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Register a new userObservable to explore high density behaviour of symmetry energy
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Authors
Aman D. Sood
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We aim to see the sensitivity of collective transverse in-plane flow to symmetry energy at low as well as high densities and also to see the effect of different density dependencies of symmetry energy on the same.
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The $NDeltato NN$ cross sections, which take into account the $Delta$-mass dependence of M-matrix and momentum $p_{NDelta}$, are applied on the calculation of pion production within the framework of the UrQMD model. Our study shows that UrQMD calculations with the $Delta$-mass dependent $NDeltato NN$ cross sections enhance the pion multiplicities and decrease the $pi^-/pi^+$ ratios. By analyzing the time evolution of the pion production rate and the density in the overlapped region for Au+Au at the beam energy of 0.4A GeV, we find that the pion multiplicity probes the symmetry energy in the region of 1-2 times normal density. The process of pion production in the reaction is tracked including the loops of $NNleftrightarrow NDelta$ and $Deltaleftrightarrow Npi$, our calculations show that the sensitivity of $pi^-/pi^+$ to symmetry energy is weakened after 4-5 N-$Delta$-$pi$ loops in the pion production path, while the $pi^{-}/pi^{+}$ ratio in reactions at near threshold energies remains its sensitivity to the symmetry energy. By comparing the calculations to the FOPI data, we obtain a model dependent conclusion on the symmetry energy and the symmetry energy at two times normal density is $S(2rho_0)$=38-73 MeV within $1sigma$ uncertainties. Under the constraints of tidal deformability and maximum mass of neutron star, the symmetry energy at two times normal density is reduced to $48-58$ MeV and slope of symmetry energy $L=54-81$ MeV, and it is consistent with the constraints from ASY-EOS flow data.
The Charge-Symmetry-Breaking (CSB) character of the nucleon-nucleon interaction is well established. This work presents two different ways of introducing such effects into a nuclear Energy Density Functional (EDF). CSB terms are either coming from the effective theory expansion or are derived from electromagnetic mixing of $rho^0$ and $omega$ mesons. These terms are then introduced to Skyrme and Quark-Meson-Coupling EDFs, respectively.
The nuclear symmetry energy represents a response to the neutron-proton asymmetry. In this survey we discuss various aspects of symmetry energy in the framework of nuclear density functional theory, considering both non-relativistic and relativistic self-consistent mean-field realizations side-by-side. Key observables pertaining to bulk nucleonic matter and finite nuclei are reviewed. Constraints on the symmetry energy and correlations between observables and symmetry-energy parameters, using statistical covariance analysis, are investigated. Perspectives for future work are outlined in the context of ongoing experimental efforts.
We show that the notion of partial dynamical symmetry is robust and founded on a microscopic many-body theory of nuclei. Based on the universal energy density functional framework, a general quantal boson Hamiltonian is derived and shown to have essentially the same spectroscopic character as that predicted by the partial SU(3) symmetry. The principal conclusion holds in two representative classes of energy density functionals: nonrelativistic and relativistic. The analysis is illustrated in application to the axially-deformed nucleus $^{168}$Er.
The reaction mechanism of the central collisions and peripheral collisions for $^{112,124}Sn+^{112,124}Sn$ at $E/A=50MeV$ is investigated within the framework of the Improved Quantum Molecular Dynamics model. The results show that multifragmentation process is an important mechanism at this energy region, and the influence of the cluster emission on the double n/p ratios and the isospin transport ratio are important. Furthermore, three observables, double n/p ratios, isospin diffusion and the rapidity distribution of the ratio $R_{7}$ for $^{112,124}Sn+^{112,124}Sn$ at E/A=50MeV are analyzed with the Improved Quantum Molecular Dynamics model. The results show that these three observables are sensitive to the density dependence of the symmetry energy. By comparing the calculation results to the data, the consistent constraint on the density dependence of the symmetry energy from these three observables is obtained.
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