Fig. 5. Confidence regions of the neutrino oscillation parameter space that can be potentially detected by PLANCK surveyor by using CMB anisotropy measurements. Panel a : the allowed confidence regions at CL (A) and at CL (B) obtained for (continuous lines) and (dashed lines). The target model has eV² and (see also the text). Panel b : the allowed confidence regions at CL (A) and at CL (B) for . The target model has: eV² and (continuous lines) and eV² and (dashed lines). In each panel we also present (dash-dotted lines) the allowed regions of and at 99 CL (A1) and 90 CL (B1) measured by the MACRO experiment.