In-medium effect and collective flow of pion production in intermediate energy heavy-ion collisions

Abstract

<p indent="0mm">The production mechanism of pion in intermediate energy heavy-ion collisions has been studied by LQMD (Lanzhou Quantum Molecular Dynamics) model. The time evolution of multiplicity, rapidity distribution, transverse momentum spectra, collective flows, etc., is calculated in collisions of ⁴⁰Ca+⁴⁰Ca, ⁹⁰Zr+⁹⁰Zr, ⁹⁶Zr+⁹⁶Zr, ⁹⁶Ru+⁹⁶Ru and ¹⁹⁷Au+¹⁹⁷Au. The Δ-nucleon interaction potential and scattering, π-nucleon potential and scattering and stiffness of symmetry energy are to be investigated systematically. It is found that the π⁻/π⁺ ratio is influenced by the isospin-dependent Δ-nucleon potential and the pion production is suppressed by the in-medium Δ-nucleon scattering, in particular in the region of mid-rapidity and low-momentum of pion production. The transverse momentum spectra, rapidity distribution, collective flows and π⁻/π⁺ ratio are influenced by the isospin-dependent π-nucleon potential, in particular in the mid-rapidity and high-momentum region. The antiflow of π⁺ production is caused by the shadowing effect of participant nucleons. The triangular flow (<italic>V</italic>₃) is similar to the directed flow (<italic>V</italic>₁), but the magnitude of quadrangular flow (<italic>V</italic>₄) is very small for the pion production.</p>

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