Abstract
The oscillation results published by the Double Chooz Collaboration in 2011 and 2012 rely on background models substantiated by reactor-on data. In this analysis, we present a background-model-independent measurement of the mixing angle θ13 by including 7.53 days of reactor-off data. A global fit of the observed antineutrino rates for different reactor power conditions is performed, yielding a measurement of both θ13 and the total background rate. The results on the mixing angle are improved significantly by including the reactor-off data in the fit, as it provides a direct measurement of the total background rate. This reactor rate modulation analysis considers antineutrino candidates with neutron captures on both Gd and H, whose combination yields sin2(2θ13)=0.102±0.028(stat.)±0.033(syst.). The results presented in this study are fully consistent with the ones already published by Double Chooz, achieving a competitive precision. They provide, for the first time, a determination of θ13 that does not depend on a background model.
Highlights
In this analysis, we present a backgroundmodel-independent measurement of the mixing angle θ13 by including 7.53 days of reactor-off data
The results presented in this study are fully consistent with the ones already published by Double Chooz, achieving a competitive precision
As this 2-Off sample provides the most precise determination of the total background rate in a model independent way, it is introduced in the RRM analysis in order to improve the results on θ13, which remains as the only free parameter in the fit
Summary
Three reactor neutrino experiments, Double Chooz [1], Daya Bay [2] and RENO, [3] have successfully determined the leptonic mixing angle θ13 to be clearly non-zero These disappearance experiments are sensitive to the oscillation amplitude and have measured sin2(2θ13) to be ∼ 0.1. All published results are based on background models, which are derived from data taken during reactor-on periods using certain assumptions about the origin of correlated background events. This procedure contributes, along with detection efficiency and reactor source errors, to the total systematic uncertainty. We will show that our background rate determination is in full agreement with
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