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

New Reactor Neutrino  13 Experiment  Lower background - Improved detector design - Increased overburden  CHOOZ : R osc = 1.01 ± 2.8% (stat) ± 2.7% (syst)  Larger statistics - More powerful reactors (multi-core) - Larger detection volume - Longer exposure  Smaller experimental errors - Identical multi detectors → Obtain ~1% precision !!!

Detection of Reactor Neutrinos data from CHOOZ hep-ex/ v1 (1) 0.7<E prompot <9MeV (2) 5<E delayed <11MeV (3) 1μs<ΔT <200μs e + energy n capture energy

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) +++

Schematic Setup of RENO at YeongGwang

Google Satellite View of YeongGwang Site

Schematic View of Underground Facility 100m300m 70m high 200m high 1,380m290m Far Detector Near Detector Reactors

Schedule Activities Detector Design & Specification Geological Survey & Tunnel Design Detector Construction Excavation & Underground Facility Construction Detector Commissioning

Comparison of Reactor Neutrino Experiments ExperimentsLocation Thermal Power (GW) Distances Near/Far (m) Depth Near/Far (mwe) Target Mass (tons) Double-CHOOZFrance8.7280/105060/30010/10 RENOKorea / /45016/16 Daya BayChina (500)/1985(1613)260/  2/80

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.

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

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

Stress analysis for tunnel design

Detector Design with MC Simulation  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  Systematic uncertainty & sensitivity study  Reconstruction(vertex position & energy) program written  Background estimation  RENO-specific MC simulation based on GLG4sim/Geant4 → Detailed detector design and drawings are completed

RENO Detector Inner Diameter (cm) Inner Height (cm) Filled withMass (tons) Target Vessel Gd(0.1%) + LS 16.5 Gamma catcher LS30.0 Buffer tank Mineral oil 64.4 Veto tank water352.6 total ~460 tons

RENO Detector

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

Source Driving System

Prototype Detector Assembly Acrylic vesselsInner acrylic vessel Nitrogen flushing of LS Mounting PMTs Filling with liquid scintillator assembled prototype

Mockup Detector Target + Gamma Catcher Acrylic Containers (PMMA: Polymethyl Methacrylate or Plexiglass) TargetDiameter61 cm Height60 cm Gamma Catcher Diameter120 cm Height120 cm BufferDiameter220 cm Height220 cm Buffer Stainless Steel Tank

MC of Mockup Detector 60 Co 137 Cs

Gd Loaded 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  Recipe of Liquid Scintillator : Aromatic SolventFlourWLSGd-compound LABPPO, BPO Bis-MSB, POPOP 0.1% Gd+TMHA (trimethylhexanoic acid)  0.1% Gd compounds with CBX (Carboxylic acids; R-COOH) - CBX : MVA (2-methylvaleric acid), TMHA (2-methylvaleric acid)

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

R&D with LAB Light yield measurement PC100% LAB100% PC40% PC20% LAB100% PC20% N2 LAB60% LAB80% MO80% C n H 2n+1 -C 6 H 5 (n=10~14) High Light Yield : not likely Mineral oil(MO) replace MO and even Pseudocume(PC) probably Good transparency (better than PC) High Flash point : 147 o C (PC : 48 o C) Environmentally friendly (PC : toxic) Components well known (MO : not well known) Domestically available: Isu Chemical Ltd. ( 이수화학 )

Measurement of LAB Components with GC-MS C 16 H 26 C 17 H 28 C 18 H 30 C 19 H % 27.63% 34.97% 30.23% LAB : (C 6 H 5 )C N H 2N+1 # of H [m -3 ] = x H/C = 1.66

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

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

Calculation of Background Rates due to Radioactivity Concentration 40 K (ppb) Concentration 232 Th (ppb) Concentration 238 U (ppb) 40 K [Hz] 232 Th [Hz] 238 U [Hz] Total [Hz] Rock4.33(ppm)7.58(ppm)2.32(ppm) LS in Target Target Contatiner LS in Gamma Catcher Gamma Catcher Container LS in Buffer ~ Buffer Tank PMT Total~24

J μ [cm -2 s -1 ] [GeV] Far 250 m2.9× m8.5× Near70 m5.5× Muon intensity at the sea level using modified Gaisser parametrization + MUSIC or Geant4 (the code for propagating muon through rock) Calculation of Muon Rate at the RENO Underground

Systematic Errors Systematic SourceCHOOZ (%)RENO (%) Reactor related absolute normalization Reactor antineutrino flux and cross section 1.9< 0.1 Reactor power0.7< 0.1 Energy released per fission0.6< 0.1 Number of protons in target H/C ratio Target mass0.3< 0.1 Detector Efficiency Positron energy Positron geode distance Neutron capture (H/Gd ratio)1.0< 0.1 Capture energy containment Neutron geode distance Neutron delay Positron-neutron distance Neutron multiplicity combined2.7< 0.6

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

GLoBES group – Mention’s talk SK  m 2

Status Report of RENO  RENO is suitable for measuring  13 (sin 2 (2  13 ) > 0.02)  RENO is under construction phase.  Geological survey and design of access tunnels & detector cavities are completed → Civil construction will begin in early June,  International collaborators are being invited.  TDR will be ready in June of  Data –taking is expected to start in early 2010.