Suppression of the Coulomb Interaction in the Off-Energy-Shell $p-p$ Scattering from the $p+d\to p+p+n$ Reaction

Off-energy-shell effects in $p-p$ scattering have been investigated at $p-p$ relative energies from 600 down to 80 keV applying the Trojan horse method (THM) to the $p+d\to p+p+n$ reaction at 5 MeV. In contrast with the on-energy-shell case, no Coulomb-nuclear interference minimum has been found in the extracted THM $p-p$ cross section, due to the suppression of the Coulomb amplitude as predicted by the half-off-energy shell calculations. This hypothesis is strengthened by the agreement between THM $p-p$ data and calculated on-energy-shell $n+n$, $n+p$ and nuclear $p+p$ cross sections.

Figure 1

Experimental neutron momentum distribution. The dashed line represents the shape given by the square of the $n-p$ Hulthén bound state wave function in momentum space.

Figure 2

Pole diagram describing the PWIA mechanism.

Figure 3

THM two-body cross section (black dots from present experimental work, red triangles, and blue stars from previous work [7]) vs $E_{pp}$. Solid line represents the theoretical OES $p-p$ cross section calculated as explained in the text. The dashed-dotted line is the HOES cross section calculated using Eq. (3).

Figure 4

THM two-body cross section (black dots from present experimental work, red triangles, and blue stars from previous work [7]) vs $p-p$ relative energy $E$, compared with the on-shell $n-n$ (solid line), $p-n$ (dashed line), and pure nuclear $p-p$ (dotted line) ones. The HOES calculated cross section is also reported as the dashed-dotted line.