Soo-Bong Kim Dept. of Physics & Astronomy Seoul National University April 15, 2009 A Korean Project of Neutrino Oscillations

Birth of Neutrino Total spin is not conserved, either… 14 C  14 N + e – spin 0 spin 1 spin 1/2 Bohr: Energy and momentum may not be conserved in  decay ?… F. A. Scott, Phys. Rev. 48, 391 (1935) Observed continuous  spectra Predicted discrete spectra 14 C  decay Physics in trouble with   decay Energy & momentum are not conserved

Wolfgang Pauli’s introduction of an imaginary particle (1931) Wolfgang Pauli’s introduction of an imaginary particle (1931) Neutrino : Undetectable massless neutral fermion (Weakly interacting) Neutrino

Neutrino: Elementary Particles  Elementary particles with almost no interactions  Almost massless: impossible to measure its mass  Universe full of neutrinos

Tiny Neutrino Masses E=mc 2 mass kg kg kg SM GUT

Mixing Angles (  12,  23,  13 ) Unmeasured yet Oscillating Neutrinos  Three flavors of neutrinos repeat transformation among them as time goes by. Discovery of Neutrino Oscillations (1998) CKM Quark Mixing and CP Violation

Properties of Neutrinos  Almost no interaction with matter (via weak interaction only)  Mass is too small to measure  Elementary particles with three flavors ( e, ,  )  Transformation among the three flavors  Universe full of neutrinos (330 per 1cm 3 )

Why is the neutrino physics so improtant? Neutrino Oscillation and Mass Window for New Physics ! Origin of Our Universe !! Neutrinos are hot !

1 2    Neutrino Oscillation 1 2 m1m1 m2m2 Flavor statesMass states neutrino oscillations due to wave property of neutrino 2 1    2-Neutrino Oscillation

Oscillation Probability Neutrino energy Neutrino trajectory

Solar Neutrino( e ) Oscillations Nuclear fusion : 4p → 4 He + 2e e + thermal energy  Deficit of solar neutrinos → Evidence for oscillations - Homestake (Cℓ, 1968~1993): first measurement - Kamiokande (H 2 O, 1986~1993): energy/directionality - SAGE & GALLEX/GNO (Ga, 1990~2001) - Super-Kamiokande (H 2 O, 1996~ ): precision exp.  Discovery of Solar Neutrino Oscillations - SNO (D 2 O, 2002): detect  /  ( e →  &  )  Confirmation of Solar Neutrino Oscillations - KamLAND (2002): reactor neutrino oscillation  12 측정 )

Atmospheric Neutrino(  ) Oscillations Cosmic ray (p, He, …) + Atmosphere →  /K meson →  → e +   Discovery of atmospheric neutrino oscillations (  →  ) - Super-Kamiokande (1998) - measurement of  23  Confirmation of atmospheric neutrino oscillations - K2K (2004) : accelerator beam  (250km) - MINOS CNGS (2006) : ~700km  23 측정 )

Summary of Neutrino Oscillation Parameters  23  12  13  m 12 2 = 7.9(  5% )  eV 2  m 23 2 = 2.4(  13% )  eV 2 ≈  m 13 2  mass difference : sin 2  12 = 0.31(  9%) sin 2  23 = 0.44( +20 –11 % ) sin 2  13 < 0.17 (90% C.L.)  mixing angles :

Precision Measurement of Neutrino Oscillation Parameters U e3 (New field of particle physics open!) 0  reactor and accelerator  13 = ? atmospheric SK, K2K  23 = ~ 45° Large and maximal mixing! (atmospheric neutrinos & neutrino beams) SNO, solar SK, KamLAND  12 ~ 32° (Solar neutrinos & reactor neutrinos) ?  CP : CP phase

 13 from Reactor and Accelerator Experiments - Clean measurement of  13 - No matter effects CP violation mass hierarchy matter * Reactor * Accelerator - sin 2 2  13 is a missing key parameter for any measurement of  CP

