Recent Results from RENO & Future Plan

1. Recent Results from RENO & Future Plan Soo-Bong Kim (KNRC, Seoul National University) “Fermilab, July 25, 2014”

2. Remembrance • Yoji Totsuka, who discovered the neutrino oscillation, was a big supporter for the RENO experiment. • I would like to remember him with our RENO results on q13. Yoji Totsuka (1942~2008) • Credit to L. Mikaelyan & V. Sinev for two identical detectors • Maury Goodman’s neutrino newsletter (5/5/2012): • F. Darwin said “In Science the credit goes to the man who convinces the world, not to the man to whom the idea first occurred.” • But he wishes to give credit to Russians who first proposed a two detector neutrino reactor disappearance experiment : L. Mikaelyan & V. Sinev.

3. Reactor 13 Experiments RENO at Yonggwang, Korea Double Chooz at Chooz, France Daya Bay at Daya Bay, China

4. q13 Reactor Neutrino Detectors MO LS H2O Gd-LS

5. YongGwang (靈光) : RENO Collaboration Reactor Experiment for Neutrino Oscillation (11 institutions and 40 physicists) • Chonbuk National University • Chonnam National University • Chung-Ang University • DongshinUniversity • GIST • Gyeongsang National University • Kyungpook National University • SejongUniversity • Seoul National University • Seoyeong University • Sungkyunkwan University • Total cost : $10M • Start of project : 2006 • The first experiment running with both near & far detectors from Aug. 2011

6. RENO Experimental Set-up 120 m.w.e. Near Detector 290m 1380m Far Detector 450 m.w.e.

7. RENO Detector • 354 ID +67 OD 10” PMTs • Target : 16.5 ton Gd-LS, R=1.4m, H=3.2m • Gamma Catcher : 30 ton LS, R=2.0m, H=4.4m • Buffer : 65 ton mineral oil, R=2.7m, H=5.8m • Veto : 350 ton water, R=4.2m, H=8.8m

8. RENO Status • Data taking began on Aug. 1, 2011 with both near and far detectors. • (DAQ efficiency : ~95%) Near Detector • A (220 days) : First q13 result • [11 Aug, 2011~26 Mar, 2012] • PRL 108, 191802 (2012) A • B (403 days) : Improved q13 result • [11 Aug, 2011~13 Oct, 2012] • NuTel 2013, TAUP 2013, WIN 2013 Now Far Detector • C (~800 days) : Newq13 result Shape+rate analysis (in progress) • [11 Aug, 2011~31 Dec, 2013] B C (new results) • Total observed reactor neutrino events as of today : ~ 1M (Near), ~ 0.1M(Far) • → Absolute reactor neutrino flux • measurement in progress • [reactor anomaly & sterile neutrinos]

9. Detection of Reactor Antineutrinos (prompt signal) (delayed signal) ~200 ms + p  D + g (2.2 MeV) ~26 ms (0.1% Gd) + Gd  Gd + g‘s (8 MeV) • Neutrino energy measurement

10. Gd Loaded Liquid Scintillator • Recipe of Liquid Scintillator • Steady properties of Gd-LS • Stable light yield (~250 pe/MeV) , transparency & Gd concentration (0.11%) NIM A, 707, 45-53 (2013. 4. 11)

11. Liquid(Gd-LS/LS/MO/Water) Production & Filling (May-July 2011) Gd-LS filling for Target Gd Loaded Liquid Scintillator Water filling for Veto LS filling for Gamma Catcher Gd Loaded Liquid Scintillator

12. Yonggwang Neutrino Detector Facility • 3~6인 상주 : 검출시설 관리 및 작동 (발전소 사택 아파트 2채 임대 사용 중)

13. New RENO Results at Neutrino 2014 • ■~800 days of data • ■New measured value of q13 from rate-only analysis • ■Observation of a new reactor neutrino component at 5 MeV • ■Results of reactor neutrinos with neutron capture on H

