Nuclear annihilation by antinucleons

We examine the momentum dependence of $\overline{p}p$ and $\overline{n}p$ annihilation cross sections by considering the transmission through a nuclear potential and the $\overline{p}p$ Coulomb interaction. Compared to the $\overline{n}p$ annihilation cross section, the $\overline{p}p$ annihilation cross section is significantly enhanced by the Coulomb interaction for projectile momenta below $p_{\mathrm{lab}}<500$ MeV/$c$, and the two annihilation cross sections approach the Pomeranchuk's equality limit [JETP Lett. 30, 423 (1956)] at $p_{\mathrm{lab}}\sim 500$ MeV/$c$. Using these elementary cross sections as the basic input data, the extended Glauber model is employed to evaluate the annihilation cross sections for $\overline{n}$ and $\overline{p}$ interaction with nuclei and the results compare well with experimental data.

Figure 1

(a) Antiproton-proton annihilation cross sections as a function of the antiproton momentum in the laboratory frame. The solid curve represents the $\overline{p}p$ annihilation cross section of Eq. (1). The experimental data points are from the compilation of [25], where the individual experimental sources can be found. (b) Contributions from different partial waves to the total annihilation cross sections.

Figure 2

(a) Antineutron-proton annihilation cross sections as a function of the antineutron momentum in the laboratory frame. Solid curve: $\overline{n}p$ annihilation cross section using Eq. (1) with the Gamow factor equal to 1. Solid triangle: experimental data from the OBELIX Collaboration [17] and open circle denotes experimental data from BNL [18]. (b) Contributions from different partial waves to the total annihilation cross sections.

Figure 3

Comparison of $\overline{p}p$ and $\overline{n}p$ annihilation cross sections as a function of the antiproton momentum in the laboratory frame.

Figure 4

$\overline{p}A$ annihilation cross sections as a function of the antiproton momentum in the laboratory frame. The experimental data are from Ref. [25]. The basic $\overline{p}p$ curve is calculated from Eq. (1) and the rest are from the extended Glauber model.

Figure 5

$\overline{n}\mathrm{Fe}$ annihilation cross section as a function of the antineutron momentum in the laboratory frame. Comparing the result from Eq. (1) with several sets of experimental data.

Figure 6

$\overline{n}A$ annihilation cross section as a function of the antineutron momentum in the laboratory frame. Comparing the result from Eq. (1) with experimental data from [24].