Jee-Seung Jang for the RENO collaboration, GISTInternational Workshop on RENO-50 toward Neutrino Mass HierarchSNU, June 13-14, 2013

Contents Introduction to RENO (Reactor Experiment of Neutrino Oscillations) Status of RENO Improvements in data analysis & the last results Future plan and Summary

q13 Measurement in Reactor Experiment* The Disappearance of Reactor Electron Antineutrino

(12 institutions and 40 physicists) Chonbuk National University Chonnam National University Chung-Ang University Dongshin University Gyeongsang National University Kyungpook National University Pusan National University Sejong University Seokyeong University Seoul National University Seoyeong University Sungkyunkwan UniversityRENO Collaboration Total cost : $10M Start of project : 2006The experiment is running with both near & far detectors from Aug. 2011

RENO Experimental SetupTotal average thermal output ~16.4 GWth 120 m.w.e.450 m.w.e.

Detection of Reactor Antineutrinos* Inverse beta decay (IBD) Neutrino energy measurement

354, 10 Inner PMTs ( 14 % surface coverage ) 67, 10 Outer PMTs

ExperimentsLocationThermal Power(GW)Flux Weighted BaselinesNear/Far (m)DepthNear/Far(mwe)Target Mass(tons)Statisticsper year(GWtonyr)Double ChoozFrance8.5[410/1050]120/3008.6/8.673RENOKorea16.7409/1444120/45016/16267Daya BayChina17.4470(576)/1648250/860402/801392

Summary of Detector ConstructionTunnel excavationDetector structure & buffer steel tanks competedAcrylic containers installedPMT test & installationDetector closing, installation of electronics & Dry runLiquid scintillator production & fillingStart data taking

20082009201020116116168

Neutrino Target(Gd+LS)Gamma Cather (LS)Buffer(Mineral Oil)VETO (Water)

Water filling for Veto Both near and far detectors are filled with Gd-LS, LS & mineral oil as of July 5, 2011.Veto water filling was completed at the end of July, 2011.

Recipe of Liquid Scintillator(to satisfy chemical, physical, optical properties, and safety requirements)

CnH2n+1-C6H5 (n=10~14)Gd Loaded Liquid Scintillator

Aromatic Solvent & FlourWLSGd-compoundLABPPO +Bis-MSB0.1% Gd+(TMHA)3(trimethylhexanoic acid)

Stability of Gd Concentration* Stable light yield : ~250 pe/MeV * Stable transparency at 430 nmNuclear Instruments and Methods in Physics Research A, 707, 45-53 (2013. 4. 11)

Software Trigger High DAQ efficiencySoftware trigger selects the events specified by using the timing information in each hit-data cell

timeEvent# (N-1)Event# NEvent# (N+1)17usecPeriodic Trigger

RENO Status Data taking began on Aug. 1, 2011 with both near and far detectors. (DAQ efficiency : ~95 %)A (220 days) : First q13 result [11 Aug, 2011~26 Mar, 2012] PRL 108, 191802 (2012)C (~700 days) : Shape+rate analysis (in progress) [11 Aug, 2011~31 Jul, 2013]B (403 days) : Improved q13 result [11 Aug, 2011~13 Oct, 2012] NuTel 2013Absolute reactor neutrino flux measurement in progress [reactor anomaly & sterile neutrinos]B (403 days) : Improved q13 result [11 Aug, 2011~13 Oct, 2012] NuTel 2013

Improvements in the Data Analysis

Statistics : -- about twice more data

Systematics : -- Improved background estimation/reduction (Li/He background, fast N, flasher events) -- Improved energy scale calibration

Energy Scale Calibration

Energy Scale CalibrationWe found a good calibration function for reactor energy scale.

Prompt signal (e+) : 1 MeV 2gs + e+ kinetic energy (E = 1~10 MeV) Delayed signal (n) : 8 MeV gs from neutrons capture by Gd

~26 ms (0.1% Gd) in LSSignature of Reactor Neutrino Event (IBD)Observed spectra for Prompt Signalm212 = 7.6x10-5sin2(212) = 0.8556m213 = 2.32x10-3sin2(213) = 0.113

Observed Spectra for Delayed Signal (n captured by Gd)

Detector Stability

Backgrounds Accidental coincidence between prompt and delayed signals Fast neutrons produced by muons, from surrounding rocks and inside detector (n scattering : prompt, n capture : delayed) 9Li/8He b-n followers produced by cosmic muon spallation

9Li/8He Background 9Li/8He are unstable isotopes emitting (b,n) followers and produced when a muon interacts with carbon in the LS. 9Li/8HeIBD

Background Spectra Background shapes and rates are well understood Total backgrounds : 6.5% at Far 2.7% at Near

Summary of Final Data Sample(Prompt energy < 10 MeV)

Expected Reactor Antineutrino Fluxes Reactor neutrino flux - Pth : Reactor thermal power provided by the YG nuclear power plant - fi : Fission fraction of each isotope determined by reactor core simulation of Westinghouse ANC - fi(En) : Neutrino spectrum of each fission isotope [* P. Huber, Phys. Rev. C84, 024617 (2011) T. Mueller et al., Phys. Rev. C83, 054615 (2011)] - Ei : Energy released per fission [* V. Kopeikin et al., Phys. Atom. Nucl. 67, 1982 (2004)]

Observed Daily IBD Rate Solid line is predicted rate from the neutrino flux calculation. Observed points have very good agreement with prediction. A new way to measure the reactor thermal power remotely!!!Reactor OFF

A clear deficit in rate (7 % reduction) Consistent with neutrino oscillation in the spectral distortionReactor Antineutrino Disappearance

Definite Measurement of Sin22q13 1st result(PRL)New result

RENOs Projected Sensitivity of q13 (5.6 s) (402 days)(18 % precision)

RENO measured the q13 successfully and stable data taking exceeded 600 days.RENO improved the systematic uncertainties and energy calibration after publication of the first result. -- The clear disappearance of the reactor antineutrinos.

-- New result with 5.6 s

SummaryRENO is preparing a new result based on shape analysis.RENO projects 3 years of data to improve the sensitivity of q13 measurement.

Thank you !

& Enjoy the conference and Seoul !

Comparison of Observed SpectraFinally, we can compare the number of rector anti-neutrino eventsobserved in our detector with the expectation from the reactor.

Detection Efficiency & Systematic Uncertainties

Cf Contamination Tiny fraction of Cf calibration source dissolved into Gd-LS after Oct. 13, 2012 : - Loose O-ring in the source container LS into the container Cf out of its disc package Cf contamination on gloves Cf contamination on the container surface & dissolved into LS - Cf at the bottom of target (confirmed by event vertex)

Cf Contamination Removal by a multiplicity cut & estimation by its energy shape

Observed Daily IBD RateIt is the accurate flux measurement.New methods for remote monitoring of reactor.

Cf contamination

IBD Prompt Signal (Data vs. MC)

***6 reactors are lined up in roughly equal distances and span ~1.3 km

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