Data release accompanying the 2nd KamLAND Reactor Result


"Measurement of Neutrino Oscillation with KamLAND: Evidence of Spectral Distortion"
by the KamLAND Collaboration (T. Araki et al.). Jun 2004. 5pp.

Paper  |  PostScript  |  PDF  |

Proper reference for the data given below:

KamLAND collaboration, Phys.Rev.Lett.94:081801,2005

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Event List

The following data file lists the prompt energies of the 258 observed neutrino candidate events.
The event energies are in MeV and show the positron energy including the annihilation energy (0 MeV kinetic energy positron appears as 1.022 MeV).

Event list  |  plain text  |

Also monthly candidate events are listed, the monthly candidates are separated by #, the second column is year/month, and the third column is the monthly detector livetime (sec.).

Monthly event list  |  plain text  |

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Background Spectrum

The following data file provides the estimated energy spectra for He8/Li9 events, accidental coincidences and C13(α,n) background events and are given in arbitrary units. The first column is the mid-point of the energy bin using the positron energy scale, the second column is the He8/Li9 background rate in that bin, the third is the accidental background rate and the fourth is the C13(α, n) expected rate. The background spectra below 2.6 MeV are still preliminary.
The total (integrated) backgrounds above 2.6 MeV have to be normalized to 4.8, 2.69 and 10.3 events, respectively, as given in the paper.
The beta-delayed neutron energy spectrum of the He8/Li9 background is not known very well and only a few of the beta-decay branches are modeled here.

Background spectrum  |  plain text  |

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Number of Fissions

The figure shows the integrated fission flux at the Kamioka site for the four main nuclei that have fission products contributing to the anti-neutrino flux from reactors up to a distance of 1000km from the experimental site. The four main fission nuclei are U-235, U-238, Pu-239 and Pu-241 and their fission fluxes, integrated over the total detector livetime, are provided in the data file below. The total fission fluxes when including all reactors up to 1000km are 1.2055e13, 1.6864e12, 6.4194e12 and 1.2143e12 fissions/cm2, respectively.
Neutrino spectra for the 4 fissile nuclei can be obtained from K.Schreckenbach et al., Phys.Lett. B 160, 325 (1985) for U235, A.A.Hahn et al., Phys.Lett.B 218, 365 (1989) for Pu239,Pu241 and P.Vogel et al., Phys.Rev.C 24, 1543 (1981) for U238.
For a more precise calculation, consideration of long-lived nuclei is necessary. See for example the calculation by V.I.Kopeikin et al., Physics of Atomic Nuclei 64, 849 (2001).

Fission flux  |  plain text  |

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χ2 Map

The following file gives the χ2 map from the KamLAND rate+shape analysis. The minimum χ2 is 701.357 at (tan2θ, Δm2)=(0.457, 7.943×10-5).

χ2 Map  |  plain text  |




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Other Relevant Constants

Some numbers necessary for calculating expected number of neutrino events are given here.

Total live time after spallation cut 515.1 days
Total number of target protons in the 5.5-m-radius fiducail volume 4.61e31
Approximated energy resolution data
The analysis threshold to the positron energy 2.6 MeV
Total detection efficiency 89.8%
Total systematic uncertainty on number of neutrino events 6.5%

For a comparison, number of events for no oscillation from detailed calculation of KamLAND group is 365.2±23.7(syst.) events.

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