Detectability matrices of massive neutrinos. Each matrix element shows the scale s_cross (Eq. 14) below which, considering all triangles with a scale larger than s_cross, we obtained a significant detection of the signal from massive neutrinos in the connected 3PCF. The matrices in the upper and lower rows show the values for a 1σ and 3σ statistical significance (Eq. 13), respectively, computed for a volume of 10 h⁻³ Gpc³. In each matrix, M_ν increases from left to right, and redshifts increase from bottom to top. We show the results for the three configurations corresponding to the lines in Fig. 1, i.e., from left to right: triangles with s₁₂ = 10 h⁻¹ Mpc, isosceles triangles (η = 0), and quasi-isosceles triangles with η = 4. The quantity s_cross represents one of the two sides, s₁₂ or s₁₃, depending on the configuration: in particular, in Eq. (14) we set s = s₁₃ for triangles with fixed s₁₂, and s = s₁₂ for isosceles and η = 4 triangles. Brighter colors represent better detection levels, i.e., occurring at larger scales. The label ND stands for “not detectable” above the specified significance threshold at any scale. A lower limit is indicated whenever the signal is detectable above a given threshold of statistical significance over the entire range of scales considered in our analysis.