Reactor Neutrino Experiments Jun Cao caojihep ac cn

Reactor Neutrino Experiments Jun Cao caoj@ihep. ac. cn Institute of High Energy Physics Lepton-Photon 2007, Daegu, Aug. 13 -18, 2007

Outline 2 u Past Reactor Neutrino Experiments ð Palo Verde ð Chooz ð Kam. LAND u Theta 13 experiments ð ð u Angra Daya Bay Double Chooz RENO Search for neutrino magnetic moment ð TEXONO u Summary

3 Past Reactor Neutrino Experiments Reactor anti-neutrino experiments have played a critical role in the 50 year-long history of neutrinos. u The first neutrino observation in 1956 by Reines and Cowan. u Determination of the upper limit of mixing angle theta 13 to sin 22 13<0. 17 (Chooz, Palo Verde) u The first observation of reactor anti-neutrino disappearance at Kam. LAND in 2003. Now reactor neutrino experiments become prominent again for measuring mixing angle 13 precisely.

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

Reactor Neutrino Spectra 5 u u u 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 theta 13 experiments. Peak at 4 Me. V

CHOOZ 6 Baseline 1. 05 km 1997 -1998, France 8. 5 GWth 300 mwe 5 ton 0. 1% Gd-LS Bad Gd-LS R=1. 01 2. 8%(stat) 2. 7%(syst), sin 22 13<0. 17 Parameter Relative error Reaction cross section 1. 9 % Number of protons 0. 8 % Detection efficiency 1. 5 % Reactor power 0. 7 % Energy released per fission 0. 6 % Combined 2. 7 % Eur. Phys. J. C 27, 331 (2003)

Palo Verde 7 1998 -1999, US 11. 6 GWth Segmented detector 12 ton 0. 1% Gd-LS Shallow overburden 32 mwe Baseline 890 m & 750 m R=1. 01 2. 4%(stat) 5. 3%(syst) 60%/year Chooz Gd-LS Palo Verde Gd-LS 1 st year 12%, 2 nd year 3% Phys. Rev. D 64, 112001(2001)

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

9 Kam. LAND R=0. 658 0. 044(stat) 0. 047(syst) The first observation of reactor anti-neutrino disappearance Confirmed antineutrino disappearance at 99. 998% CL Excluded neutrino decay at 99. 7% CL Excluded decoherence at 94% CL Phys. Rev. Lett. 94, 081801 (2005)

10 Neutrino Oscillation Neutrino Mixing: PMNS Matrix Atmospheric, K 2 K, MINOS, T 2 K, etc. 23 ~ 45º Reactor Accelerator 13 < 12º Solar Kam. LAND 12 ~ 30º Known: |Dm 232|, sin 22 23, Dm 221, sin 22 12 Unkown: sin 22 13, d. CP, Sign of Dm 232 “We recommend, as a high priority, …, An expeditiously deployed multi-detector reactor experiment with sensitivity to e disappearance down to sin 22 13=0. 01” ---- APS Neutrino Study, 2004

Precisely Measuring theta 13 11 Major sources of uncertainties: u Reactor related ~2% u Detector related ~2% u Background subtraction Lessons from past experience: u Need near and far detectors u Chooz: Good Gd-LS u Palo Verde: Go deeper u Kam. LAND: No fiducial cut, lower threshold Parameter 4 Me. V Relative error By Near/far configuration Reaction cross section 1. 9 % Cancel out Number of protons 0. 8 % Reduced to ~0. 3% Detection efficiency 1. 5 % Reduced to 0. 2~0. 6% Reactor power 0. 7 % Cancel out or reduced to ~0. 1% Energy released per fission 0. 6 % Cancel out Chooz Combined 2. 7 %

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

13 Angra Goal: sin 22 13 ~ 0. 006 @ 90% CL. Site: Rio de Janeiro, Brazil u 30 researchers from 11 institutions. u Budget for Very Near (prototype) detector for Safeguards study approved by FINEP in March 2007 (~$0. 5 M) u High precision theta 13 experiment in Angra around 2013? u Participation of the Brazilian group in Double Chooz experiment 4 GW+1. 8 GW

Daya Bay 14 Goal: sin 22 13 < 0. 01 @ 90% CL in 3 years. Site: Shen Zhen, China Goal: Far: 80 ton 1600 m to LA, 1900 m to DYB 0% slope Overburden: 350 m 2 Muon rate: 0. 04 Hz/m LA: 40 ton Baseline: 500 m Overburden: 112 m Muon rate: 0. 73 Hz/m 2 0% slope Access portal 8% slope DYB: 40 ton Baseline: 360 m Overburden: 98 m Muon rate: 1. 2 Hz/m 2 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 u u u Daya Bay Detector Eight 3 -layer cylindrical anti-neutrino detectors, 5 mx 5 m Target mass 20 ton. Stable 0. 1% Gd-LS by IHEP&BNL: [Gd+carboxylic]+LAB+fluor Gamma catcher ~ 42 cm, LAB+fluor Oil Buffer ~ 50 cm, 192 8 -in PMTs + reflective panels. Energy resolution ~12%/sqrt(E) Water shield (2 layer water cherenkov) ~ 250 cm, ~2000 ton. 4 layer RPC at top. Oil Buffer Gamma Catcher RPC 20 t Gd-LS Antineutrino detector Water Cherenkov Reflective panel

