In this work a detailed spectral analysis for periodicity search of the time
series of the 8B solar neutrino flux released by the SNO Collaboration is
presented. The data have been publicly released with truncation of the event
times to the unit of day (1 day binning); they are thus suited to undergo the
traditional Lomb-Scargle analysis for periodicity investigation, as well as an
extension of such a method based on a likelihood approach. The results of the
analysis presented here confirm the absence of modulation signatures in the SNO
data. For completeness, a more refined "1 day binned" likelihood is also
illustrated, which approximates the unbinned likelihood methodology, based upon
the availability of the full time information, adopted by the SNO
collaboration. Finally, this work is completed with two different joint
analyses of the SNO and Super-Kamiokande data, respectively, over the common
and the entire data taking periods. While both analyses reinforce the case of
the constancy of the neutrino flux, the latter in addition provides evidence of
the detection at the 99.7% confidence level of the annual modulation spectral
line due to the Earth's orbit eccentricity around the SunComment: 27 pages, 29 figures. Joint periodicity analysis of the SNO and
Super-Kamiokande data added. Accepted for publication on Phys. Rev.
