Constraining neutrino oscillation parameters with current solar and atmospheric data

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  • 18 July 2002
Abstract
We analyse the impact of recent solar and atmospheric data in the determination of the neutrino oscillation parameters, taking into account that both the solar nu_e and the atmospheric nu_mu may convert to a mixture of active and sterile neutrinos. In addition to the recent SNO neutral current (NC), spectral and day/night data we add the latest 1496-day solar and 1489-day atmospheric Super-K neutrino data samples. By investigating in detail the impact of the recent SNO NC, spectral and day/night data, we confirm the clear preference of the LMA solution of the solar neutrino problem and obtain that the LOW, VAC, SMA solutions are disfavoured with a Delta_chi^2 = 9, 9, 23, respectively. Furthermore, we find that the global solar data constrains the admixture of a sterile neutrino to be less than 45% at 99% CL. A pure sterile solution is ruled out with respect to the active one at 99.996% CL. By performing an improved fit of the atmospheric data, we also update the corresponding regions of oscillation parameters. We find that the recent atmospheric Super-K (1489-day) and MACRO data have a strong impact on constraining a sterile component in atmospheric oscillations: if the nu_mu is restricted to the atmospheric mass states only a sterile admixture of 16% is allowed at 99% CL, while a bound of 35% is obtained in the unconstrained case. Pure sterile oscillations are disfavoured with a Delta_chi^2 = 34.6 compared to the pure active case.

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