Reexamination of the neutron-to-proton-ratio puzzle in intermediate-energy heavy-ion collisions

2015/02/28 by Hai-Yun Kong, Yin Xia, Jun Xu +4 · 31 citations
Earth and Planetary Sciences · Physics and Astronomy · #Atomic physics #Energy (signal processing) #Heavy ion #High-pressure geophysics and materials #Ion #Isospin #Neutron #Nuclear physics #Nuclear physics research studies #Nucleon #Physics #Proton #Quantum Chromodynamics and Particle Interactions #nucl-ex #nucl-th

paper · pdf · doi:10.1103/physrevc.91.047601

published in Physical Review C 91(4) (American Institute of Physics) · 6 pages, 2 figures, discussions added

arxiv created 2015/04/02 · openalex publication_date 2015/04/14 · arxiv updated 2015/04/16 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05

Abstract

Incorporating a newly improved isospin- and momentum-dependent interaction in the isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model IBUU11, we have investigated relative effects of the density dependence of nuclear symmetry energy E_sym(\ensuremathρ) and the neutron-proton effective mass splitting m_n^*\ensuremath-m_p^* on the neutron-to-proton ratio of free nucleons and those in light clusters. It is found that the m_n^*\ensuremath-m_p^* has a relatively stronger effect than the E_sym(\ensuremathρ) and the assumption of m_n^*\ensuremath≤m_p^* leads to a higher neutron-to-proton ratio. Moreover, this finding is independent of the in-medium nucleon-nucleon cross sections used. However, results of our calculations using the E_sym(\ensuremathρ) and m_n^*\ensuremath-m_p^* both within their current uncertainty ranges are all too low compared to the recent National Superconducting Cyclotron Laboratory double neutron-to-proton-ratio data from central ¹²⁴Sn+¹²⁴Sn and ¹¹²Sn+¹¹²Sn collisions at 50 and 120 MeV/u, thus calling for new mechanisms to explain the puzzlingly high neutron-to-proton ratio observed in the experiments.

Citations

• Effective Nucleon Masses in Symmetric and Asymmetric Nuclear Matter
• PRIMORDIAL NUCLEOSYNTHESIS: SUCCESSES AND CHALLENGES
• Isospin asymmetry in nuclei and neutron stars

Cited by

• Thermal properties of hot and dense matter with finite range interactions
• Impact parameter smearing effects on isospin sensitive observables in heavy ion collisions

Related

• Investigation of the neutron-proton effective mass splitting via heavy ion collisions: Constraints and Implications
• Equation of state of nuclear matter from collective flows and stopping in intermediate energy heavy-ion collisions
• Constraints on the density dependence of the symmetry energy from heavy ion collisions
• Ab initio calculation of the neutron-proton mass difference
• Constraining the density dependence of the symmetry energy: the isospin transport ratio revisited