K Wang

Examining the exotic structure of the proton-rich nucleus {sup 23}Al

The longitudinal momentum distribution (P{sub //}) of fragments after one-proton removal from {sup 23}Al and reaction cross sections ({sigma}{sub R}) for {sup 23,24}Al on a carbon target at 74A MeV have been measured. The {sup 23,24}Al ions were produced through projectile fragmentation of 135A MeV {sup 28}Si primary beam using the RIPS fragment separator at RIKEN. P{sub parallel} is measured by a direct time-of-flight (TOF) technique, while {sigma}{sub R} is determined using a transmission method. An enhancement in {sigma}{sub R} is observed for {sup 23}Al compared with {sup 24}Al. The P{sub parallel} for {sup 22}Mg fragments from {sup 23}Al breakup has been obtained for the first time. FWHM of the distributions has been determined to be 232 {+-} 28 MeV/c. The experimental data are discussed by using the Few-Body Glauber model. Analysis of P{sub //} demonstrates a dominant d-wave configuration for the valence proton in ground state of {sup 23}Al, indicating that {sup 23}Al is not a proton halo nucleus.

Scaling of anisotropic flow and momentum-space densities for light particles in intermediate energy heavy ion collisions

Abstract Anisotropic flows ( v 2 and v 4 ) of light nuclear clusters are studied by isospin-dependent quantum molecular dynamics model for the system of 86 Krxa0+xa0 124 Sn at intermediate energy and large impact parameters. Number-of-nucleon scaling of the elliptic flow ( v 2 ) are demonstrated for the light fragments up to A = 4 , and the ratio of v 4 / v 2 2 shows a constant value of 1/2. In addition, the momentum-space densities of different clusters are also surveyed as functions of transverse momentum, in-plane transverse momentum and azimuth angle relative to the reaction plane. The results can be essentially described by momentum-space power law. All the above phenomena indicate that there exists a number-of-nucleon scaling for both anisotropic flow and momentum-space densities for light clusters, which can be understood by the coalescence mechanism in nucleonic degree of freedom for the cluster formation.

Isospin effect in statistical sequential decay

Isospin effect of the statistical emission fragments from the equilibrated source is investigated in the frame of statistical binary decay implemented into the GEMINI code, isoscaling behavior is observed and the dependences of isoscaling parameters alpha and beta on emission fragment size, source size, source isospin asymmetry and excitation energies are studied. Results show that alpha and beta neither depends on light fragment size nor on source size. A good linear dependence of alpha and beta on the inverse of temperature T is manifested and the relationship of alpha=4C(sym)[(Z(s)/A(s))(1)(2)-(Z(s)/A(s))(2)(2)]/T and beta=4C(sym)[(N-s/A(s))(1)(2)-(N-s/A(s))(2)(2)]/T from different isospin asymmetry sources is satisfied. The symmetry energy coefficient C-sym extracted from simulation results is similar to 23 MeV which includes both the volume and surface term contributions, of which the surface effect seems to play a significant role in the symmetry energy.

Surveying the nucleon-nucleon momentum correlation function in the framework of quantum molecular dynamics model

Momentum correlation functions of nucleon-nucleon pairs are presented for reactions with C isotopes bombardinga 12 Ctargetwithintheframeworkoftheisospin-dependentquantummolecular dynamics model.The binding-energy dependence of the momentum correlation functions is also explored, and other factors that have an influence on momentum correlation functions are investigated. These factors include momentum-dependent nuclear equations of state, in-medium nucleon-nucleon cross sections, impact parameters, total pair momenta, and beam energy. In particular, the rise and the fall of the strength of momentum correlation functions at lower relative momentum are shown with an increase in beam energy.

Isoscaling behavior in fission dynamics

The fission processes of 112 Sn + 112 Sn and 116 Sn + 116 Sn are simulated with the combination of the Langevin equation and the statistical decay model. The masses of two fission fragments are given by assuming the process of symmetric fission or asymmetric fission by the Monte Carlo sampling with the Gaussian probability distribution. From the analysis to the isotopic/isotonic ratios of the fission fragments from both reactions, the isoscaling behavior has been observed and investigated

Systematic study of isoscaling behavior in projectile fragmentation by the statistical abrasion–ablation model

The isospin effect and isoscaling behavior in projectile fragmentation have been systematically investigated by a modified statistical abrasion–ablation (SAA) model. The normalized peak differences and reduced isoscaling parameters are found to decrease with (Zproj − Z)/Zproj or the excitation energy per nucleon and have no significant dependence on the size of reaction systems. Assuming a Fermi-gas behavior, the excitation energy dependence of the symmetry energy coefficients is tentatively extracted from α and β which looks consistent with the experimental data. It is pointed out that the reduced isoscaling parameters can be used as an observable to study excitation extent of system and asymmetric nuclear equation of state in heavy ion collisions.

Scaling of anisotropy flows in intermediate energy heavy ion collisions

Anisotropic flows ( v 1 , v 2 and v 4 ) of light nuclear clusters are studied by a nucleonic transport model in intermediate energy heavy ion collisions. The number-of-nucleon scalings of the directed flow ( v 1 ) and elliptic flow ( v 2 ) are demonstrated for light nuclear clusters. Moreover, the ratios of v 4 / v 2 2 of nuclear clusters show a constant value of 1/2 regardless of the transverse momentum. The above phenomena can be understood by the coalescence mechanism in nucleonic level and are worthy to be explored in experiments.

Azimuthal asymmetry of direct photons in intermediate energy heavy-ion collisions

Hard photon emitted from energetic heavy ion collisions is of very interesting since it does not experience the late-stage nuclear interaction, therefore it is useful to explore the early-stage information of matter phase. In this work, we have presented a first calculation of azimuthal asymmetry, characterized by directed transverse flow parameter F and elliptic asymmetry coefficient v(2), for proton-neutron bremsstrahlung hard photons in intermediate energy heavy-ion collisions. The positive F and negative v(2) of direct photons are illustrated and they seem to be anti-correlated to the corresponding free protons flow. (c) 2008 Elsevier B.V. All rights reserved.

Investigations on light proton-rich nuclei with exotic structure

Abstract One of the proton halo candidates 23Al and its isotopes are systematically investigated in the nonlinear Relativistic Mean-Field and Skyrme Hartree-Fock approaches. It is shown that there exists the energy inversion of ( 5 2 ) + (202) and ( 1 2 ) + (211) orbitals in 23Al nucleus and which may produce the large enhancement of reaction cross section comparing with its neighboring nuclei. Meanwhile, it is obvious to see that the isospin effect of the pairing correlation plays a great role to the separation energy when the Al isotopes approach to the proton drip line. In addition, the ground state and excited state of 9B, 13N are also investigated in the RMF model. There may exist the halo structure in 13N when the last proton of 13N occupies in the first excited state.

Nucleon-nucleon momentum correlation function for light nuclei

Nucleon-nucleon momentum correlation function have been presented for nuclear reactions with neutron-rich or proton-rich projectiles using a nuclear transport theory, namely Isospin-Dependent Quantum Molecular Dynamics model. The relationship between the binding energy of projectiles and the strength of proton-neutron correlation function at small relative momentum has been explored, while proton-proton correlation function shows its sensitivity to the proton density distribution. Those results show that nucleon-nucleon correlation function is useful to reflect some features of the neutron- or proton-halo nuclei and therefore provide a potential tool for the studies of radioactive beam physics.