Determination of the density region of the symmetry energy probed by the ${\pi }^{-}/{\pi }^{+}$ ratio

Abstract

The nuclear symmetry energy around or below saturation density has been extensively studied and roughly pinned down, while its behavior at suprasaturation densities is rather uncertain. Related experimental studies are being carried out or planned at facilities that offer radioactive beams worldwide. Towards the physical goal of probing the nuclear symmetry energy at high densities, π measurements in the medium nuclei 132Sn + 124Sn collisions at 300 or 200 MeV/nucleon incident beam energies are ongoing at the Radioactive Isotope Beam Facility at RIKEN in Japan. However, our studies show that the observable π−/π+ ratio in the 132Sn + 124Sn reactions at 300 or 200 MeV/nucleon incident beam energies mainly probes the symmetry energy around the saturation density. Only the π−/π+ ratio in the heavy reaction system and at relatively high incident beam energies may mainly probe the symmetry energy at suprasaturation densities.

Effects of curvature of the symmetry energy in Sn+Sn reactions at 270 MeV/nucleon

“…8, one can see that the double π − /π + ratio is somewhat more sensitive to the low-density symmetry energy, which is consistent with that shown in Ref. [21]. However, one can deduce the high-density behavior of the symmetry energy once the K sym is probed and constrained from RIBF/RIKEN experiments.…”

“…In this study, we show how to get information of the K sym from the ongoing RIBF/RIKEN related data. Although the isotope Sn+Sn reaction at 270 MeV/nucleon at RIBF/RIKEN in Japan cannot effectively probe the high-density symmetry energy [21], the extraction of the curvature of the symmetry energy through interpretation of related data can give implication on the high-density behavior of the symmetry energy Since the slope L of the symmetry energy at saturation density has been constrained with high probability [5].…”

Quiescent luminosities of transiently accreting neutron stars with neutrino heating due to charged pion decay

“…where N π + , N π − are the total numbers of π + , π − produced per accreted nucleon, respectively. As the experiment data of charged pion production from the interaction of nucleus-nucleus collisions still remains incomplete, we can estimate N π + and N π − from the isospindependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport simulations [31][32][33][34].…”

Initialization effects of nucleon profile on the $π$ yields in heavy-ion collisions at medium energies

“…Recent experimental data consist of the 197 Au + 197 Au reaction at 400 MeV/nucleon for incident energy within the ASY-EOS experiment at the GSI laboratory [6], and of the 132 Sn + 132 Sn reaction at a beam energy of 0.3 GeV/nucleon, carried out at RIKEN in Japan [7]. They could provide information about the equation of state (EOS) [8][9][10][11], short-range correlations (SRC) [12] and medium effects in scattering cross sections [13,14]. Both theoretical and experimental studies have pointed out that the π meson is one of the promising probes to study the nuclear structure and reaction aspects of heavy ion collisions [9,10,14,15].…”