Reactor Neutrino Experiments Jun Cao Institute of High Energy Physics Lepton-Photon 2007, Daegu, Aug , 2007

2 Outline  Past Reactor Neutrino Experiments  Palo Verde  Chooz  KamLAND  Theta13 experiments  Angra  Daya Bay  Double Chooz  RENO  Search for neutrino magnetic moment  TEXONO  Summary

3 Past Reactor Neutrino Experiments Reactor anti-neutrino experiments have played a critical role in the 50- year-long history of neutrinos.  The first neutrino observation in 1956 by Reines and Cowan.  Determination of the upper limit of mixing angle theta13 to sin 2 2  13 <0.17 (Chooz, Palo Verde)  The first observation of reactor anti-neutrino disappearance at KamLAND in Now reactor neutrino experiments become prominent again for measuring mixing angle  13 precisely.

4 Savannah River Experiment  The first neutrino observation in 1956 by Reines and Cowan.  Inverse beta decay in CdCl 3 water solution  coincidence of prompt and delayed signal  Liquid scintillator + PMTs  Underground  A modern experiment is still quite similar, except  Larger, better detector  Deeper underground, better passive and active shielding  Now we know how to load Gd into liquid scintillator Capture on H, or Gd, Cd, etc. Delayed signal Prompt signal

5 Reactor Neutrino Spectra  235 U, 239 Pu, 241 Pu beta spectra were measured at ILL. 238 U spectrum is calculated theoretically.  Counting rate and spectra were verified by Bugey and Bugey-3  Power fluctuation <1%, counting rate precision ~2% with burn-up evolution.  Spectra precision ~2%  Rate and spectra precision are less important for next theta13 experiments. Peak at 4 MeV

6 CHOOZ Baseline 1.05 km , France 8.5 GWth 300 mwe 5 ton 0.1% Gd-LS Bad Gd-LS ParameterRelative error Reaction cross section1.9 % Number of protons0.8 % Detection efficiency1.5 % Reactor power0.7 % Energy released per fission0.6 % Combined2.7 % R=1.01  2.8%(stat)  2.7%(syst), sin 2 2  13 <0.17 Eur. Phys. J. C27, 331 (2003)

7 Palo Verde , US 11.6 GWth Segmented detector 12 ton 0.1% Gd-LS Shallow overburden 32 mwe Baseline 890m & 750m R=1.01  2.4%(stat)  5.3%(syst) Palo Verde Gd-LS Chooz Gd-LS 1st year 12%, 2nd year 3% 60%/year Phys.Rev.D64, (2001)

8 KamLAND 2002-now, Japan 53 reactors, 80 GWth 1000 ton normal LS 2700 mwe Radioactivity  fiducial cut, Energy threshold Baseline 180 km

9 KamLAND The first observation of reactor anti-neutrino disappearance Confirmed antineutrino disappearance at % CL Excluded neutrino decay at 99.7% CL Excluded decoherence at 94% CL R=0.658  0.044(stat)  0.047(syst) Phys.Rev.Lett. 94, (2005)

10 Neutrino Oscillation Neutrino Mixing: PMNS Matrix Atmospheric, K2K, MINOS, T2K, etc.  23 ~ 45º Solar KamLAND  12 ~ 30º Reactor Accelerator  13 < 12º Known: |  m 2 32 |, sin 2 2  23,  m 2 21, sin 2 2  12 Unkown: sin 2 2  13,  CP, Sign of  m 2 32 “We recommend, as a high priority, …, An expeditiously deployed multi-detector reactor experiment with sensitivity to  e disappearance down to sin 2 2  13 =0.01” ---- APS Neutrino Study, 2004

11 Precisely Measuring theta13 ParameterRelative errorBy Near/far configuration Reaction cross section1.9 %Cancel out Number of protons0.8 %Reduced to ~0.3% Detection efficiency1.5 %Reduced to 0.2~0.6% Reactor power0.7 %Cancel out or reduced to ~0.1% Energy released per fission0.6 %Cancel out Chooz Combined2.7 % Major sources of uncertainties:  Reactor related ~2%  Detector related ~2%  Background subtraction Lessons from past experience:  Need near and far detectors  Chooz: Good Gd-LS  Palo Verde: Go deeper  KamLAND: No fiducial cut, lower threshold 4 MeV

