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Reactor electron antineutrino disappearance in the Double Chooz experiment

Y. Abe, C. Aberle, J. C. dos Anjos, J. C. Barriere, M. Bergevin, A. Bernstein, T. J. C. Bezerra, L. Bezrukhov, E. Blucher, N. S. Bowden, C. Buck, J. Busenitz, A. Cabrera, E. Caden, L. Camilleri, R. Carr, M. Cerrada, P. -J. Chang, P. Chimenti, T. Classen, A. P. Collin, E. Conover, J. M. Conrad, J. I. Crespo-Anadón, K. Crum, A. Cucoanes, M. V. D'Agostino, E. Damon, J. V. Dawson, S. Dazeley, D. Dietrich, Z. Djurcic, M. Dracos, V. Durand, J. Ebert, Y. Efremenko, M. Elnimr, A. Etenko, M. Fallot, M. Fechner, F. von Feilitzsch, J. Felde, D. Franco, A. J. Franke, M. Franke, H. Furuta, R. Gama, I. Gil-Botella, L. Giot, M. Goger-Neff, L. F. G. Gonzalez, M. C. Goodman, J. TM. Goon, D. Greiner, N. Haag, C. Hagner, T. Hara, F. X. Hartmann, J. Haser, A. Hatzikoutelis, T. Hayakawa, M. Hofmann, G. A. Horton-Smith, A. Hourlier, M. Ishitsuka, J. Jochum, C. Jollet, C. L. Jones, F. Kaether, L. N. Kalousis, Y. Kamyshkov, D. M. Kaplan, T. Kawasaki, G. Keefer, E. Kemp, H. de Kerret, Y. Kibe, T. Konno, D. Kryn, M. Kuze, T. Lachenmaier, C. E. Lane, C. Langbrandtner, T. Lasserre, A. Letourneau, D. Lhuillier, H. P. Lima, M. Lindner, J. M. López-Castanõ, J. M. LoSecco, B. K. Lubsandorzhiev, S. Lucht, D. McKee, J. Maeda, C. N. Maesano, C. Mariani, J. Maricic, J. Martino, T. Matsubara, G. Mention, A. Meregaglia, T. Miletic, R. Milincic, H. Miyata, Th. A. Mueller, Y. Nagasaka, K. Nakajima, P. Novella, M. Obolensky, L. Oberauer, A. Onillon, A. Osborn, I. Ostrovskiy, C. Palomares, I. M. Pepe, S. Perasso, P. Perrin, P. Pfahler, A. Porta, W. Potzel, J. Reichenbacher, B. Reinhold, A. Remoto, M. Rohling, R. Roncin, S. Roth, Y. Sakamoto, R. Santorelli, F. Sato, S. Schonert, S. Schoppmann, T. Schwetz, M. H. Shaevitz, S. Shimojima, D. Shrestha, J. -L. Sida, V. Sinev, M. Skorokhvatov, E. Smith, J. Spitz, A. Stahl, I. Stancu, L. F. F. Stokes, M. Strait, A. Stuken, F. Suekane, S. Sukhotin, T. Sumiyoshi, Y. Sun, R. Svoboda, K. Terao, A. Tonazzo, M. Toups, H. H. Trinh Thi, G. Valdiviesso, C. Veyssiere, S. Wagner, H. Watanabe, B. White, C. Wiebusch, L. Winslow, M. Worcester, M. Wurm, F. Yermia, V. Zimmer

TL;DR

This work measures the reactor electron antineutrino disappearance at a 1050 m baseline to determine the neutrino mixing parameter θ_{13} using a rate+spectral-shape analysis. The analysis relies on a comprehensive detector model, extensive calibrations, and detailed reactor flux predictions anchored to the Bugey4 result, enabling a precise extraction of sin^2 2θ_{13} from both the observed rate and the prompt-energy spectrum. The final result, sin^2 2θ_{13} = 0.109 ± 0.030(stat) ± 0.025(syst), with Δm^2_{31} fixed to 2.32×10^{-3} eV^2, excludes the no-oscillation hypothesis at 99.8% CL (2.9σ). The analysis demonstrates a clear energy-dependent oscillation signal that is consistent with other leading measurements and showcases the value of spectral information in reactor neutrino experiments.

