D. Q. Fang

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.

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.

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.

Study of incident energy and isospin dependencies of total reaction cross section via the BUU model

The incident energy and isospin dependencies of total reaction cross sections sigma(R) have been researched by using the Boltzmann-Uehling-Uhlenbeck (BUU) model. When the width parameter of square-type or 140-type density distribution is obtained by fitting the sigma(R) at relativistic energies, the calculated result with BUU-model can reproduce the experimental data at intermediate energies better than that with Glauber-model of optical limit approximation. The systematical underestimation of sigma(R) at intermediate energy was removed out by BUU calculation framework. It is found that sigma(R) is sensitive to nuclear equation of state (EOS). It is also found that the difference factor (d) defined in text is sensitive to the nuclear structure such as neutron halo and neutron skin, etc

Measurements of the reaction cross sections and momentum distributions for 23Al neighbouring nuclei

The reaction cross sections and momentum distributions for 23Al and its neighbouring nuclei have been measured at the Riken Projectile Fragment Separator (RIPS). The primary beam of 135 A MeV 28Si was used to produce the secondary beams. The measurement of σR was carried out by using a transmission‐type method, σR was determined by the ratios between incident and outgoing particles without reaction from both target‐in and target‐out measurements. P// of fragment from breakup reactions was determined from the measured TOF between F2 and F3. An enhancement is observed in σR for 23Al compared to its neighbors. The P// of 22Mg fragments from 23Al breakup have been obtained. The width of the distributions is found to be consistent with prediction by the Goldhaber Model. The experimental data are discussed in the framework of Glauber model. The analysis of P// indicates a dominant d‐wave component in the ground state of 23Al. This confirms the result of a recent magnetic moment measurement which indicates that ...

Measurements of total reaction cross sections for neutron-deficient nuclei (A < 30) and investigation on possible proton halo nuclei

Measurements of total reaction cross sections (σR) for some proton-rich nuclei (N=10∼15 isotones) on carbon target at intermediate energies have been performed on RIBLL of HIRFL. A larger enhancement of the σR for 27P and 23Al has been observed than for its neighboring nuclei. Density distributions for 27P have been extracted from the measured σR data within the framework of the Glauber model. A proton halo in 27P and 23Al is demonstrated.

Isospin effect on particle emission in nuclear dissociation

The isospin effect of particle emission for disassembling isotopic sources of 122,129,137,146Xe and for isobaric sources of 129La, 129Xe, 129Sb and 129Cd are explored in the framework of the isospin-dependent lattice gas model. The multiplicity of emitted particles, the isotopic and isobaric ratios of light particles show the strong dependence on the isospin of the dissociation source, but the double ratios of light isotopes are insensitive to the isospin. The former directly reflects the chemical composition and the latter indicates the chemical equilibrium of the source. In addition, the slopes of the average multiplicities of emitted particles to temperature and the variances of the multiplicity distributions of emitted particles are suggested as additional judgements to the critical behaviour. The critical temperatures deduced from the above slopes and variances are found to be insensitive to the isospin of the disassembling sources.