Soo-Bong Kim Seoul National Univ.

1. Current Status of RENO (Symposium on “Physics of Massive Neutrinos” May 20-22, 2008, Milos, Greece) Soo-Bong Kim Seoul National Univ.

2. New Reactor Neutrino q13Experiment • CHOOZ : Rosc = 1.01 ± 2.8% (stat) ± 2.7% (syst) • Larger statistics - More powerful reactors (multi-core) - Larger detection volume - Longer exposure → Obtain ~1% precision !!! • Smaller experimental errors - Identical multi detectors • Lower background - Improved detector design - Increased overburden

3. (3) 1μs<ΔT <200μs n captureenergy e+ energy (1) 0.7<Eprompot <9MeV (2) 5<Edelayed <11MeV data from CHOOZ hep-ex/0301017v1 Detection of Reactor Neutrinos

4. RENO Collaboration • Chonnam National University • Dongshin University • Gyeongsang National University • Kyungpook National University • Pusan National University • Sejong University • Seoul National University • Sungkyunkwan University • Institute of Nuclear Research RAS (Russia) • Institute of Physical Chemistry and Electrochemistry RAS (Russia) +++ http://neutrino.snu.ac.kr/RENO

6. Schematic Setup of RENO at YeongGwang

7. Google Satellite View of YeongGwang Site

8. 200m high Near Detector Reactors 70m high 100m 300m 290m 1,380m Far Detector Schematic View of Underground Facility

9. 2009 2006 2007 2008 Activities 12 12 12 12 3 3 3 3 6 6 6 6 9 9 9 9 Detector Design & Specification Geological Survey & Tunnel Design Detector Construction Excavation & Underground Facility Construction Detector Commissioning Schedule

10. Comparison of Reactor Neutrino Experiments

11. Summary of Construction Status • 03~10, 2007 : Geological survey and tunnel design are completed. • 05~12, 2008 : Tunnel construction • Hamamatsu 10” PMTs are considered to be purchased. • (expect to be delivered from March 2009) • SK new electronics are adopted and ordered. • (will be ready in Sep. 2008) • Steel/acrylic containers and mechanical structure will be ordered soon. • Liquid scintillator handling system is being designed. • Mock-up detector (~1/4 in length) will be made in June, 2008.

12. Rock sampling (DaeWoo Engineering Co.) Rock samples from boring

13. Far detector site: • tunnel length : 272m • overburden • height : 168.1m Rock quality map • Near detector site: • tunnel length : 110m • overburden • height : 46.1m

14. Stress analysis for tunnel design

16. Detector Design with MC Simulation • RENO-specific MC simulation based on GLG4sim/Geant4 • Detailed detector design and drawings are completed • Detector performance study &Detector optimization with MC: - Gamma catcher size - Buffer size - photo-sensor coverage (no. of PMTs) - neutron tagging efficiency as a function of Gd concentration • Reconstruction(vertex position & energy) program written • Systematic uncertainty & sensitivity study • Background estimation

17. RENO Detector total ~460 tons

18. RENO Detector

19. Electronics • Use SK new electronics (will be ready in Sep., 2008)

20. Source Driving System

21. Prototype Detector Assembly Acrylic vessels Inner acrylic vessel Mounting PMTs Nitrogen flushing of LS assembled prototype Filling with liquid scintillator

22. Mockup Detector Target + Gamma Catcher Acrylic Containers (PMMA: Polymethyl Methacrylate or Plexiglass) Buffer Stainless Steel Tank

23. MC of Mockup Detector 60Co 137Cs

24. 0.1% Gd compounds with CBX (Carboxylic acids; R-COOH) - CBX : MVA (2-methylvaleric acid), TMHA (2-methylvaleric acid) Gd Loaded Liquid Scintillator • Recipe of Liquid Scintillator : • Recipe with various mixture: performance (light yield, transmission & attenuation lengths), availability, cost, etc. • Design of purification system & flow meter • Long-term stability test • Reaction with acrylic? • R&D on LAB

25. precipitation Synthesis of Gd-carboxylate Rinse with 18MΩ water Dryer

26. R&D with LAB CnH2n+1-C6H5 (n=10~14) Light yield measurement • High Light Yield : not likely Mineral oil(MO) • replace MO and even Pseudocume(PC) probably • Good transparency (better than PC) • High Flash point : 147oC (PC : 48oC) • Environmentally friendly (PC : toxic) • Components well known (MO : not well known) • Domestically available:Isu Chemical Ltd. (이수화학) PC100% LAB100% PC40% PC20% LAB100% PC20% N2 LAB60% LAB80% MO80%

27. LAB : (C6H5)CNH2N+1 C16H26 C17H28 C18H30 C19H32 7.17% 27.63% 34.97% 30.23% # of H [m-3] = 0.631 x 1029 H/C = 1.66 Measurement of LAB Components with GC-MS

28. 4 MeV(KE) e+ y sy (mm) |y| Evis (MeV) 1 MeV (KE) e+ PMT coverage, resolution ~210 photoelectrons per MeV visible energy Reconstruction : vertex & energy • Reconstructed vertex:~8cm at the center of the detector • Energy response and resolution:

29. time pulse height OD PMTs A ~140cm Veto (OD) B ~40cm Buffer (ID) target ID PMTs g-catcher buffer C ~120cm D Reconstruction of Cosmic Muons

30. Calculation of Background Rates due to Radioactivity

31. Calculation of Muon Rate at the RENO Underground Muon intensity at the sea level using modified Gaisser parametrization + MUSIC or Geant4 (the code for propagating muon through rock)

32. Systematic Errors

33. New!! (full analysis) RENO Expected Sensitivity 10x better sensitivity than current limit

34. SK Dm2 GLoBES group workshop@Heidelberg – Mention’s talk

35. Status Report of RENO • RENO is suitable for measuring q13 (sin2(2q13) > 0.02) • Geological survey and design of access tunnels & detector cavities are completed → Civil construction will begin in early June, 2008. • RENO is under construction phase. • Data –taking is expected to start in early 2010. • TDR will be ready in June of 2008. • International collaborators are being invited.