122275477
Analysis of intermediate energy proton-induced spallation reactions by an improved quantum molecular dynamics plus statistical decay model
Intermediate energy proton-induced spallation reactions with various targets are studied by the improved quantum molecular dynamics (ImQMD05) model incorporated with the statistical decay model. The influences of the different Skyrme interactions on the mechanism of spallation reaction and the double differential cross sections of emitted neutrons are studied. It is found that the different Skyrme interactions influence the low energy part of spectrum of emitted neutrons. This effect decreases as incident energy becomes higher. The double differential cross sections of emitted neutrons are found to be in good agreement with experimental data when the Skyrme parameter set SkP is adopted.
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.
124137012
Study of in-medium Delta Delta elastic scattering cross section
119408968
Isospin dependence of nucleon-nucleon elastic cross section
The in-medium neutron-proton, proton-proton (neutron-neutron) scattering cross sections (sigma(np)*, sigma(pp(nn))*) are studied based on QHD-II type Lagangian within the framework of the microscopic transport theory. The results demonstrate that, for free nucleon-nucleon scattering cross sections, the isospin dependence is dominantly caused by the rho meson field. The medium correction of nucleon-nucleon scattering cross sections is also isospin dependent, sigma(np)*, depends on the baryon density weakly and sigma(pp(nn))* depends on the baryon density significantly, which is due to the different effects of the medium correction of nucleon mass and rho meson mass on sigma(np) and sigma(pp(nn)), respectively.
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
121143863
THE DYNAMICAL ISOSPIN EFFECT ON PROTON-INDUCED REACTIONS ON Sn ISOTOPES
In this talk we present a model, Improved Quantum Molecular Dynamics (ImQMD05) model incorporated with a Statistical Decay Model (SDM), to describe intermediate energy proton induced spallation reactions. A good agreement with experimental data of double differential cross sections of emitted neutrons is obtained. We further apply this model to study the isospin effect in proton induced spallation reactions on a series Sn isotope targets. We find that the systematic behavior of the reaction cross sections for Sn isotope targets deviates from the empirical expression obtained by fitting the experimental data for proton induced spallation reactions on target nuclei along β-stability line. The extent of the deviation depends on the density dependence of the symmetry energy strongly. We also find an obvious shift of the elastic scattering angular distribution of emitted protons when the symmetry energy is taken into account for neutron-rich Sn isotope targets and the angle shifted strongly depends on the stiffness of the symmetry energy. The attractive effect of the symmetry potential of target on incident proton directly influences the motion of the incident proton leading to strong isospin effect on the reaction dynamics and thus on these reaction observables. We conclude that the measurement of reaction cross sections and the elastic scattering angular distributions in proton induced spallation reactions on Sn isotopes can provide clear constraint for the density dependence of symmetry energy.
119196192
THE VERTICAL X-SHAPED STRUCTURE IN THE MILKY WAY: EVIDENCE FROM A SIMPLE BOXY BULGE MODEL
A vertical X-shaped structure in the Galactic bulge was recently reported. Here, we present evidence of a similar X-shaped structure in the Shen et al. 2010 bar/boxy bulge model that simultaneously matches the stellar kinematics successfully. The X-shaped structure is found in the central region of our bar/boxy bulge model and is qualitatively consistent with the observed one in many aspects. End-to-end separations of the X-shaped structure in the radial and vertical directions are roughly 3 kpc and 1.8 kpc, respectively. The X-shaped structure contains about 7% of light in the boxy bulge region, but it is significant enough to be identified in observations. An X-shaped structure naturally arises in the formation of bar/boxy bulges and is mainly associated with orbits trapped around the vertically extended x{sub 1} family. Like the bar in our model, the X-shaped structure tilts away from the Sun-Galactic center line by 20 Degree-Sign . The X-shaped structure becomes increasingly symmetric about the disk plane, so the observed symmetry may indicate that it formed at least a few billion years ago. The existence of the vertical X-shaped structure suggests that the formation of the Milky Way bulge is shaped mainly by internal disk dynamical instabilities.
