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Search Results: 1 - 10 of 133472 matches for " Bao-An Li "
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Revisit of Coulomb effects on pi^{-}/pi^{+} ratio in heavy-ion collisions
Bao-An Li
Physics , 1995, DOI: 10.1016/0370-2693(95)00010-I
Abstract: It is shown that the large $\pi^{-}/\pi^{+}$ ratio at low pion energies recently observed in the reaction of Au+Au at $E_{beam}/A=1.0$ GeV at SIS/GSI is due to the strong Coulomb field of the reaction system.
Near-threshold $K^{+}$ Production in Heavy-ion Collisions
Bao-An Li
Physics , 1994, DOI: 10.1103/PhysRevC.50.2144
Abstract: Within a hadronic transport model we study in detail contributions to kaon yields and momentum spectra from various baryon (resonance)-baryon (resonance) and $\pi N$ interactions in heavy-ion collisions at beam energies near the free-space kaon production threshold. It is found that the finite lifetime of baryon resonances affects significantly the shape of kaon spectra, and the high energy parts of the kaon spectra are dominated by kaons from $\pi N\rightarrow \Lambda K^{+}$ processes. $N^{*}(1440)$ resonances are found to contribute about 10\% to the kaon yield. Effects of boosting the Fermi momentum distributions of the two colliding nuclei into their center of mass frame, centrality of the reaction as well as the nuclear equation of state on kaon yields and spectra are also discussed. Model calculations on $K^{+}$, $\pi^{+}$ and $\pi^{-}$ spectra for the reaction of Au+Au at $E_{beam}/A= 1.0$ GeV are compared with the experimental data from the KaoS collaboration.
High Density Behaviour of Nuclear Symmetry Energy and High Energy Heavy-Ion Collisions
Bao-An Li
Physics , 2002, DOI: 10.1016/S0375-9474(02)01018-7
Abstract: High energy heavy-ion collisions are proposed as a novel means to obtain information about the high density ({\rm HD}) behaviour of nuclear symmetry energy. Within an isospin-dependent hadronic transport model using phenomenological equations of state ({\rm EOS}) for dense neutron-rich matter, it is shown that the isospin asymmetry of the HD nuclear matter formed in high energy heavy-ion collisions is determined mainly by the HD behaviour of nuclear symmetry energy. Experimental signatures in several sensitive probes, i.e., $\pi^-$ to $\pi^+$ ratio, transverse collective flow and its excitation function as well as neutron-proton differential flow, are investigated. A precursor of the possible isospin separation instability in dense neutron-rich matter is predicted to appear as the local minima in the excitation functions of the transverse flow parameter for both neutrons and protons above the pion production threshold. Because of its {\it qualitative} nature unlike other {\it quantitative} observables, this precursor can be used as a unique signature of the isospin dependence of the nuclear {\rm EOS}. Measurements of these observables will provide the first terrestrial data to constrain stringently the HD behaviour of nuclear symmetry energy and thus also the {\rm EOS} of dense neutron-rich matter. Implications of our findings to neutron star studies are also discussed.
Probing the high-density behavior of nuclear symmetry energy with high-energy radioactive beams
Bao-An Li
Physics , 2003, DOI: 10.1016/S0375-9474(03)01360-5
Abstract: Central collisions induced by high energy radioactive beams can be used as a novel means to obtain crucial information about the high density ({\rm HD}) behaviour of nuclear symmetry energy. This information is critical for understanding several key issues in astrophysics. Within an isospin-dependent hadronic transport model using phenomenological equations of state ({\rm EOS}) for dense neutron-rich matter, we investigate several experimental probes of the HD behavior of nuclear symmetry energy, such as, the $\pi^-$ to $\pi^+$ ratio, neutron-proton differential flow and its excitation function. Measurements of these observables will provide the first terrestrial data to constrain stringently the HD behaviour of nuclear symmetry energy and thus also the {\rm EOS} of dense neutron-rich matter.
