Power-Spectrum Analyses of Super-Kamiokande Solar Neutrino Data: Variability and its Implications for Solar Physics and Neutrino Physics

摘要

There have been conflicting claims as to whether or not power-spectrumanalysis of the Super-Kamiokande solar neutrino data yields evidence ofvariability. Comparison of these claims is complicated by the fact that therelevant articles may use different datasets, different methods of analysis,and different procedures for significance estimation. The purpose of thisarticle is to clarify the role of power spectrum analysis. To this end, weanalyze only the Super-Kamiokande 5-day dataset, and we use a standardprocedure for significance estimation proposed by the Super-Kamiokandecollaboration. We then analyze this dataset, with this method of significanceestimation, using six methods of power spectrum analysis. We find that thesignificance of the principal peak in the power spectrum (that at 9.43 yr-1witha depth of modulation of 7%) shows a clear correlation with the amount andrelevance of the information being processed, as would be expected if therewere a real signal in the data. The significance level reaches 99.3% for onemethod of analysis. We discuss, in terms of sub-dominant processes, possibleneutrino-physics interpretations of the apparent variability of theSuper-Kamiokande measurements, and we suggest steps that could be taken toresolve the question of variability of the solar neutrino flux.