Antistrange meson-baryon interaction in hot and dense nuclear matter

Abstract

We present a study of in-medium cross sections and (off-shell) transition rates for the most relevant binary reactions for strange pseudoscalar meson production close to threshold in heavy-ion collisions at FAIR energies. Our results rely on a chiral unitary approach in coupled channels which incorporates the s-and p-waves of the kaonnucleon interaction. The formalism, which is modified in the hot and dense medium to account for Pauli blocking effects, mean-field binding on baryons, and pion and kaon self-energies, has been improved to implement unitarization and self-consistency for both the s-and p-wave interactions at finite temperature and density. This gives access to in-medium amplitudes in several elastic and inelastic coupled channels with strangeness content S = −1. The obtained total cross sections mostly reflect the fate of the Λ(1405) resonance, which melts in the nuclear environment, whereas the off-shell transition probabilities are also sensitive to the in-medium properties of the hyperons excited in the p-wave amplitudes [Λ, Σ and Σ * (1385)]. The single-particle potentials of these hyperons at finite momentum, density and temperature are also discussed in connection with the pertinent scattering amplitudes. Our results are the basis for future implementations in microscopic transport approaches accounting for off-shell dynamics of strangeness production in nucleus-nucleus collisions.

Why hadronic resonances and particle unstable states are interesting?

“…At the moment all the theoretical models use measured free cross sections or parameterizations if measured cross sections are not available. Recently it has been shown that at finite temperature cross sections will be modified [11]. To take this into account provides a new task for the transport approaches.…”

S= −1 meson-baryon interaction in hot and dense nuclear matter: chiral symmetry, many-body and unitarization for a road to GSI/FAIR

“…Such kind of approaches successfully describe theK meson interactions in nuclear matter, accounting for a shallow attractiveK potential at nuclear matter density (40-60 MeV) and a broad spectral function. Our present results improve on this model by implementing the unitarization of scattering amplitudes in both the s and p waves of theKN interaction, at finite density and temperature, within the imaginary time (Matsubara) formalism [12]. The scattering amplitudes are modified in the medium from Pauli-blocking on intermediate nucleon states, Bose enhancement of light mesons, mean-field baryonic binding potentials and the self-energy of mesons (particularly, pions and kaons in, e.g.KN, πY).…”

“…Σ * → ΛNN −1 , ΣNN −1 ) related with the selfenergy of pions and kaons (the Σ * evolution is better appreciated in the right panel of the scattering amplitudes permits to obtain momentum-dependent nuclear optical potentials for these hyperons at different temperatures and densities (cf. [12] for full details).…”

K* dynamics in heavy ion collisions

“…For theK * in a dense nuclear medium the major effects come both from theKπ decay channel, where theK is largely modified [3][4][5], and from the highly inelasticK * N interaction [1], leading to decay widths as large as 200 MeV at normal matter density ρ 0 . The K * interaction with the medium is much more moderate.…”

“…They can either scatter elastically or be reabsorbed. Furthermore the K/K and the π are also modified by the medium [3][4][5][6], which further distorts the signal from the initial decay reaction.…”