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

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.

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

q13 Reactor Neutrino Detectors MO LS H2O Gd-LS

RENO Collaboration Reactor Experiment for Neutrino Oscillation (11 institutions and 40 physicists) Chonbuk National University Chonnam National University Chung-Ang University Dongshin University GIST Gyeongsang National University Kyungpook National University Sejong University 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 YongGwang (靈光) :

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

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

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

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

Gd Loaded Liquid Scintillator Recipe of Liquid Scintillator Solvent & Flour WLS Gd-compound LAB PPO + Bis-MSB 0.1% Gd + (TMHA)3 Steady properties of Gd-LS Stable light yield (~250 pe/MeV) , transparency & Gd concentration (0.11%) NIM A, 707, 45-53 (2013. 4. 11)

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

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

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

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

Neutron Capture by Gd

Backgrounds m n m n m 9Li g p e n 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 muon spallation Accidentals Fast neutrons 9Li/8He b-n followers m n Gd m n m 9Li g p e Gd n Gd

Measured Spectra of IBD Prompt Signal Bkg.: 2.2 % Bkg.: 7.2 % 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 %)

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

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

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)

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.

IBD Sample with n-H Neutron-H Capture cut criteria preliminary Prompt Energy 0.7 ~ 12 MeV Delayed Energy 1.95~2.50 MeV deltaT 2 ~ 400 us deltaR < 50 cm Qmax/Qtot < 0.08 Muon Veto time 1 ms Shower Muon Veto time 700 ms Additional Trigger veto time cuts n-H IBD Event Vertex Distribution target g-catcher

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

Reactor Neutrino Oscillations Short Baseline Long Baseline [Nunokawa & Parke (2005)] cos 2 𝜃 12 Δ 𝑚2 21

Energy Calibration from g-ray Sources

Energy Calibration from B12 b-decays Near detector

Far detector

B12 Energy Spectrum (Near & Far)

Interacting Reactor Isotope Fraction Averaged from the six reactors

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)

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 !!

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%) Far Detector 17102 (BG: 5.5%) 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??

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

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

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

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] DB: 139 days [1210.6327] DC: n-H [1301.2948] RENO: 403 days [NuTel2013] DC: RRM analysis [1305.2734] DB: 190 days [1310.6732] 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]

13 from 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

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

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, Dm221 and 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

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

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

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

Additional Physics with RENO-50 Neutrino burst from a Supernova in our Galaxy - ~5,600 events (@8 kpc) (* NC tag from 15 MeV deexcitation g) - 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

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

Thanks for your attention!