Strange particle production and hypernucleus formation in medium and high energy heavy-ion collisions

Abstract

The nuclear matter at supra-saturation densities might be created in medium and high energy heavy-ion collisions. The strangeness ingredient in dense nuclear matter impacts the equation of state and maybe exists in the neutron stars. On the other hand, heavy-ion collisions provide a unique way for producing the neutron-rich hypernuclides. In this article, the new progress on strangeness physics in heavy-ion collisions is reviewed. Possible experiments at the high-intensity heavy-ion accelerator facility (HIAF) are to be discussed, in particular on the topics of the high-density nuclear equation of state and hypernuclide in the neutron-rich domain. Within the framework of the Lanzhou quantum molecular dynamics (LQMD) model, the strangeness production and high-density nuclear equation of state in heavy-ion collisions near threshold energies has been investigated, i.e., for the reactions of $^{58}$Ni+$^{58}$Ni and $^{197}$Au+$^{197}$Au. The formation mechanism of $\Lambda$-hyperfragments in heavy-ion collisions is to be investigated. A coalescence approach is developed for constructing the primary fragments in phase space. The secondary decay process of the fragments is described by the well-known statistical code. The impacts of nuclear equation of state on the hyperfragment formation are discussed. The mass, charge and kinetic energy spectra of hypernuclides produced in heavy-ion collisions are thoroughly analyzed. It is found that the kaon yields in the high kinetic energy domain are useful for extracting the high-density nuclear equation of state. The $K^{+}$ yields are strongly suppressed with a hard equation of state. However, the hyperon production is weakly influenced by the incompressibility of nuclear matter. The $\Lambda$-nucleon potential impacts the hypernuclide formation, i.e., the attractive potential enhancing the hypernuclide yields. The heavy-ion collisions are available to produce the light mass neutron-rich hypernuclides and the mid-central collisions are favorable for the medium mass hypernuclide formation. Free hyperons are captured by nucleonic fragments to form hypernuclides in the domain of lower kinetic energies and narrower rapidities. A soft equation of state is available for producing the hyperfragments. The results are very valuable for the forthcoming hypernuclide physics at HIAF.