12 Nuclear Matter Properties at High Densities…
159
or will become available, which allow further studies of the symmetry energy by
different experimental methods. But the highest energies and consequently highest
densities will be accessed with FAIR/Super-FRS facility. The super fragment separator Super-FRS will have a magnetic rigidity of 20 Tm and will provide radioactive
beams up to 1 GeV/nucleon. This will offer the possibility to study the symmetry
energy at high densities. Nevertheless, the neutron-proton asymmetry which may
be accessed in such experiments is not significantly larger than the one reached in
Au+Au or Pb+Pb collisions with the concomitant disadvantage that the collision
systems are getting smaller and the densities reached in the course of the reactions
are not as large as in the heavy Au-system. Hence, for flow and particle production
observables it may not be necessary to utilize radioactive beams, and stable beams
and targets would be sufficient. In such case, it would be impossible to generate double ratios in order to diminish systematic errors in the experiment and uncertainties
due to unknown input parameters to the models. This would require sophisticated
transport codes which have been benchmarked intensively to experimental data (see
[25] for an ongoing effort in comparing different transport codes).
Acknowledgements Results presented in this contribution have been obtained within the ASYEOS collaboration. See [22] for a complete list of authors.
References
1. B.A. Brown, Neutron radii in nuclei and the neutron equation of state. Phys. Rev. Lett. 85,
5296 (2000); X. Roca-Maza, M. Centelles, X. Viñas, M. Warda, Neutron skin of 208 Pb, nuclear
symmetry energy, and the parity radius experiment. Phys. Rev. Lett. 106, 252501 (2011)
2. B.-A. Li, L.-W. Chen, C.M. Ko, Recent progress and new challenges in isospin physics with
heavy-ion reactions. Phys. Rep. 464, 113–281 (2008)
3. B. Tsang et al., Constraints on the density dependence of the symmetry energy. Phys. Rev. Lett.
102, 122701 (2009)
4. A.W. Steiner et al., Isospin asymmetry in nuclei and neutron stars. Phys. Rep. 411, 325–375
(2005)
5. A. Bauswein et al. Identifying a first-order phase transition in neutron-star mergers through
gravitational waves. Phys. Rev. Lett. 122, 061102 (2019)
6. B.-A. Li, X. Han, Constraining the neutron-proton effective mass splitting using empirical
constraints on the density dependence of nuclear symmetry energy around normal density.
Phys. Lett. B 727, 276–281 (2013)
7. I. Tews et al., Symmetry parameter constraints from a lower bound on neutron-matter energy.
Astro. Phys. J. 848, 1 (2017)
8. P. Danielewicz et al., Symmetry energy III: Isovector skins. Nucl. Phys. A 958, 147–186 (2017)
9. J.M. Lattimer, A. Steiner, Constraints on the symmetry energy using the mass-radius relation
of neutron stars. Eur. Phys. J. A 50, 40 (2014)
10. B.A. Brown, Constraints on the Skyrme equations of state from properties of doubly magic
nuclei. Phys. Rev. Lett. 111, 232502 (2013)
11. Z. Xiao et al., Circumstantial evidence for a soft nuclear symmetry energy at suprasaturation
densities. Phys. Rev. Lett. 102, 062502 (2009)
12. W. Reisdorf et al., Systematics of pion emission in heavy ion collisions in the 1AGeV regime.
Nucl. Phys. A 781, 459–508 (2007)
159
or will become available, which allow further studies of the symmetry energy by
different experimental methods. But the highest energies and consequently highest
densities will be accessed with FAIR/Super-FRS facility. The super fragment separator Super-FRS will have a magnetic rigidity of 20 Tm and will provide radioactive
beams up to 1 GeV/nucleon. This will offer the possibility to study the symmetry
energy at high densities. Nevertheless, the neutron-proton asymmetry which may
be accessed in such experiments is not significantly larger than the one reached in
Au+Au or Pb+Pb collisions with the concomitant disadvantage that the collision
systems are getting smaller and the densities reached in the course of the reactions
are not as large as in the heavy Au-system. Hence, for flow and particle production
observables it may not be necessary to utilize radioactive beams, and stable beams
and targets would be sufficient. In such case, it would be impossible to generate double ratios in order to diminish systematic errors in the experiment and uncertainties
due to unknown input parameters to the models. This would require sophisticated
transport codes which have been benchmarked intensively to experimental data (see
[25] for an ongoing effort in comparing different transport codes).
Acknowledgements Results presented in this contribution have been obtained within the ASYEOS collaboration. See [22] for a complete list of authors.
References
1. B.A. Brown, Neutron radii in nuclei and the neutron equation of state. Phys. Rev. Lett. 85,
5296 (2000); X. Roca-Maza, M. Centelles, X. Viñas, M. Warda, Neutron skin of 208 Pb, nuclear
symmetry energy, and the parity radius experiment. Phys. Rev. Lett. 106, 252501 (2011)
2. B.-A. Li, L.-W. Chen, C.M. Ko, Recent progress and new challenges in isospin physics with
heavy-ion reactions. Phys. Rep. 464, 113–281 (2008)
3. B. Tsang et al., Constraints on the density dependence of the symmetry energy. Phys. Rev. Lett.
102, 122701 (2009)
4. A.W. Steiner et al., Isospin asymmetry in nuclei and neutron stars. Phys. Rep. 411, 325–375
(2005)
5. A. Bauswein et al. Identifying a first-order phase transition in neutron-star mergers through
gravitational waves. Phys. Rev. Lett. 122, 061102 (2019)
6. B.-A. Li, X. Han, Constraining the neutron-proton effective mass splitting using empirical
constraints on the density dependence of nuclear symmetry energy around normal density.
Phys. Lett. B 727, 276–281 (2013)
7. I. Tews et al., Symmetry parameter constraints from a lower bound on neutron-matter energy.
Astro. Phys. J. 848, 1 (2017)
8. P. Danielewicz et al., Symmetry energy III: Isovector skins. Nucl. Phys. A 958, 147–186 (2017)
9. J.M. Lattimer, A. Steiner, Constraints on the symmetry energy using the mass-radius relation
of neutron stars. Eur. Phys. J. A 50, 40 (2014)
10. B.A. Brown, Constraints on the Skyrme equations of state from properties of doubly magic
nuclei. Phys. Rev. Lett. 111, 232502 (2013)
11. Z. Xiao et al., Circumstantial evidence for a soft nuclear symmetry energy at suprasaturation
densities. Phys. Rev. Lett. 102, 062502 (2009)
12. W. Reisdorf et al., Systematics of pion emission in heavy ion collisions in the 1AGeV regime.
Nucl. Phys. A 781, 459–508 (2007)