Fig. 3.

Distribution of the $\Delta t$ between couples of parent–daughter events in the ${}^{238}$U (${}^{222}$Rn–${}^{218}$Po, left) and ${}^{232}$Th (${}^{224}$Ra–${}^{220}$Rn, right) decay chains. The fit function (solid line) is composed by an exponential plus a flat background (dashed line at zero counts) to account for possible random delayed coincidences, whose integral (${\text{N}}_{\text{BKG}}$) eventually results to be compatible with zero in both cases. The half-life parameter reconstructed by the fit is compatible in both cases with the values reported in literature, thus confirming the effectiveness and the reliability in the identification of delayed coincidences