Proposal to observe the strong Van der Waals force in the low energy neutron-Pb scattering

Abstract

In the neutron-Pb scattering in the MeV. region, existence of the long range interaction has been known and people have hopefully expected to understand it as the effect of the electric polarization of the neutron. However the precise determination of $α_{n}$ in the very low energy region indicates that the polarizability of the neutron $α_{n}$ is around two order of magnitude smaller compared to what is expected in the phenomena in the MeV. region. We need another strong long range potential which decreases faster than $r^{-4}$. On the other hand, analysis of the low energy proton-proton data revealed the existence of the strong long range potential whose tail was $V(r) \sim -C/r^α$ with $α=6.08$. The neuton-nucleus scattering is a good place to see such a force, since the strength $C$ is magnified by factor $A$, the mass number. Using the long range parameters obtained in p-p, we predict the characteristic angular dependency of the n-Pb amplitude for fixed energy. Appearance of a cusp at $ν=0$, which points upward, in the once subtracted P-wave amplitude $a_{1}(ν)/ν$ is predicted.