Nuclear fragmentation induced by low-energy antiprotons within a microscopic transport approach

Within the framework of the Lanzhou quantum molecular-dynamics transport model, the nuclear fragmentation induced by low-energy antiprotons has been investigated thoroughly. A coalescence approach is developed for constructing the primary fragments in phase space. The secondary decay process of the fragments is described by a well-known statistical code. It is found that the localized energy released in antibaryon-baryon annihilation is deposited in a nucleus mainly via pion-nucleon collisions, which leads to the emissions of pre-equilibrium particles, fission, evaporation of nucleons, light fragments, etc. The strangeness exchange reactions dominate the hyperon production. The averaged mass loss increases with the mass number of target nucleus. A bump structure in the domain of intermediate mass for heavy targets appears owing to the contribution of fission fragments.

Figure 1

Total multiplicities of pseudoscalar meson (a) pions, (b) etas, (c) kaons, and (d) antikaons as a function of mass number of target nuclei in antiproton induced reactions.

Figure 2

The same as in Fig. 1, but for the (a) $\mathrm{\Lambda }$ and (b) $\mathrm{\Sigma }$ production.

Figure 3

Rapidity distributions of light complex particles (nucleons, hydrogen, and helium isotopes) in antiproton induced reactions on the nuclei of (a) ${}^{20}\mathrm{Ne}, {}^{40}\mathrm{Ca}, {}^{95}\mathrm{Mo}, {}^{138}\mathrm{Ba}, {}^{197}\mathrm{Au}$ and (b) ${}^{63}\mathrm{Cu}, {}^{124}\mathrm{Sn}, {}^{165}\mathrm{Ho}, {}^{181}\mathrm{Ta}, {}^{238}\mathrm{U}$ at the momentum of 200 MeV/c.

Figure 4

The same as in Fig. 3, but for the kinetic-energy spectra.

Figure 5

(a) Mass spectra and (b) charge distributions of fragments produced in the $\overline{p}+{}^{197}\mathrm{Au}$ reaction at an incident momentum of 200 MeV/c combined with the statistical decay code gemini. The mass yields from the LEAR facility at CERN [27] are shown for comparison.

Figure 6

Fragment distributions in antiproton induced reactions at the incident momentum of 200 MeV/c as functions of (a) mass number on ${}^{12}\mathrm{C}$, (b) mass number on ${}^{20}\mathrm{Ne}$, (c) charged number on ${}^{12}\mathrm{C}$, and (d) charged number on ${}^{20}\mathrm{Ne}$, respectively.

Figure 7

The same as in Fig. 6, but for (a) mass number on ${}^{40}\mathrm{Ca}$, (b) mass number on ${}^{63}\mathrm{Cu}$, (c) charged number on ${}^{40}\mathrm{Ca}$, and (d) charged number on ${}^{63}\mathrm{Cu}$, respectively.

Figure 8

Fragmentation reactions induced by antiprotons and compared with the LEAR data [28] for the fragment (a) mass on ${}^{95}\mathrm{Mo}$, (b) mass on ${}^{165}\mathrm{Ho}$, (c) charged number ${}^{95}\mathrm{Mo}$, and (d) charged number distributions on ${}^{165}\mathrm{Ho}$, respectively.

Figure 9

Fragment distributions in the antiproton induced reactions for the spectra of mass (a) ${}^{124}\mathrm{Sn}$ and (b) ${}^{138}\mathrm{Ba}$ and charge number (c) ${}^{124}\mathrm{Sn}$ and (d) ${}^{138}\mathrm{Ba}$, respectively.

Figure 10

The same as in Fig. 9, but for the mass distributions on (a) ${}^{181}\mathrm{Ta}$ and (b) ${}^{238}\mathrm{U}$ as well as charge spectra on (c) ${}^{181}\mathrm{Ta}$ and (d) ${}^{238}\mathrm{U}$, respectively.

Figure 11

Averaged mass removal as a function of mass number of target nuclei [27].

Figure 12

Correlation of the intermediate mass fragments (IMFs) and charged particle multiplicity produced in $\overline{p}$ induced reactions on different targets.