16718501
The Kaon-Photoproduction Of Nucleons In The Chiral Quark Model
In this paper, we develop a general framework to study the mesonphotoproductions of nucleons in the chiral quark model. The S and U channel resonance contributions are expressed in terms of the ChewGoldberger-Low-Nambu (CGLN) amplitudes. The kaon-photoproduction processes, γp → K+Λ, γp → K+Σ0, and γp → K0Σ+, are calculated. The initial results show that the quark model provides a much improved description of the reaction mechanism for the kaon-photoproductions of the nucleon with less parameters than the traditional phenomenological approaches. PACS numbers: 13.75.Gx, 13.40.Hq, 13.60.Le,12.40.Aa
119264529
Next-to-leading order QCD effects in associated charged Higgs and W boson production in the MSSM at the CERN Large Hadron Collider
We present the calculations of the next-to-leading order (NLO) QCD corrections to the inclusive total cross sections for the associated production of the ${W}^{\ifmmode\pm\else\textpm\fi{}}{H}^{\ensuremath{\mp}}$ through $b\overline{b}$ annihilation in the minimal supersymmetric standard model at the CERN Large Hadron Collider. The NLO QCD corrections can either enhance or reduce the total cross sections, but they generally efficiently reduce the dependence of the total cross sections on the renormalization/factorization scale. The magnitude of the NLO QCD corrections is about 10% in most of the parameter space and can reach 15% in some parameter regions. We also show the Monte Carlo simulation results for the $2j+{\ensuremath{\tau}}_{\mathrm{jet}}+{\mathrm{p\ensuremath{\llap{\not\;}}}}_{T}$ signature from the ${W}^{\ifmmode\pm\else\textpm\fi{}}$ and the ${H}^{\ensuremath{\mp}}$ decays including the NLO QCD effects, and find an observable signal at a $5\ensuremath{\sigma}$ level in some parameter region of the minimal supergravity model.
118678837
Understanding the X-ray spectrum of anomalous X-ray pulsars and soft gamma-ray repeaters*
Hard X-rays above 10 keV are detected from several anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs), and different models have been proposed to explain the physical origin within the frame of either a magnetar model or a fallback disk system. Using data from Suzaku and INTEGRAL, we study the soft and hard X-ray spectra of four AXPs/SGRs: 1RXS J170849-400910, 1E 1547.0-5408, SGR 1806-20 and SGR 0501+4516. It is found that the spectra could be well reproduced by the bulk-motion Comptonization (BMC) process as was first suggested by Trumper et al., showing that the accretion scenario could be compatible with Xray emission from AXPs/SGRs. Simulated results from the Hard X-ray Modulation Telescope using the BMC model show that the spectra would have discrepancies from the power-law, especially the cutoff at similar to 200 keV. Thus future observations will allow researchers to distinguish different models of the hard X-ray emission and will help us understand the nature of AXPs/SGRs.
4046382
Nuclear symmetry potential in the relativistic impulse approximation
Using the relativistic impulse approximation with the Love-Franey NN scattering amplitude developed by Murdock and Horowitz, we investigate the low-energy (100{<=}E{sub kin}{<=}400 MeV) behavior of the nucleon Dirac optical potential, the Schroedinger-equivalent potential, and the nuclear symmetry potential in isospin asymmetric nuclear matter. We find that the nuclear symmetry potential at fixed baryon density decreases with increasing nucleon energy. In particular, the nuclear symmetry potential at saturation density changes from positive to negative values at nucleon kinetic energy of about 200 MeV. Furthermore, the obtained energy and density dependence of the nuclear symmetry potential is consistent with those of the isospin- and momentum-dependent MDI interaction with x=0, which has been found to describe reasonably well both the isospin diffusion data from heavy-ion collisions and the empirical neutron-skin thickness of {sup 208}Pb.