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K.K. Joo Chonnam National University

“New results from RENO & prospects with RENO-50”. K.K. Joo Chonnam National University. (On behalf of RENO Collaboration). July 05, 2016. The XXVII International Conference on Neutrino Physics and Astrophysics @ Imperial College London, London, United Kingdom. Outline. Data taking status

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K.K. Joo Chonnam National University

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  1. “New results from RENO & prospects with RENO-50” K.K. Joo Chonnam National University (On behalf of RENO Collaboration) July 05, 2016 The XXVII International Conference on Neutrino Physics and Astrophysics @ Imperial College London, London, United Kingdom

  2. Outline • Data taking status • Improvements in data analysis RENO • Overview/physics of RENO-50 RENO-50 • Summary

  3. Neutrino Mixing Angles ~45o(1998) Super-K; K2K q23 2015 Nobel Prize 34o(2001) SNO, Super-K; KamLAND q12 Atmospheric Neutrino Oscillation Reactor Neutrino Oscillation 9o(2012) Daya Bay, RENO Double Chooz q13 Solar Neutrino Oscillation “Neutrino has mass” “Established three-flavor mixing framework”

  4. YongGwang (靈光) : RENO Collaboration 9 institutions and 35 physicists in Korea • Chonnam National 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 sinceAug. 2011 New name: Hanbit Reactor Experiment for Neutrino Oscillation

  5. 200m high Near Detector Reactors 70m high 100m 300m 290m 1,380m Far Detector Google Satellite View of Experimental Site 16.5 GWth 120 m.w.e. • 6 reactors are lined up in roughly equal distances and span ~1.3 km • Total average thermal output ~16.5GWth 290m YongGwang Nuclear Power Plant 1380m

  6. RENO Detector • 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 (MO) • (R=2.7m, H=5.8m) • Veto : 350 ton water (R=4.2m, H=8.8m) • Inner PMTs: 354 10” PMTs • solid angle coverage = ~14% • Outer PMTs: ~ 67 10” PMTs total ~460 tons

  7. IBD signal: coincidence Inverse beta decay (ve + pe+ + n) Delayed signal (S2) Prompt signal (S1) n-Gd IBD ~30 ms 8 MeV n-H IBD S2 S1 ~200 ms 2.2 MeV

  8. RENO Data-taking Status • Data taking began on Aug. 1, 2011 with both near and far detectors. (DAQ efficiency : ~95%) A • A (220 days) : First q13 result [11 Aug, 2011~26 Mar, 2012] PRL 108, 191802 (2012) B Now • B (403 days) : Improved q13 result [11 Aug, 2011~13 Oct, 2012] NuTel 2013, TAUP 2013, WIN 2013 2011 2012 2013 2014 2015 2016 • C (~500 days) : Newresult • Shape+rate analysis (q13 and |Dmee2 |) • [11 Aug, 2011~21 Jan, 2013] • PRL 116, 211801 (2016) C D • D (~1400 days) : Absolute reactor flux and spectrum • [11 Aug. 2011~ 30 Sep, 2015] Total ~ 1700 days 2011 2012 2013 2014 2015 2016

  9. New Results from RENO • New measured value of q13 from rate-only analysis using ~500 days of data (Aug. 2011 ~ Jan. 2013) • Observation of an excess at ~5 MeV in reactor neutrino spectrum • Observation of energy dependent disappearance of reactor neutrinos to measure Dmee2 and q13 “Observation of Energy and Baseline Dependent Reactor Antineutrino Disappearance in the RENO Experiment” (published in PRL 116, 211801, 2016) - Details can be found there & PRD to be submitted soon • Independent measurement of q13 with n-H for a delayed signal (additional background reduction in progress) • Obtained result from sterile neutrinos search

  10. Observed Delayed Signal (n-Gd) IBD (ve + p e+ + n) Delayed energy distribution (S2)

  11. Measured Spectra of IBD Prompt Signal Near Live time = 458.49 days # of IBD candidate = 290,775 # of background = 8,041 (2.8 %) Far Live time = 489.93 days # of IBD candidate = 31,541 # of background = 1540 (4.9 %)

  12. IBD Candidates & Backgrounds

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

  14. The 5 MeV Excess is there ! RENO Double Chooz Daya Bay Neutrino 2014, Boston In 2014, RENO showed that the 5 MeV excess is from reactor neutrinos. Hawaii 2014

  15. Observation of an excess at 5 MeV (Preliminary) 1400 days of data (Aug. 2011 – Sep 2015) The measured near spectrum is compared with prediction using χ2-square test. Fraction of 5 MeV excess: 2.46 ± 0.27 (%) ~3% Significance of the 5 MeV excess: ~9σ ~2.5%

  16. Correlation of 5 MeV Excess with Reactor Power 5 MeV excess has a clear correlation with reactor thermal power ! 1400 days of data two or three reactors are off All the six reactors are on The 5 MeV excess comes from reactors!