14. IBD Event Signature • Prompt signal (e+) : 1 MeV 2g’s + e+ kinetic energy (E = 1~10 MeV) • Delayed signal (n) : 8 MeVg’s from neutron’s capture by Gd • ~26 ms (0.1% Gd) in LS → Prompt Signal Delayed Signal

15. Neutron Capture by Gd

16. Backgrounds • Accidental coincidence between prompt and delayed signals • Fast neutrons produced by muons, from surrounding rocks and inside detector (n scattering : prompt, n capture : delayed) • 9Li/8He b-n followers produced by cosmic muonspallation Accidentals m Fast neutrons 9Li/8He b-n followers m m p g 9Li n n e Gd Gd Gd n

17. Measured Spectra of IBD Prompt Signal Bkg.: 7.2 % Bkg.: 2.2 % Near Live time = 761.11 days # of IBD candidate = 433,196 # of background = 9499 (2.2 %) Far Live time = 794.72 days # of IBD candidate = 50,750 # of background = 3672 (7.2 %)

18. Observed Daily Averaged IBD Rate preliminary • Good agreement with observed rate and prediction. • Accurate measurement of thermal power by reactor neutrinos

19. Observed vs. Expected IBD Rates sin22q13= 0.101 |Δm312| = 2.32 x 10-3 eV2 - Good agreement between observed rate & prediction - Indication of correct background subtraction

20. New q13 Measurement by Rate-only Analysis (Preliminary) 4.9 s (Neutrino 2012)  6.3 s (TAUP/WIN 2013)  0.101 +/- 0.013 7.8 s (Neutrino 2014)

21. Why n-H IBD Analysis? Motivation: 1. Independent measurement of q13 value. 2. Consistency and systematic check on reactor neutrinos. * RENO’s low accidental background makes it possible to perform n-H analysis. -- low radio-activity PMT -- successful purification of LS and detector materials.

22. IBD Sample with n-H preliminary n-H IBD Event Vertex Distribution g-catcher target

23. Results from n-H IBD sample Very preliminary Rate-only result (B data set) preliminary preliminary Near Detector Far Detector

24. Reactor Neutrino Oscillations Long Baseline Short Baseline [Nunokawa & Parke (2005)]

25. Energy Calibration from g-ray Sources

26. Energy Calibration from B12 b-decays Near detector

27. Far detector

28. B12 Energy Spectrum (Near & Far)

29. Interacting Reactor Isotope Fraction Averaged from the six reactors

30. Observation of a New Reactor Neutrino Component at 5 MeV • Fraction of 5 MeV excess (%) to expected flux[2011 Huber+Mueller] • Near : 2.314 +/- 0.401 (experimental) +/- 0.492 (expected shape error) • Far : 1.862 +/- 0.708 (experimental) +/- 0.486 (expected shape error)

31. Correlation of 5 MeV Excess with Reactor Power 5 MeV excess has a clear correlation with reactor thermal power ! All the six reactors are on two or three reactors are off A new reactor neutrino component !!

32. Observed Spectra of IBD Prompt Signal • The expected IBD prompt spectra from the RENO MC do not reproduce the shape in the energy region of 4~6 MeV..... Near Detector 154088 (BG: 2.7%) RENO slide from Neutrino 2012, Kyoto • Need more detailed energy calibration between 3 and 8 MeV using new radioactive sources. • Any new components of background sources? • Is the prediction of reactor neutrino spectra correct?? Far Detector 17102 (BG: 5.5%)

33. The 5 MeV Excess Seen at Double-Chooz and Daya Bay Daya Bay, ICHEP 2014 Double-Chooz, Neutrino 2014

34. Shape Analysis for Dmee2 In progress…. Stay tuned… Without 5 MeV excess With 5 MeV excess

35. RENO’s Projected Sensitivity of q13 Neutrino 2014 (7.8 s) (~800 days) (14 s) (in 3 years) (13 % precision) (7 % precision) 2012. 4 • 5 years of data : ±7% • - stat. error : ±0.008 → ±0.005 • - syst. error : ±0.010 → ±0.005 • - shape information → ±5% 2013. 3 2013. 9 2014. 6 (7 % precision)

