Antiproton reflection by a solid surface

In this article, the first experimental evidence is presented for the reflection of a conspicuous fraction (∼ 30%) of a beam of low energy antiprotons by an aluminum wall. This rare evidence comes from the new analysis of a set of annihilations of antiprotons stopped in rarefied helium gas after hitting the end wall of the apparatus. These results, supported by Monte Carlo simulations, show that the interaction between the antiprotons at low energies (\(\lesssim 10\) keV) and the solid surface is dominated by Rutherford-type scattering on aluminum nuclei, and contradict the common belief according to which the interactions between matter and antimatter are dominated by the reciprocally destructive phenomenon of annihilation.