ; KamLAND has made R&Ds to realize the challenging measurement. Direct confirmation of LMA and precise measurement of the flux could contribute a lot to determination of the oscillation parameters and better understanding of the burning mechanism of the sun.