Observable effects of symmetry energy in heavy-ion collisions at RIA energies
Bao-An Li
Physics , 2003, DOI: 10.1103/PhysRevC.69.034614
Abstract: Within an isospin-dependent transport model for nuclear reactions induced by neutron-rich nuclei, we perform a comparative study of $^{100}Sn+^{124}Sn$ and $^{100}Zn+^{124}Sn$ reactions at beam energies of 30 MeV/A and 400 MeV/A to identify optimal experimental conditions and observables for investigating the equation of state (EOS) of neutron-rich matter at RIA. Several observables known to be sensitive to the density-dependence of the symmetry energy are examined as a function of impact parameter for both reaction systems. In particular, the strength of isospin transport/diffusion is studied by using rapidity distributions of free nucleons and their isospin asymmetries. An approximate isospin equilibrium is established even for peripheral collisions with a very soft symmetry energy at 30 MeV/A. At 400 MeV/A, however, a strong isospin translucency is observed even in most central collisions with either soft or stiff symmetry energies. Origins of these observations and their implications to determining the EOS of neutron-rich matter at the Rare Isotope Accelerator (RIA) are discussed.
Probing the EOS of dense neutron-rich matter with high-energy radioactive beams
Bao-An Li
Physics , 2003, DOI: 10.1016/j.nuclphysa.2004.01.109
Abstract: Nuclear reactions induced by high energy radioactive beams create a transient state of nuclear matter with high density and appreciable neutron to proton asymmetry. This will provide a unique opportunity to explore novel properties of dense neutron-rich matter and the isospin-dependence of the nuclear equation of state (EOS). Here we study the $\pi^-/\pi^+$ ratio as a probe of the EOS of dense neutron-rich matter.
Isospin-Dependence of $π^-/π^+$ Ratio and Density-Dependence of Nuclear Symmetry Energy
Bao-An Li
Physics , 2002, DOI: 10.1103/PhysRevC.67.017601
Abstract: The $\pi^-/\pi^+$ ratio is examined as a function of isospin asymmetry and beam energy for central collisions induced by neutron-rich nuclei within an isospin-dependent hadronic transport model. The $\pi^-/\pi^+$ ratio is found to increase with the isospin asymmetry, but decrease with the beam energy of the reaction. For neutron-rich systems, such as, $^{124}Sn+^{124}Sn$ and $^{132}Sn+^{124}Sn$, the sensitivity of $\pi^-/\pi^+$ ratio to nuclear symmetry energy is almost beam energy independent.
Uranium on uranium collisions at relativistic energies
Bao-An Li
Physics , 1999, DOI: 10.1103/PhysRevC.61.021903
Abstract: Deformation and orientation effects on compression, elliptic flow and particle production in uranium on uranium collisions (UU) at relativistic energies are studied within the transport model ART. The density compression in tip-tip UU collisions is found to be about 30% higher and lasts approximately 50% longer than in body-body or spherical UU reactions. The body-body UU collisions have the unique feature that the nucleon elliptic flow is the highest in the most central collisions and remain a constant throughout the reaction. We point out that the tip-tip UU collisions are more probable to create the QGP at AGS and SPS energies while the body-body UU collisions are more useful for studying properties of the QGP at higher energies.
Constraining the neutron-proton effective mass splitting in neutron-rich matter
Bao-An Li
Physics , 2004, DOI: 10.1103/PhysRevC.69.064602
Abstract: Within Bombaci's phenomenological single-nucleon potential model we study the neutron-proton effective mass splitting $m_n^*- m_p^*$ in neutron-rich matter. It is shown that an effective mass splitting of $m_n^*
Neutron-Proton Differential Flow as a Probe of Isospin-Dependence of Nuclear Equation of State
Bao-An Li
Physics , 2000, DOI: 10.1103/PhysRevLett.85.4221
Abstract: The neutron-proton differential flow is shown to be a very useful probe of the isospin-dependence of the nuclear equation of state (EOS). This novel approach utilizes constructively both the isospin fractionation and the nuclear collective flow as well as their sensitivities to the isospin-dependence of the nuclear EOS. It also avoids effectively uncertainties associated with other dynamical ingredients of heavy-ion reactions at intermediate energies.
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