Nuclear Power Plants Reactor Neutrinos 영광영광 울진울진  인체에 유해한 방사능 ( 중성자, 알파선, 베타선, 감마선 ) 은 원자로 내부에서 차폐됨  핵붕괴시 방출되는 중성미자는 물질과 거의 반응을 하지 않으므로 인체에 무해하며 원자로를 빠져 나와서 사방으로 끊임없이 퍼져 나감 ( 매초당 ~10 17 /m 2 방출 )  영광발전소는 열생산 최대용량이 17GW 로서 세계 2 위의 강력한 중성미자 방출원임

Energy Spectra of Reactor Neutrinos

Detection Method of Reactor Neutrinos (Reines & Cowan, 1957)

(2) 5<E delayed <11MeV n capture energy Detection of Reactor Neutrinos (1) 0.7<E prompot <9MeV e + energy

Chooz:  13 <13 0 RENO (  13 ) KamLAND (  12 ) Reactor Neutrino Experiments

New Reactor Neutrino Experiment (  13 )  Need identical detectors to reduce the systematic errors in 1% level  Detectors should be at underground to reduce the cosmic-ray backgrounds  Find disappearance of e fluxes due to neutrino oscillation as a function of energy using multiple, identical detectors

Oscillation Parameters from Reactor Neutrinos L~50km: accurate sin 2 2  12 sin 2 2  13 =0.1, E =4MeV L~1.5km: pure sin 2 2  13 L~5km:  m 2 13 Scope of RENO Project L~180km KamLAND: accurate  m 2 12 moderate  12 3  RENO   

Reduction of Reactor Neutrinos due to Oscillations  sin 2 2  13 > 0.01 with 10 t 14GW 3yr ~ 400 tGWyr (400 tGWyr: a 10(40) ton far detector and a 14(3.5) GW reactor in 3 years) Disappearance Reactor neutrino disappearance Prob. due to  13 with the allowed 2  range in  m 23 2

Double-CHOOZ (France) * Proposal (June 20, 2006) : hep-ex/ Double-Chooz Collaboration: France, US, Germany, Italy, Japan, England, Brasil, Spain & Russia * 2010 년 근거리 / 원거리검출기 동시 가동

Daya Bay (China) * Proposal to DOE (Jan. 15, 2007): hep-ex/ Daya Bay Collaboration: China, US, Czech Republic, Hong Kong, Russia & Taiwan

ExperimentLocation Thermal Power (GW) Detector Locations Near/Far (m) Depth Near/Far (mwe) Target Near/Far (tons) Double-CHOOZFrance8.7280/105060/30010/10 RENOKorea / /45016/16 Daya BayChina (500)/1985(1613)260/  2/80 World Competition in the Reactor Neutrino Experiments

 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) RENO Collaboration

RENO Experimental Setup

Google Satellite View of YongGwang Site

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

Schedule for RENO Construction Activities Detector Design & Specification Geological Survey & Tunnel Design Detector Construction Detector Commissioning Detector construction Tunnel excavation

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

 Mixing & Supplying Liquid Scintillators  Data Acquisition System

Mockup Detector Event Display Real time display: Online monitoring tool Basic information on histograms PMT hit display

 RENO Detector Design and Specification RENO Detector

 Structure design completed (’08. 12)

PMT test completed & under purchase

 Use SK new electronics  광센서의 신호를 초고속 처리하는 ASIC 을 사용한 데이터 수집 장비 DAQ Electronics completed (’08. 11)

 Mixing for 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) 합성 연구 : - CBX : TMHA (trimethylhexanoic acid), MVA (2-methylvaleric acid) R&D of Gd Loaded Liquid Scintillator  LAB(Linear Alkyl Benzene) Properties : C n H 2n+1 -C 6 H 5 (n=10~14) Light yield measurement PC100% LAB100% PC40% PC20% LAB100% PC20% N2 LAB60% LAB80% MO80%

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 ) PC 와 Mineral oil/Dodecane 대용으로 사용할 수 있는 LAB(Linear Alkylbenzene) 의 분자 구조식

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

Raw/MCDataProductionModulesReconstructionModulesUserAnalysisModulesUserntuples RACFrameWork default modules data input and output, database access for run configuration and calibration Has talk-to function for changing input parameters without recompiling Addition of modules by user Modules can be set as filter module for selecting events Easy to use and build in RENO software environment R Analysis Control RENO Analysis Control

Inverse Beta Decay Cosmic Muon RENO Event Display

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

 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 +

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

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