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Estimated theta13 measurement at RENO

전은주 , 강운구 , 김영덕 , 마경주 ( 세종대학교 ),공대정 , 김동희 , 김우영 , 사무엘스테파냔 , 서준석 , 아딜 칸 ,안드레이 김 ( 경북대학교 ), 박인곤 ( 경상대학교 ), 박명렬 ( 동신대학교 ), 안정근 , 이효상 ( 부산대학교 ), 김수봉 , 김현수 , 박강순 , 박정식 , 신경하 , 이재승 , 최선호 , 황원석 ( 서울대학교 ),권은향 , 김동현 , 박차원 , 백승록 , 유인태 , 최수용 , 최영일 (성균관대학교 ),김성현 , 김재률 , 주경광 , 임인택 , 장지승 , 정신석 ( 전남대학교 ), 오영도 ( 포항공과대학교 ),N.Danilov,YU.Krylov,G.Novikova,E.Yanovich (INR and IPCE, Russia)

KPS 한국물리학회Apr. 18, 2008

Outline

What is RENO? Detector design Background estimation Systematic uncertainty Sensitivity Summary

Distance

Pro

babi

lity

ν e

1.0

EEνν <10 MeV10 MeV

1200 to 1800 meters

Unoscillated flux Unoscillated flux observed hereobserved here

Well understood, isotropic source Well understood, isotropic source of electron anti-neutrinosof electron anti-neutrinos Oscillations observed Oscillations observed

as a deficit of as a deficit of ννee

sinsin2222θθ1313

)/27.1(sin θ2sin1)νν( ν213

213

2 ELmP ee Survival ProbabilitySurvival Probability

e

ee

Determination of 13 using e from reactors

e

ee

E<10 MeV

Inverse Beta Decay enpe

νe

Gd

γ

γ γ

γ

30μs

p

e+γ

γ

prompt signal

Delayed signaln

E ~8 MeV

Detection of neutrino events

8MeV30μs

1~8MeV

t

Signal Property

Schematic Setup of RENO at YongGwang

Inner Diameter (cm)

vessel Inner Height (cm)

Filled with Mass (tons)

Target Vessel 280 Acryl 320 Gd(0.1%) + LS 15.4

Gamma catcher 400 Acryl 440 LS 27.5

Buffer tank 540 Stainless steel 580 Mineral oil(LAB)

59.2

Veto tank 840 Steel 880 water 354.7

total ~450 tons

Four concentric cylindrical parts Identical detectors for near and far Target and gamma catcher are filled

with liquid scintillator aiming at detecting inverse beta decay

342 10-inch PMTs on the surface of buffer

67 10-inch PMTs on the VETO

RENO Detector

15 ton targets (=1.3x1030 protons)

Near Far

IBD events/yr 4.8x105 4.3x104

# of events/dayw/ 70% efficiency

920 82

target

buffer

-catcher

veto

7

Muon veto system

Cosmic muon induced neutron backgrounds:

•Fast neutrons from rock•Neutrons by untagged muons in

VETO•Beta-neutron cascades: muon

spallation on 12C 8He and 9Li 1.5m water VETO works also as neutron and gamma shielding.

Fast neutron rate < 1/day @ Far detectorBackground/signal < 1%

Vertical Depth

(m/mwe)

μ (m-2s-1)<Eμ> (GeV)

Far 165/437 0.85 65.2

Near 35/93 5.5 34.3

8

First-hit hit time

Number of photoelectrons

Buffer mounted PMTsVeto mounted PMTs

Event Info

Event Number

Log scale

Ne Radius

A

B

C

D

Veto(OD)

Buffer(ID)

Reconstruction of Cosmic Muons

Veto only

Buffer only

catcher+target

total

Gen. 3156 1571 1895 6622

Rec. (OD) (ID)

3028 15711571

18951895

6494 3466

No tagging 128 0 0

Tagging eff.

95.9% 100.0% 100.0%

Total number of events generated= 7300 Through-going muons= 6622

Through-going muon reconstruction using RENO-specific muon spectrum

angle(degree)

(Xtrue-Xrec)_OD_entrance

(Xtrue-Xrec)_OD_exit

(Xtrue-Xrec)_ID_entrance

(Xtrue-Xrec)_ID_exit

angle difference betweentracktrue and trackrec

rate from rock [Hz]

Double CHOOZ Daya Bay RENO

Rockcomposition

(K) 1.6 ppm (U) 2.00 ppm(Th) 5.0 ppm

(K) 5 ppm(U) 10 ppm(Th) 30 ppm

(K) 4.0 ppm(U) 4.8+/-1.8 ppm(Th) 6.0+/-2.2 ppm * Sample from

Chongpyung.

Detector DxH Size [cm]

230x246 (10.3 m3)

320x320 280x320

Shelding 17 cm Steel 2.5 m Water+ 0.45 m Oil

1.5 m Water

Rates (K)[Hz] (U) (Th)

0.86 ~0.89 0.98

0.26 0.65 2.6 (E>1 MeV)

0.210.531.74(E>0.5 MeV)

Total rate ~2.73 Hz 3.5 Hz 2.5 Hz

Calculation of Background at the RENO Underground

Summary of systematic errors

Systematic Source CHOOZ (%)

RENO (relative

(%))(Goal)

Reactor related absolute

normalization

Reactor antineutrino flux and cross section

1.9 < 0.1

Reactor power 0.7 0.2

Energy released per fission 0.6 < 0.1

Number of protons in target

H/C ratio 0.8 0.2

Target mass 0.3 < 0.1

Detector Efficiency

Positron energy 0.8 0.1

Positron geode distance 0.1 0.0

Neutron capture (H/Gd ratio)

1.0 < 0.1

Capture energy containment

0.4 0.1

Neutron geode distance 0.1 0.0

Neutron delay 0.4 0.1

Positron-neutron distance 0.3 0.0

Neutron multiplicity 0.5 0.05

combined 2.7 < 0.5

SK231m

Sensitivity

(rate only analysis)

SK231m

GLoBES group workshop@Heidelberg

– Mention’s talk

90%CL sensitivity after 3 years of data taking

Systematic analysis for RENO total systematic error: less than 0.5% as our goal

Most backgrounds are estimated. (< 1% B/S) sin2(213) = 0.02 sensitivity can be reached with 3 year

data.

Summary

Schedule

Activities

Detector Design& Specification

Geological Survey& Tunnel Design

DetectorConstruction

Excavation &Underground Facility

Construction

DetectorCommissioning

2006 2007 2008 20093 6 9 12 3 6 9 12 3 6 9 12 3 6 9 12

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