Kaon production in heavy ion reactions at intermediate energies

Abstract

The article reviews the physics related to kaon and antikaon production in heavy ion reactions at intermediate energies. Chiral dynamics predicts substantial modifications of the kaon properties in a dense nuclear environment. The status of the theoretical predictions as well as experimental evidences for medium effects such as repulsive/attractive mass shifts for K + /K − are reviewed. In the vicinity of the thresholds, and even more pronounced below threshold, the production of strangeness is a highly collective process. Starting from elementary reaction channels the phenomenology of K + and K − production, i.e. freeze-out densities, time scales etc. as derived from experiment and theoretical transport calculations is presented. Below threshold kaon production shows a high sensitivity on the nuclear compression reached in heavy ion reactions. This allows to put constraints on the nuclear equation-of-state which are finally discussed.

Constraints on the equation of state of cold dense matter from nuclear physics and astrophysics

“…Pressure versus baryon number density (in units of the saturation density n 0 ) for symmetric nuclear matter for the EDFs BSk19, BSk20, and BSk21 [2][3][4]. Shaded areas correspond to the constraints obtained from nuclear flow [14] and kaon production [15] in heavy-ion collision experiments.…”

“…In particular, constraints on the EoS of symmetric nuclear matter have been obtained from the analysis of nucleon flow data [14] and kaon production [15]. These constraints are represented in Fig.…”

“…However, we emphasise that the constraints of Refs. [14,15] were not directly inferred from experimental data, but were rather determined using specific transport models. Therefore, the uncertainties may have been underestimated.…”

Correlation of the neutron star crust-core properties with the slope of the symmetry energy and the lead skin thickness

“…The properties of asymmetric nuclear systems have also been studied in terrestrial laboratories in past years [2,3], but many aspects still rely on theoretical models. Constraints on the behavior of the symmetry energy above nuclear saturation density have been coming from experiments with new neutron-rich radioactive beams, and in relativistic heavy-ion collisions, giant monopole resonances [4], isobaric analog states [5], or meson production (pions [6] and kaons [7]) in heavy-ion collisions.…”

On the strangeness -1 S-wave meson-baryon scattering

“…Apart from that, these interactions are interrelated with many other interesting areas, as listed in ref. [21], e.g., possible kaon condensation in neutron-proton stars [26,27,28,29], large yields of K − in heavy ions collisions [30,31], kaonic atoms [32] or non-zero strangeness content of the proton [33,34].…”