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RENO and the Last Result

RENO and the Last Result. Jee-Seung Jang for the RENO collaboration, GIST International Workshop on RENO-50 toward Neutrino Mass Hierarch SNU, June 13-14, 2013. Contents. Introduction to RENO ( R eactor E xperiment of N eutrino O scillations) Status of RENO

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RENO and the Last Result

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  1. RENO and the Last Result Jee-Seung Jang for the RENO collaboration, GIST International Workshop on RENO-50 toward Neutrino Mass Hierarch SNU, June 13-14, 2013

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

  3. YongGwang (靈光) : ~250 km from Seoul q13Measurement in Reactor Experiment * The Disappearance of Reactor Electron Antineutrino Daya Bay Double Chooz RENO

  4. RENO Collaboration (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 University • Total cost : $10M • Start of project : 2006 • The experiment is running with both near & far detectors from Aug. 2011

  5. RENO Experimental Setup 120 m.w.e. Near Detector Total average thermal output ~16.4 GWth 290m 1380m Far Detector 450 m.w.e.

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

  7. RENO Detector (Gd loaded liquid scintillation detector) • 354, 10” Inner PMTs • ( 14 % surface coverage ) • 67, 10” Outer PMTs

  8. Summary of Detector Construction Tunnel excavation Detector structure & buffer steel tanks competed Acrylic containers installed PMT test & installation Detector closing, installation of electronics & Dry run Liquid scintillator production & filling Start data taking

  9. Finishing the Detector Installation(2011.1) VETO (Water) Buffer(Mineral Oil) Gamma Cather (LS) Neutrino Target (Gd+LS)

  10. Liquids Filling (2011.6) Gd-LS filling for Target • 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. Water filling for Veto LS filling for Gamma Catcher Gd Loaded Liquid Scintillator

  11. Gd Loaded Liquid Scintillator • Recipe of Liquid Scintillator • (to satisfy chemical, physical, optical properties, and safety requirements) CnH2n+1-C6H5 (n=10~14)

  12. Stability of Gd Concentration * Stable light yield : ~250 pe/MeV Nuclear Instruments and Methods in Physics Research A, 707, 45-53 (2013. 4. 11) * Stable transparency at 430 nm * Stable Gd concentration (0.11%)

  13. RENO Electronics QBEE developed by ICRR for Super-K (QTC Based Electronics w/ Ethernet) Software Trigger  High DAQ efficiency Software trigger selects the events specified by using the timing information in each hit-data cell • 24 channel input • 60MHz clock • 0.1pC, 0.52nsec resolution • ~2500pC/ch large dynamic range • No dead time (w/o hardware trigger) • Fast data transfer via Ethernet R/W 17usec Periodic Trigger time Event# N Event# (N+1) Event# (N-1)

  14. RENO Status Near • 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) A • B (403 days) : Improved q13 result • [11 Aug, 2011~13 Oct, 2012] • NuTel 2013 • B (403 days) : Improved q13 result • [11 Aug, 2011~13 Oct, 2012] • NuTel 2013 Far • C (~700 days) : Shape+rate analysis • (in progress) • [11 Aug, 2011~31 Jul, 2013] B • Absolute reactor neutrino flux measurement in progress • [reactor anomaly & sterile neutrinos] C

  15. 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

  16. Energy Scale Calibration Ge 68 (1,022 keV) Co 60 (2,506 keV) Cf 252 Cf 252 (2.2/7.8 MeV) (2.2/8.0 MeV)

  17. Energy Scale Calibration Far Detector Near Detector We found a good calibration function for reactor energy scale.

  18. Signature of Reactor Neutrino Event (IBD) • Prompt signal (e+) : 1 MeV 2g’s + e+ kinetic energy (E = 1~10 MeV) • Delayed signal (n) : 8 MeV g’s from neutron’s capture by Gd • ~26 ms (0.1% Gd) in LS Observed spectra for Prompt Signal Δm212 = 7.6x10-5 sin2(2θ12) = 0.8556 Δm213 = 2.32x10-3 sin2(2θ13) = 0.113

  19. Observed Spectra for Delayed Signal (n captured by Gd)

  20. Detector Stability

  21. 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 Accidentals m Fast neutrons 9Li/8He b-n followers m m p g 9Li n n e Gd Gd Gd n

  22. 9Li/8He Background • 9Li/8He are unstable isotopes emitting (b,n) followers and produced when a muon interacts with carbon in the LS. 9Li/8He IBD

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

  24. Summary of Final Data Sample (Prompt energy < 10 MeV) 279787 30211 20.48± 2.13 4.89± 0.60 737.69± 2.58 70.13± 0.75 369.03 402.69 62.0± 0.014 71.4± 0.014 3.61± 0.05 0.60± 0.03 13.73± 2.13 3.61± 0.60 3.14± 0.09 0.68± 0.04

  25. 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)]

  26. Observed Daily IBD Rate Reactor OFF R2 R1 R5 R4 R6 R5 R3 R3+R5+R6 • 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!!!

  27. Reactor Antineutrino Disappearance • A clear deficit in rate • (7 % reduction) • Consistent with neutrino • oscillation in the spectral • distortion

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

  29. RENO’s Projected Sensitivity of q13 (5.6 s) (402 days) (~ 12 s) (3 years) (18 % precision) (8 % precision) • 3 years of data : ±0.008 (8% precision) • - statistical error : ±0.010 → ±0.006 • - systematic error : ±0.015 → ±0.005 2013. 3 (8 % precision)

  30. Summary • 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 • RENO is preparing a new result based on shape analysis. • RENO projects 3 years of data to improve the sensitivity of q13measurement.

  31. Thank you ! & Enjoy the conference and Seoul !

  32. Comparison of Observed Spectra Finally, we can compare the number of rector anti-neutrino events observed in our detector with the expectation from the reactor.

  33. Detection Efficiency & Systematic Uncertainties

  34. 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)

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

  36. Observed Daily IBD Rate Cf contamination It is the accurate flux measurement. New methods for remote monitoring of reactor.

  37. IBD Prompt Signal (Data vs. MC) Rb ???

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