Coulomb Suppression Effects in the Proton-Proton Elastic Scattering Extracted from the²H(p,pp)nReaction

Abstract

The Trojan Horse Method (THM) 1)-12) is an indirect method that allows twobody cross section measurements at energy far below the Coulomb barrier, starting from a three-body reaction.It is possible to extract a two-body cross section (a + b → c + C) from a measured three-body one (a + A → c + C + x) where the chosen nucleus A has a high probability to be clusterized into x⊕b and x behaves as a spectator to the process (quasi-free mechanism). If the reaction energy is higher than the Coulomb barrier in the entrance channel of the three-body reaction, the two-body interaction can be considered as taking place inside the nuclear field. Therefore, in this picture, the extracted two-body cross section refers to the nuclear interaction only, the Coulomb barrier being already overcome in the entrance channel. 4)The present paper reports on the application of this method to the p-p scattering, the simplest case where the Coulomb suppression can be observed. The p-p cross section is well-known. Its energy trend is observed to be very similar to that of n-n or p-n systems (≈ 1/v) except at low proton energies where a deep minimum shows up (E lab = 382.43 keV, θ cm = 90 • ) due to the interference between the nuclear and the Coulomb scattering amplitudes. 13) So, if one extracts the p-p cross section, under the THM assumptions from a suitable three-body one, like the 2 H(p, pp)n reaction, this extracted cross section is expected to show Coulomb suppression effects. For this reason, the 2 H(p, pp)n reaction was studied at Laboratori Nazionali del Sud (LNS), INFN, Catania, at proton energy higher than the p+d Coulomb barrier and such that the p-p relative energy in the exit channel is in the region of the deep minimum.