Nuclear in-medium effects of strange particles in proton-nucleus collisions

The dynamics of strange particles produced in proton-induced nuclear reactions near threshold energies has been investigated within the Lanzhou quantum molecular dynamics transport model. The in-medium modifications on particle production in dense nuclear matter are considered through corrections on the elementary cross sections via the effective mass and the mean-field potentials. It is found that the attractive antikaon-nucleon potential enhances the subthreshold $\overline{K}$ production and influences the structure of inclusive spectra. The strangeness production is strongly suppressed in proton-induced reactions in comparison to heavy-ion collisions. The kaon-nucleon and antikaon-nucleon potentials change the structures of rapidity and transverse momentum distributions and the inclusive spectra. The measured $K^{-}/K^{+}$ ratios in collisions of ${}^{12}\mathrm{C}+{}^{12}\mathrm{C},{}^{197}\mathrm{Au}+{}^{197}\mathrm{Au},p+{}^{12}\mathrm{C}$, and $p+{}^{197}\mathrm{Au}$ from the KaoS Collaboration have been well explained with the inclusion of the in-medium potentials.

Figure 1

Multiplicities of $\pi ,\Lambda ,K^{+}$, and $K^{-}$ per participating nucleon in the reactions of ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}$ and $p+{}^{12}\mathrm{C}$ as a function of the available energy, i.e., the $Q$ value is the difference of invariant energy to the threshold value $Q=\sqrt{s}-\sqrt{s_{th}}$.

Figure 2

Rapidity distributions of strange particles produced in collisions of protons on ${}^{12}\mathrm{C}$ and ${}^{197}\mathrm{Au}$.

Figure 3

The same as in Fig. 2 but for the transverse mass spectra.

Figure 4

The inclusive spectra of strange particles ($K^{+},\Lambda$, and $K^{-}$) produced in the proton-induced reactions on ${}^{12}\mathrm{C}$ and ${}^{197}\mathrm{Au}$ with and without inclusions of the in-medium potentials at incident momenta of 3.5 and 5 GeV/c, respectively.

Figure 5

The ratio of $K^{-}/K^{+}$ as a function of transverse mass (kinetic energy) in collisions of ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}$ and protons on ${}^{12}\mathrm{C}$ and ${}^{197}\mathrm{Au}$ at the beam energies of $1.8A\mathrm{GeV}$ and 2.5 GeV, respectively. Reactions of ${}^{197}\mathrm{Au}+{}^{197}\mathrm{Au}$ at the incident energy of $1.5A\mathrm{GeV}$.