Civil Construction 16 Site Survey, bore hole 2005. 5 -2006. 6 Conceptual Design 2006. 6 -2006. 8 Preliminary Design 2007. 1 -2007. 3 Engineering Design 2007. 3 -2007. 7 Civil Bidding 2007. 8 -2007. 9 Start civil construction 2007. 9 Complete civil construction 2009. 6 Underground Filling in hall 5 Significantly reduce detector systematic uncertainties. 200 t LS 200 t Oil 200 t Gd-LS Hall 5: LS mixing and filling ð ð 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 0. 1 -0. 2%

17 u u 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 (2006. 10) and CD 1 review (2007. 4). R&D funding approved. CD 2/3 a review scheduled in 2007. 11. Detector construction funding (~50% detector) expected shortly after CD 2/3 a. Funding from Taiwan, Czech, Russia is secured. Schedule Start Tunnel Construction ……………… 2007. 09 Surface Assembly Building ready ……… 2008. 06 DB Near Hall civil complete …………… 2008. 07 DB Near Site ready to take data ………. 2009. 06 LA Near Site ready to take data ……… 2010. 05 All Sites Ready to take Data…………… 2010. 10 90% C. L.

Daya Bay R&D 18 u A 2 -layer prototype running at IHEP for 1. 5 years. Outer detector: 2 mx 2 m, Inner acrylic vessel: 1 mx 1 m. ð ð u u u 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 2007. 11 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.

Double Chooz 19 Goal: sin 22 13 < 0. 03 @ 90% CL in 3 years Near detector (~280 m) ~80 m. w. e. Far detector (1050 m) 300 m. w. e. νν Ü 2 reactors - 8. 5 GWth Ü 2 identical detectors: ►Target: 2 x 8. 3 t Ü Comparison of neutrino rate & energy spectrum Ü Civil work: ► 1 near lab is foreseen ► 1 far lab is available ν ν ν Far site already exists Ardennes, France

20 u u u 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 ~ 54 cm, normal LS Oil Buffer ~ 100 cm, 390 10 -in PMTs Veto ~ 50 cm, shielding 15 cm

21 Double Chooz Status ~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 u u u Proposal of the experiment (hep-ex/0606025) Technical Design Report almost finished Funding has been established in Europe ð NSF groups in US funded ð Japan and US DOE groups pending The experiment is moving forward 90% C. L. m Schedule: ð 2007 -2008: Detector construction and integration ð 2008: Far detector data taking starts, sin 22 13 < 0. 06 (90% CL) ð 2010: Near detector starts 2 atm = 2. 8 10 -3 e. V 2

22 Yong. Gwang NPP, Korea 6 cores, 16. 4 GW RENO Goal: sin 22 13 ~ 0. 02 @ 90% CL in 3 years

23 RENO Detector u u 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, 537 8 -in PMTs, 7. 7%/sqrt(E) Water veto ~1 m, PMT number undetermined.

24 RENO Status 43 collaborators, 13 institutes from Korea, Russia Project was approved for funding in 2005 with 10 M USD. u u u Experiment site usage has been approved. Geological survey completed in 2007. 05 Issue tunnel construction contract in 2007. 10 Detector Construction begin in 2007. 10 Data taking expected to start in early 2010.

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

26 TEXONO Ø TEXONO Collaboration – Academia Sinica-based and run, with groups from China, Turkey & India, close partnership with KIMS group in Korea. Ø Facilities – Kuo-Sheng Reactor Neutrino Laboratory in Taiwan; Yang Underground Laboratory in South Korea. Ø Program – Low Energy Neutrino and Astroparticle (Dark Matter) Physics. Neutrino Magnetic Moments, Neutrino Radiative Decays, Axions Y 2 L

27 Reactor Neutrino Interaction Cross-Sections quality Detector requirements mass Bkg level at O(10 ke. V)~ 1 counts / kg -ke. V-day On-Going Data Taking & Analysis [Cs. I(Tl)] : R&D (ULEGe) : ØCoh. (n. N) ØT < 1 ke. V Results (HPGe): ØSM s(ne) Ømn(ne) ØT > 2 Me. V ØT ~ 1 -100 ke. V

28 TEXONO 2007 Highlights Improved Limits in Neutrino Magnetic Moments (PRL-03, PRD-07) mn(ne) < 7. 4 X 10 -11 m. B @ 90% CL Bounds on neutrino radiative decays. Reactor Axion (PRD-07): p Improved laboratory limits axion mass 102 -106 e. V p Exclude DFSZ/KSVZ Models for axion mass 104106 e. V u On-Going – measurements of neutrino-electron scattering cross-sections (i. e. sin 2 w at Me. V) u Future – develop 100 e. V threshold + 1 kg mass detector for ð First observation of neutrino-nucleus coherent scattering ð Dark matter searches for WIMP-mass less then 10 Ge. V

Summary 29 Precisely measuring 13 is one of the highest priority in neutrino oscillation study. Sensitivity to sin 22 13 < 0. 01 is achievable based on experiences of past reactor neutrino experiments. Four theta 13 experiments are in progress. Three of them project similar timeline, full operation starting in 2010. Double Chooz will get 0. 06 before 2010 using a single far detector. u u u Luminosity in 3 year (ton·GW·y) Overburden near/far (mwe) Projected Sensitivity Projected Full operation date Daya Bay 4200 270/950 <0. 01 End of 2010 Double Chooz 210 80/300 0. 02~0. 03 2010 RENO 740 90/440 ~0. 02 Early 2010 Limit on neutrino magnetic moment is improved to be < 7. 4 X 10 -11 B by TEXONO. Many interesting physics topics can be carried out at very near neutrino scattering experiment.

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