The energy calibration for the solar neutrino analysis of all three phases of the Sudbury Neutrino Observatory
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This work presents the calibration of the energy response of the Sudbury Neutrino Observatory (SNO). The development of the energy response processor RSP and its use in setting the energy scale of SNO and reconstructing the energy of neutrino-like events is presented for each of the three phases of SNO: the pure heavy water phase, the salt phase, and the neutral current detector (NCD) phase. A 16N calibration source, producing mainly 6.13 MeV γ-rays, is the primary energy calibration source. It is used to set the energy scale of the detector and to test for errors in the energy calibration and reconstruction process. The errors associated with energy reconstruction in the pure heavy water and salt phase data, that is to be used in a low energy threshold solar 8B neutrino analysis, are derived for the RSP energy response processor and shown to be in agreement with other analyses. The largest of the errors, that associated with using the 16N source to set the energy scale of the detector, is improved through a detailed and thorough analysis. The calibration of the energy scale of the photomultiplier tube array in the third phase, with an array of 3He proportional counters (NCDs) distributed within the heavy water, is presented. The event energy reconstruction errors in the NCD phase are reassessed with more precise measurements and shown to be in agreement with the conservative estimates used in the analysis SNO presented in 2008. The implications of the improvements in the error are assessed and the solar 8B neutrino fluxes—charged current (CC), elastic scattering (ES), and neutral current (NC)—are determined to be: φCC = 1.68+0.09−0.07, φES = 1.79+0.25-0.22, and φNC = 5.52+0.48-0.45, in units of 10^6/cm^2/s. The errors quoted are the combined statistical and systematic uncertainties. These results are in good agreement with the results published by SNO in 2008 with a modest improvement in the CC measurement.