SNO and the solar neutrino problem

Abstract

We study the implication of the first neutral current (NC) data from SNO. We perform model independent and model dependent analyses of the solar neutrino data. The inclusion of the first SNO NC data in the model independent analysis determines the allowed ranges of $^{8}{B}$ flux normalization and the $\nu_e$ survival probability more precisely than what was possible from the SK and SNO CC combination. Transitions to pure sterile states are seen to be hugely disfavored however transition to ``mixed'' states are still viable with a probability of finding about 30% sterile component in the resultant beam at $1\sigma$. We perform global $\nu_e-\nu_{active}$ oscillation analyses of solar neutrino data including the recent SNO results. LMA emerges as a huge favorite while LOW appears at the $3\sigma$ level. All the other solutions are disfavored at $3\sigma$ while SMA is virtually ruled out. Maximal mixing is disfavored at $3\sigma$. We explore in some details the reasons for the incompatibility of the maximal mixing solution and the LOW solution with the global solar neutrino data.