36. A Brief History of q13 from Reactor Experiments DC: 97 days [1112.6353] R+S DB: 49 days [1203.1669] RENO: 222 days [1204.0626] DC: 228 days [1207.6632] R+S DB: 139 days [1210.6327] DC: n-H [1301.2948] R+S RENO: 403 days [NuTel2013] DC: RRM analysis [1305.2734] R+S DB: 190 days [1310.6732] R+S RENO: 403 days [TAUP2013] DB: 190 days n-H [Moriond2014] DC: 469 days [n 2014] DB: 563 days [n 2014] RENO: 795 days [n 2014] 384 days n-H [n 2014]

37. 13from Reactor and Accelerator Experiments First hint of δCP combining Reactor and Accelerator data Best overlap is for Normal hierarchy & δCP = - π/2 Is Nature very kind to us? Are we very lucky? Is CP violated maximally? Strong motivation for anti-neutrino runs and precise measurements of θ13 Courtesy C. Walter (T2K Collaboration) Talk at Neutrino 2014

38. Summary • We observed a new reactor component at 5 MeV. (3.6 s) • New measurement of q13by rate-only analysis (preliminary) • Shape analysis for Dm2 in progress… (stay tuned) • First result on n-H IBD analysis (very preliminary) • sin2(2q13) to 7% accuracy within 3 years • → will provide the first glimpse of CP. • If accelerator results are combined.

39. Overview of RENO-50 • RENO-50 : An underground detector consisting of 18 kton ultra- low-radioactivity liquid scintillator & 15,000 20” PMTs, at 50 km away from the Hanbit(Yonggwang) nuclear power plant • Goals: - Determination of neutrino mass hierarchy - High-precision measurement of q12, Dm221and Dm231 - Study neutrinos from reactors, the Sun, the Earth, Supernova, and any possible stellar objects • Budget : $ 100M for 6 year construction (Civil engineering: $ 15M, Detector: $ 85M) • Schedule : 2014 ~ 2019 : Facility and detector construction 2020 ~ : Operation and experiment

40. Reactor Neutrino Oscillations at 50 km Neutrino mass hierarchy (sign of Dm231)+precise values of 12,Dm221 & Dm231 PreciseDm221 Large Deficit Precise q12 Ripple Mass Hierarchy

41. Near Detector Far Detector (NEAR Detector) (FAR Detector) RENO-50 10 kton LS Detector ~47 km from YG reactors Mt. Guemseong (450 m) ~900 m.w.e. overburden

43. 2012 Particle Data Book • Precise measurement of q12, Dm221 and Dm232 (±2.8%) sin2q12 = 0.312±0.017 (±5.4%) (← 5.4%) (← 2.7%) (← 5.2%) (±2.7%) ∆m212 / |∆m31(32)2| ≈ 0.03 (±3.1%) (+5.2-3.4%) (±13.3%)

44. Additional Physics with RENO-50 • Neutrino burst from a Supernova in our Galaxy • - ~5,600 events (@8 kpc) (* NC tag from 15 MeVdeexcitationg) • - A long-term neutrino telescope • Geo-neutrinos : ~ 1,000 geo-neutrinos for 5 years • - Study the heat generation mechanism inside the Earth • Solar neutrinos : with ultra low radioacitivity • - MSW effect on neutrino oscillation • - Probe the center of the Sun and test the solar models • Detection of J-PARC beam : ~200 events/year • Neutrinoless double beta decay search : possible modification like KamLAND-Zen

45. J-PARC neutrino beam Dr. Okamura & Prof. Hagiwara RENO-50

46. Thanks for your attention!