Solar neutrino event spectra: Tuning SNO to equalize Super-Kamiokande - art. no. 113016

The Super-Kamiokande (SK) and the Sudbury Neutrino Observatory (SNO) experi ments are monitoring the flux of B-8 solar neutrinos through the elect;on e nergy spectrum from the reactions nu (e,mu,tau)+ e(-)--> nu (e,mu,tau)+e(-) and nu (e)+d-->p+p+e(-), respectively. We show that the SK detector respon se to B-8 neutrinos in each bin of the electron energy spectrum (above 8 Me V) can be approximated, with good accuracy, by the SNO detector response in an appropriate electron energy range (above 5.1 MeV). For instance, the SK response in the bin [10, 10.5] MeV is reproduced ("equalized") within simi lar to2% by the SNO response in the range [7.1, 11.75] MeV. As a consequenc e, in the presence of active neutrino oscillations, the SK and SNO event ra tes in the corresponding energy ranges turn out to be linearly related, for any functional form of the oscillation probability. Such equalization is n ot spoiled by the possible contribution of hep neutrinos (within current ph enomenological limits). In perspective, when the SK and the SNO spectra wil l both be measured with high accuracy, the SK-SNO equalization can be used to determine the absolute B-8 neutrino flux, and to cross-check the (non)ob servation of spectral deviations in SK and SNO. At present, as an exercise, we use the equalization to "predict" the SNO energy spectrum, on the basis of the current SK data. Finally, we briefly discuss some modifications or limitations of our results in the case of sterile nu oscillations and of re latively large Earth matter effects.