Abstract

The Double Chooz experiment has observed 8,249 candidate electron antineutrino events in 227.93 live days with 33.71 GW-ton-years (reactor power x detector mass x livetime) exposure using a 10.3 cubic meter fiducial volume detector located at 1050 m from the reactor cores of the Chooz nuclear power plant in France. The expectation in case of theta13 = 0 is 8,937 events. The deficit is interpreted as evidence of electron antineutrino disappearance. From a rate plus spectral shape analysis we find sin^2 2θ13 = 0.109 \pm 0.030(stat) \pm 0.025(syst). The data exclude the no-oscillation hypothesis at 99.8% CL (2.9σ).

Reactor electron antineutrino disappearance in the Double Chooz experiment

TL;DR

This work measures the reactor electron antineutrino disappearance at a 1050 m baseline to determine the neutrino mixing parameter θ_{13} using a rate+spectral-shape analysis. The analysis relies on a comprehensive detector model, extensive calibrations, and detailed reactor flux predictions anchored to the Bugey4 result, enabling a precise extraction of sin^2 2θ_{13} from both the observed rate and the prompt-energy spectrum. The final result, sin^2 2θ_{13} = 0.109 ± 0.030(stat) ± 0.025(syst), with Δm^2_{31} fixed to 2.32×10^{-3} eV^2, excludes the no-oscillation hypothesis at 99.8% CL (2.9σ). The analysis demonstrates a clear energy-dependent oscillation signal that is consistent with other leading measurements and showcases the value of spectral information in reactor neutrino experiments.

Abstract

The Double Chooz experiment has observed 8,249 candidate electron antineutrino events in 227.93 live days with 33.71 GW-ton-years (reactor power x detector mass x livetime) exposure using a 10.3 cubic meter fiducial volume detector located at 1050 m from the reactor cores of the Chooz nuclear power plant in France. The expectation in case of theta13 = 0 is 8,937 events. The deficit is interpreted as evidence of electron antineutrino disappearance. From a rate plus spectral shape analysis we find sin^2 2θ13 = 0.109 \pm 0.030(stat) \pm 0.025(syst). The data exclude the no-oscillation hypothesis at 99.8% CL (2.9σ).

Paper Structure

This paper contains 33 sections, 15 equations, 17 figures, 7 tables.

Table of Contents

  1. Introduction
  2. Detector and Method Description
  3. Overview
  4. Radiopurity
  5. Double Chooz Liquids
  6. ID Photomultiplier Tubes
  7. The Inner Veto
  8. Electronics and Data Acquisition
  9. The Outer Veto
  10. Calibration Systems
  11. Reactor and Detector Models
  12. Thermal Power
  13. Mean Cross Section per Fission
  14. Fission Rate Computation
  15. Bugey4 Normalization and Antineutrino Rate Calculation
  16. ...and 18 more sections

Figures (17)

  • Figure 1: A cross-sectional view of the Double Chooz detector system.
  • Figure 2: Average target detector response evolution in time, as measured by the mean energy of the Gd-capture peak arising from interaction of spallation neutrons in the NT.
  • Figure 3: Block diagram of the Double Chooz readout and DAQ systems.
  • Figure 4: Demonstration of the linear PE calibration for one channel. The gain versus charge is shown. The dashed line highlights the constant component (linear behavior) of the gain observed at large charges. The calibration parametrizes this curve to correct the non-linear component (deviation from constant) of the gain, making the PE corrected energy scale linear to within 2%.
  • Figure 5: Detector calibration map, in cylindrical coordinates ($\rho$,$z$), as sampled with spallation neutrons capturing in H across the ID. Response variations are quantified as the fractional response with respect to the detector center. Largest deviation in NT are up to $5$%. A similar map is constructed with MC for calibration of its slightly different response uniformity pattern.
  • ...and 12 more figures