12 Proposals for measuring  13 Angra, Brazil Diablo Canyon, USA Braidwood, USA Double Chooz, France Krasnoyarsk, Russia KASKA, Japan Daya Bay, China RENO, Korea 8 proposals 4 cancelled 4 in progress

13 Angra Goal: sin 2 2  13 ~ 90% CL. Site: Rio de Janeiro, Brazil  30 researchers from 11 institutions.  Budget for Very Near (prototype) detector for Safeguards study approved by FINEP in March 2007 (~$0.5M)  High precision theta13 experiment in Angra around 2013?  Participation of the Brazilian group in Double Chooz experiment 4GW+1.8GW

14 Daya Bay Goal: LA: 40 ton Baseline: 500m Overburden: 112m Muon rate: 0.73Hz/m 2 Far: 80 ton 1600m to LA, 1900m to DYB Overburden: 350m Muon rate: 0.04Hz/m 2 DYB: 40 ton Baseline: 360m Overburden: 98m Muon rate: 1.2Hz/m 2 Access portal 8% slope 0% slope Goal: sin 2 2  13 < 90% CL in 3 years. Site: Shen Zhen, China Power Plant 4 cores 11.6 GW 6 cores 17.4 GW from 2011 Three experimental halls Multiple detectors at each site Side-by-side calibration Horizontal Tunnel Total length 3200 m Movable Detector All detectors filled at the filling hall, w/ the same batch of Gd-LS, w/ a reference tank Event Rate: ~1200/day Near ~350/day Far Backgrounds B/S ~0.4% Near B/S ~0.2% Far

15 Daya Bay Detector RPC Water Cherenkov Antineutrino detector  Eight 3-layer cylindrical anti-neutrino detectors, 5mx5m  Target mass 20 ton. Stable 0.1% Gd-LS by IHEP&BNL: [Gd+ carboxylic]+ LAB+fluor  Gamma catcher ~ 42cm, LAB+fluor  Oil Buffer ~ 50 cm, in PMTs + reflective panels. Energy resolution ~12%/sqrt(E)  Water shield (2 layer water cherenkov) ~ 250 cm, ~2000 ton. 4 layer RPC at top. 20 t Gd-LS Gamma Catcher Oil Buffer Reflective panel

16 Civil Construction Underground Filling in hall 5  Significantly reduce detector systematic uncertainties.  Same batch of Gd-LS and LS  H/Gd ratio, H/C ratio, light properties  A reference tank with load cell to fill all detectors  Target mass % Site Survey, bore hole Conceptual Design Preliminary Design Engineering Design Civil Bidding Start civil construction Complete civil construction Hall 5: LS mixing and filling 200t Gd-LS 200t LS 200t Oil

17 Daya Bay Status  ~180 collaborators, 34 institutes from China (Taiwan, Hong Kong), Czech, Russia, and United States.  All funding from China (all civil and ~50% detector) is secured.  Passed US DOE physics review ( ) and CD1 review (2007.4). R&D funding approved. CD2/3a review scheduled in Detector construction funding (~50% detector) expected shortly after CD2/3a.  Funding from Taiwan, Czech, Russia is secured. Schedule Start Tunnel Construction ……………… Surface Assembly Building ready ……… DB Near Hall civil complete …………… DB Near Site ready to take data ……… LA Near Site ready to take data ……… All Sites Ready to take Data…………… % C.L.

18 Daya Bay R&D  A 2-layer prototype running at IHEP for 1.5 years. Outer detector: 2mx2m, Inner acrylic vessel: 1mx1m.  Phase-I with 800 liters normal LS for 1 year.  Phase-II with 800 liters 0.1% Gd-LS has been running for 7 months.  A 2-layer prototypes is under construction in Hong Kong. (underground)  3-m and 4-m Acrylic Vessel prototype will be completed before  All critical detector components are being prototyped, e.g. water system, reflectors, RPC chamber, electronics, PMT base and seal, etc. Prototype with 45 8” PMTs Stability monitoring of 800-L 0.1% Gd-LS in IHEP prototype. No visible attenuation length degradation.

