Neutrinoless Double Beta Decay: 2015 Review

Figure 22

Representation of in the unitarity triangle. The internal point in the middle of the small colored bar is identified by the constraints from the oscillation parameters. The colored regions correspond to (red), (orange), and (yellow). The distance from a side represents the size of the corresponding mixing element . The inner shaded regions of the triangle enclose the areas where for a lightest neutrino mass that can vary from  eV to the value which corresponds to a cosmological mass  eV (orange, 90% CL current bound) and  eV (gray, for purpose of illustration).