8355559
Improved quantum molecular dynamics model and its applications to fusion reaction near barrier
An improved quantum molecular dynamics model is developed. By using this model, the properties of ground state of nuclei from Li-6 to Pb-208 are described very well with one set of parameters. The fusion reactions for Ca-40+Zr-90, Ca-40+Zr-96, and Ca-48+Zr-90 at energies near the barrier are studied by this model. The experimental data of the fusion cross sections for Ca-40+Zr-90,Zr-96 at energies near the barrier are reproduced remarkably well without introducing any new parameters. The mechanism for the enhancement of the fusion cross sections for neutron-rich nuclear reaction near barrier is analyzed.
43357197
Probing equilibration with respect to isospin degree of freedom in intermediate energy heavy ion collisions
We have studied equilibration with respect to isospin degree of freedom in four 96 mass systems Ru-96 + Ru-96, Ru-96 + Zr-96, Zr-96 + Ru-96, and Zr-96 + Zr-96 at 100A MeV and 400A MeV with isospin-dependent quantum molecular dynamics. We propose that the neutron-proton differential rapidity distribution is a sensitive probe to the degree of equilibration with respect to the isospin degree of freedom. By analyzing the average N/Z ratio of emitted nucleons, light charged particles, and intermediate mass fragments (IMF), it is found that there exist memory effect in multi fragmentation process. The average N/Z ratio of IMF reduces largely as beam energy increases from 100A MeV to 400A MeV that may result from the change of the behavior of the isotope distribution of IMF charges. The isotope distribution of IMF charges does also show certain memory effect at 100A MeV case but not at 400A MeV case.
124137012
Study of in-medium Delta Delta elastic scattering cross section
9051613
Mass and isotope dependence of limiting temperatures for hot nuclei
The mass and isotope dependence of limiting temperatures for hot nuclei are investigated. The predicted mass dependence of limiting temperatures is in good agreement with data derived from the caloric curve data. The predicted isotope distribution of limiting temperatures appears to be a parabolic shape and its centroid is not located at the isotope on the beta-stability line (T=0) but at neutron-rich side. Our study shows that the mass and isotope dependence of limiting temperatures depend on the interaction and the form of surface tension and its isospin dependence sensitively.
55892113
In-medium NN cross sections determined from stopping and collective flow in intermediate-energy heavy-ion collisions
In-medium nucleon-nucleon scattering cross sections are explored by comparing results of quantum molecular dynamics simulations to data on stopping and on elliptic and directed flow in intermediate-energy heavy-ion collisions. The comparison points to in-medium cross sections which are suppressed at low energies but not at higher energies. Positive correlations are found between the degree of stopping and the magnitudes of elliptic and directed flows. PACS numbers: 25.70.-z, 24.10.Lx, 21.65.+f
118996027
Production and rescattering of strange baryons at SPS energies in a transport model with hadron potentials
A mean-field potential version of the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model is used to investigate the production of strange baryons, especially the $\Lambda$s and $\overline{\Lambda}$s, from heavy ion collisions at SPS energies. It is found that, with the consideration of both formed and pre-formed hadron potentials in UrQMD, the transverse mass and longitudinal rapidity distributions of experimental data of both $\Lambda$s and $\overline{\Lambda}$s can be quantitatively explained fairly well. Our investigation also shows that both the production mechanism and the rescattering process of hadrons play important roles in the final yield of strange baryons.
118612358
THE CARNEGIE-IRVINE GALAXY SURVEY. III. THE THREE-COMPONENT STRUCTURE OF NEARBY ELLIPTICAL GALAXIES
Motivated by recent developments in our understanding of the formation and evolution of massive galaxies, we explore the detailed photometric structure of a representative sample of 94 bright, nearby elliptical galaxies, using high-quality optical images from the Carnegie-Irvine Galaxy Survey. The sample spans a range of environments and stellar masses, from M * = 1010.2 to 1012.0 M ☉. We exploit the unique capabilities of two-dimensional image decomposition to explore the possibility that local elliptical galaxies may contain photometrically distinct substructure that can shed light on their evolutionary history. Compared with the traditional one-dimensional approach, these two-dimensional models are capable of consistently recovering the surface brightness distribution and the systematic radial variation of geometric information at the same time. Contrary to conventional perception, we find that the global light distribution of the majority (75%) of elliptical galaxies is not well described by a single Sersic function. Instead, we propose that local elliptical galaxies generically contain three subcomponents: a compact (Re 1 kpc) inner component with luminosity fraction f 0.1-0.15; an intermediate-scale (Re 2.5 kpc) middle component with f 0.2-0.25; and a dominant (f = 0.6), extended (Re 10 kpc) outer envelope. All subcomponents have average Sersic indices n 1-2, significantly lower than the values typically obtained from single-component fits. The individual subcomponents follow well-defined photometric scaling relations and the stellar mass-size relation. We discuss the physical nature of the substructures and their implications for the formation of massive elliptical galaxies.
118623641
Threshold resummation effects in neutral Higgs boson production by bottom quark fusion at the CERN Large Hadron Collider
We investigate the QCD effects in the production of neutral Higgs bosons via bottom quark fusion in both the standard model and the minimal supersymmetric standard model at the CERN Large Hadron Collider. We include the next-to-leading order (NLO) QCD corrections (including supersymmetric QCD) and the threshold resummation effects. We use the soft-collinear effective theory to resum the large logarithms near threshold from soft gluon emission. Our results show that the resummation effects can enhance the total cross sections by about 5% compared with the NLO results.
119339630
Quark model study of the eta photoproduction: Evidence for a new S(11) resonance?
An extensive and systematic study of the recent eta photoproduction data up to 1.2 GeV is presented within a chiral constituent quark model. A model embodying all known nucleonic resonances shows clear need for a yet undiscovered third S11 resonance in the second resonance region, for which we determine the mass (1.729 GeV) and the total width (183 MeV). Furthermore, we extract the configuration mixing angles, an important property of the quark-quark interaction in the quark model, for the resonances S11(1535) and S11(1650), as well as for the resonances D13(1520) and D13(1700). Our results agree well with the quark model predictions. In addition, the partial eta N decay widths and/or the photo-excitation helicity amplitudes for the nucleonic resonances S11(1535), S11(1650), P11(1710), P13(1720), D13(1520), D13(1700), D15(1675), and F15(1680) are also obtained in this approach.
55468935
Microscopic analysis of order parameters in nuclear quantum phase transitions
Microscopic signatures of nuclear ground-state shape phase transitions in Nd isotopes are studied using excitation spectra and collective wave functions obtained by diagonalization of a five-dimensional Hamiltonian for quadrupole vibrational and rotational degrees of freedom, with parameters determined by constrained self-consistent relativistic mean-field calculations for triaxial shapes. As a function of the physical control parameter, the number of nucleons, energy gaps between the ground state and the excited vibrational states with zero angular momentum, isomer shifts, and monopole transition strengths exhibit sharp discontinuities at neutron number N=90, which is characteristic of a first-order quantum phase transition.
119073126
Improved approach to the heavy to light form-factors in the light cone QCD sum rules
A systematic analysis shows that the main uncertainties in the form factors are due to the twist-3 wave functions of the light mesons in the light-cone QCD sum rules. We propose an improved approach, in which the twist-3 wave functions do not make any contribution and therefore the possible pollution by them can be avoided, to reexamine B-->pi semileptonic form factors. Also, a comparison between previous results and our results from the light-cone QCD sum rules is made. Our method will be beneficial to the precise extraction of \V-ub\ from the experimental data on the processes B-->pil )over tilde>(l).