  17. Correlation of 5 MeV excess with 235U isotope fraction (Preliminary) 235U fraction corresponds to freshness of reactor fuel Δχ2 = 1.174 P-value = 0.240 (Beginning of reactor cycle) (End of reactor cycle)

  18. Measurement of Absolute Reactor Neutrino Flux • R (data/prediction) = 0.946 +- 0.021 (500 days) • The flux prediction is with Huber + Mueller model • Flux weighted baseline at near : 411 m Comparison with other experiments Preliminary Daya Bay *Prediction is corrected for three flavor neutrino oscillation Poster: “Precise measurement of reactor neutrino flux and spectrum at RENO” (E. H. Kwon)

  19. νe νe νe νe νe νe sin22θ13 Reactor Neutrino Oscillations Oscillations observed as a deficit of anti-neutrinos the position of the minimum is defined by Δm2ee 1.0 Probability νe flux before oscillation observed here Distance 1200 to 1800 meters H. Nunokawa et al, PRD72 013009(2005)

  20. Energy Calibration from g-ray Sources • Non-linear resonse of the scintillation energy is calibrated using γ-ray source Fit function : Evis/Etrue = a – b/(1 – exp(-cEtrue – d)) • Deviation of all calibration data points with respect to the best-fit is within ~1% Poster: “Prompt energy calibration at RENO” (S. Y. Kim)

  21. 12B Energy Spectrum (Near & Far) • Electron energy spectrum from β-decays from 12B and 12N, which are produced by cosmic-muon interactions Good agreement between data and MC spectrum!

  22. Energy Scale Difference between Near & Far Energy scale difference < 0.15% forEp = 1~8 MeV

  23. Energy Dependent Disappearance L/E Dependent Disappearance PRL 116, 211801, 2016 Clear energy-dependent disappearance of reactor antineutrinos Poster: “Spectral measurement of q13 and |Dmee2|at RENO (H. K. Seo)

  24. Summary of New Oscillation Results Rate Only ± 0.011(total) Rate + Shape ± 0.26 (total) 10 % precision ± 0.010(total) 12 % precision • arXiv:1511.05849.v2 • PRL 116, 211801 (2016) • PRD to be submitted soon

  25. Projected Sensitivity of q13 & |Dmee2| (±12%) (±6 %) (±6 %) (±10%) (~500 days) (5 years of data) (6 % precision) (sensitivity goal of q13 ) Seminar @ CERN

  26. n-H IBD Analysis Motivation: 1. Independent measurement of q13 value. 2. Consistency and systematic check on reactor neutrinos. n-H IBD Event Vertex Distribution target g-catcher Poster: “Measurement of q13using RENO reactor neutrino events with neutron capture on hydrogen” (C. D. Shin)

  27. Delayed spectrum and capture time • Delayed signal peak: • ~2.2 MeV • Mean coincidence time: • ~ 200 ms Capture time (n-H) Far and near data match very well 27

  28. q13 Measurement with n-H Data set : 2011/08 ~ 2013/01 (~500 days) Preliminary rate only analysis results is

  29. Light Sterile Neutrino Search Results (Preliminary) • All 500 days of RENO data • Consistent with standard 3-flavor neutrino oscillation model • Able to set stringent limits in the region eV2 full curves assumes Paper now in preparation Poster: “Search for sterile neutrinos at RENO ” (I. S. Yeo)

  30. Summary (1st part) • New measurement of q13 by rate-only analysis • Observed an excess at 5 MeV in reactor neutrino spectrum • Observation of energy dependent disappearance of reactor neutrinos and our first measurement ofDmee2 ± 0.26(total) 10 % precision ± 0.010(total) 12 % precision • RENO (goal): sin(2q13) to 6% accuracy • Dmee2 to 0.15×10-3 eV2 (6%) for final sensitivity

  31. 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 Dm2ee - Supernova neutrinos, Geo neutrinos, Sterile neutrino search, …. • Budget : $ 100M for 6 year construction (Civil engineering: $ 15M, Detector: $ 85M) • Schedule : 2016 ~ 2021 : Facility and detector construction 2022 ~ : Operation and experiment

  32. Various Physics with RENO-50 • Determination of neutrino mass ordering • - 3s sensitivity with 10 years of data • Precise (~0.5%) measurement of q12, Dm221 and Dm2ee • - An interesting test for unitarity & essential for the future discoveries • Neutrino burst from a Supernova in our Galaxy • - Study the core collapsing mechanism with neutrino cooling • Geo-neutrinos : ~ 1,500 geo-neutrinos for 5 years • - Study the heat generation mechanism inside the Earth • Solar neutrinos • - MSW effect on neutrino oscillation • Sterile neutrino search : reactor / radioactive sources / IsoDAR • Detection of J-PARC beam : ~200 events/year

  33. Courtesy by YoshitaroTakaesu (Tokyo) Near Detector Far Detector (NEAR Detector) (FAR Detector) RENO-50 18 kton LS Detector ~47 km from YG reactors Mt. Guemseong (450 m) ~900 m.w.e. overburden

  34. RENO-50 Candidate Site Mt. GuemSeong Altitude : 450 m Dongshin University RENO-50 Candidate Site City of Naju

  35. Conceptual Design of RENO-50 Detector Geological Survey for Underground Facility Cost estimation for RENO-50 underground facility (in progress)  Geological survey for design of tunnel and experimental hall  Cost estimation to be obtained soon 39 m Water, 1000 20” PMTs LS (18 kton) 15000 20” PMTs 39 m RENO-50 detector (MC)

  36. RENO-50 R&D Status in Progress (1) Development of DAQ electronics is on-going (2) Develop techniques of LS purification is on-going (3) Mechanical design of detector is on-going (4) Measurement of radioactivity for the detector materials is on-going (5) Upgrade of measurement device for absolute LS attenuation length is on-going Current status • An R&D funding (US $2M for 3 years of 2015-2017) is given by the Samsung Science & Technology Foundation. • Efforts on obtaining a full construction fund Poster: “Status and R&D of RENO-50” (Sunny Seo)

  37. Summary of RENO/RENO-50 • New results are presented • Clear observation of 5 MeV excess • Absolute antineutrino flux measurement (R = 0.946 +- 0.021 ) • Independent measurement of q13 with n-H • Excluded region for sterile neutrinos • RENO-50: various R&D in progress *(For more details, please see RENO 6 posters)

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