A precise determination of the KamLAND energy scale

The energies of the n&d1;e 's measured by KamLAND are directly related to the energies of the positrons produced during the inverse beta-decay reaction n&d1;e + p → e+ + n. Since direct calibration of the positron energy scale is not possible, a detailed analysis of the energy scale of the deployed KamLAND gamma sources has been performed. This analysis uses models for scintillation light quenching, bremsstrahlung, and Cerenkov radiation production to describe the energy scale non-linearity. The positron energy scale has been estimated from the measured gamma energy scale with a 1-sigma error less than 0.3% for all positron kinetic energies less than 10 MeV. The energy scales found from this method are compared to previous energy scales used in reconstruction of the KamLAND data.