19 Double Chooz Goal: sin 2 2  13 < 90% CL in 3 years Ardennes, France Far detector (1050 m) 300 m.w.e. Near detector (~280 m) ~80 m.w.e. ν ν ν ν ν ν ν  2 reactors GW th  2 identical detectors: ► Target: 2 x 8.3 t  Comparison of neutrino rate & energy spectrum  Civil work: ► 1 near lab is foreseen ► 1 far lab is available Far site already exists

20 Double Chooz Detector  3-layer cylindrical detector  Target mass 8.3 ton. Stable Gd-LS by Heidelberg: [Gd+Beta-Dikotonates]+[20% PXE+80% dodecane]+fluor  Gamma catcher ~ 54cm, normal LS  Oil Buffer ~ 100 cm, in PMTs  Veto ~ 50 cm, shielding 15cm

21 Double Chooz Status  Proposal of the experiment (hep-ex/ )  Technical Design Report almost finished  Funding has been established in Europe  NSF groups in US funded  Japan and US DOE groups pending  The experiment is moving forward  Schedule:  : Detector construction and integration  2008: Far detector data taking starts, sin 2 2  13 < 0.06 (90% CL)  2010: Near detector starts ~100 scientists, 32 institutions from Brazil, France, Germany, Japan, Russia, Spain, UK, and US. The experiment has been approved by most of the respective Scientific Councils 90% C.L.  m 2 atm = eV 2

22 RENO YongGwang NPP, Korea 6 cores, 16.4 GW Goal: sin 2 2  13 ~ 90% CL in 3 years

23 RENO Detector  Target 15-t 0.1% Gd-LS, [Gd+CBX or BDK] + [20%PC+80% dodecane] + fluor, R&D by INR/IPCE group  Gamma Catcher ~60 cm  Oil Buffer ~70 cm, in PMTs, 7.7%/sqrt(E)  Water veto ~1 m, PMT number undetermined.

24 RENO Status  Experiment site usage has been approved.  Geological survey completed in  Issue tunnel construction contract in  Detector Construction begin in  Data taking expected to start in early collaborators, 13 institutes from Korea, Russia Project was approved for funding in 2005 with 10M USD.

25 RENO R&D  Small prototype running  Working on “mock-up” detector  Gd-LS R&D 4-L Gd-LS 140-L gamma catcher

26  TEXONO Collaboration – Academia Sinica-based and run, with groups from China, Turkey & India, close partnership with KIMS group in Korea.  Facilities – Kuo-Sheng Reactor Neutrino Laboratory in Taiwan; YangYang Underground Laboratory in South Korea.  Program – Low Energy Neutrino and Astroparticle (Dark Matter) Physics. Neutrino Magnetic Moments, Neutrino Radiative Decays, Axions Y2L TEXONO

27 Reactor Neutrino Interaction Cross-Sections R&D (ULEGe) :  Coh. ( N)  T < 1 keV Results (HPGe):   ( e )  T ~ keV On-Going Data Taking & Analysis [CsI(Tl)] :  SM  ( e)  T > 2 MeV massqualityDetector requirements Bkg level at O(10 keV)~ 1 counts / kg-keV-day

28 TEXONO 2007 Highlights Improved Limits in Neutrino Magnetic Moments (PRL-03, PRD-07)   e  < 7.4 X  90% CL Bounds on neutrino radiative decays. Reactor Axion (PRD-07):  Improved laboratory limits axion mass eV  Exclude DFSZ/KSVZ Models for axion mass eV  On-Going – measurements of neutrino-electron scattering cross-sections (i.e. sin 2  w at MeV)  Future – develop 100 eV threshold + 1 kg mass detector for  First observation of neutrino-nucleus coherent scattering  Dark matter searches for WIMP-mass less then 10 GeV  Improvement of neutrino magnetic moment sensitivities

29 Summary  Precisely measuring  13 is one of the highest priority in neutrino oscillation study. Sensitivity to sin 2 2  13 < 0.01 is achievable based on experiences of past reactor neutrino experiments.  Four theta13 experiments are in progress. Three of them project similar timeline, full operation starting in Double Chooz will get 0.06 before 2010 using a single far detector. Luminosity in 3 year (ton·GW·y) Overburden near/far (mwe) Projected Sensitivity Projected Full operation date Daya Bay /950<0.01End of 2010 Double Chooz21080/ ~ RENO74090/440~0.02Early 2010  Limit on neutrino magnetic moment is improved to be < 7.4 X  B by TEXONO. Many interesting physics topics can be carried out at very near neutrino scattering experiment.

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