sensitivity to $d_i$. Taking $a_0 \sim m_R$, figs. (\[Fph\_A\]) show that values around $0.02$ for $| {\cal I}m (a_{i}) |/m_R$ would require an experimental sensitivity to $d_e$ and $d_\mu$ respectively at the level of $10^{-28}-10^{-29}$ e cm and $2~10^{-26}-2~10^{-27}$ e cm, the exact value depending on the particular point of the $(\ti M_1, m_R)$ plane. However, to avoid charge and color breaking, the constraint $a_0/m_R \le 3$ in general applies. Thus, focusing for instance around $m_R \approx 500$ GeV, the FC contribution cannot exceed $\sim10^{-28}$ e cm for $d_e$ and $\sim 2~ 10^{-26}$ e cm for $d_\mu$, even with highly hierarchical right-handed neutrinos. Notice that the former value could be at hand of future experimental searches for $d_e$, while the latter is at the very limit of the planned experimental sensitivity to $d_\mu$. Allowing for smaller $m_R$ values, $m_R \approx 200$ GeV, the FC seesaw upper estimate comes close to the present limit for $d_e$ while it cannot be more than $\sim 2~10^{-25}$ e cm for $d_\mu$.

The result for $d_\mu$ is thus a kind of “negative” one, since its eventual future discovery above $\sim 2~10^{-25}$ e cm couldn’t be attributed to the radiative FC contribution of the seesaw. Even 