https://doi.org/10.1140/epja/i2014-14037-6
Review
Probing nuclear symmetry energy at high densities using pion, kaon, eta and photon productions in heavy-ion collisions
1
Department of Physics, Tsinghua University, 100084, Beijing, China
2
Collaborative Innovation Center of Quantum Matter, Beijing, China
3
Institute of Modern Physics, Chinese Academy of Sciences, 730000, Lanzhou, China
4
Department of Physics and Astronomy, Shanghai Jiao Tong University, 200240, Shanghai, China
5
Department of Physics and Astronomy, Texas A&M University-Commerce, 75429-3011, Texas, USA
6
National Institute of Metrology, 100013, Beijing, China
7
Institute of Particle Physics, Central China Normal University, 430079, Wuhan, China
* e-mail: xiaozg@tsinghua.edu.cn
Received:
30
July
2013
Revised:
22
September
2013
Accepted:
27
September
2013
Published online:
26
February
2014
The high-density behavior of nuclear symmetry energy is among the most uncertain properties of dense neutron-rich matter. Its accurate determination has significant ramifications in understanding not only the reaction dynamics of heavy-ion reactions, especially those induced by radioactive beams, but also many interesting phenomena in astrophysics, such as the explosion mechanism of supernova and the properties of neutron stars. The heavy-ion physics community has devoted much effort during the last few years to constrain the high-density symmetry using various probes. In particular, the /
ratio has been most extensively studied both theoretically and experimentally. All models have consistently predicted qualitatively that the
/
ratio is a sensitive probe of the high-density symmetry energy especially with beam energies near the pion production threshold. However, the predicted values of the
/
ratio are still quite model dependent mostly because of the complexity of modeling pion production and reabsorption dynamics in heavy-ion collisions, leading to currently still controversial conclusions regarding the high-density behavior of nuclear symmetry energy from comparing various model calculations with available experimental data. As more
/
data become available and a deeper understanding about the pion dynamics in heavy-ion reactions is obtained, more penetrating probes, such as the K
+/K
0 ratio,
meson and high-energy photons are also being investigated or planned at several facilities. Here, we review some of our recent contributions to the community effort of constraining the high-density behavior of nuclear symmetry energy in heavy-ion collisions. In addition, the status of some worldwide experiments for studying the high-density symmetry energy, including the HIRFL-CSR external target experiment (CEE) are briefly introduced.
© SIF, Springer-Verlag Berlin Heidelberg, 2014