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.
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
124137012
Study of in-medium Delta Delta elastic scattering cross section
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.
117742966
Non-equilibrium dynamics in heavy ion collisions at low SIS energies
The Ultrarelativistic Quantum Molecular Dynamics (UrQMD) model, a microscopic transport model, is used to study the directed and elliptic collective flows and the nuclear stopping in Au+Au collisions at incident energies covered by INDRA and lower-energy FOPI experiments. It is seen clearly that these observables are sensitive to both, the potential terms (including iso-scalar and iso-vector parts as well as the momentum dependent term) in the equation of state (EoS) and the collision term (including the Pauli-blocking and the medium-modified nucleon-nucleon elastic cross section (NNECS)). The momentum modifications of both, the mean-field potentials and the density dependent NNECS, are found to be sensitive to the collectivity of heavy-ion collisions. At INDRA energies ($\le 150$~MeV/nucleon), the dynamic transport with a soft EoS with momentum dependence and with the momentum-modified density-dependent NNECS describes the directed flow exhibited by hydrogen isotopes ($Z=1$) emitted at mid-rapidity fairly well.
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.
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.
15616620
Nonperturbative effect in threshold resummation
We show that the conventional threshold resummation calculation cannot describe well the low energy Drell-Yan (DY) data without including the non-perturbative correction terms which are deduced from analyzing the asymptotic behavior of the resummation formalism. It is demonstrated that the non-perturbative correction is generally small for the large invariant mass DY pairs produced at the Tevatron and the LHC.
55221705
Measurement of decay time of liquid scintillator
In this paper we describe a single photon method to measure the decay time of two kinds of homemade liquid scintillator. We find that the fast and slow decay time constants of these two samples, with 5cm diameter and 4cm height, are about similar to 4ns and similar to 17ns, respectively. These results are checked through a reference measurement by recording the scintillation pulse shapes at the output of a fast response PMT directly by a digital oscilloscope. The time responses of these two samples are as good as those of commercial liquid scintillator. (C) 2008 Elsevier B.V. All rights reserved.
118411931
Temperature dependence of single-particle properties in nuclear matter
The single-nucleon potential in hot nuclear matter is investigated in the framework of the Brueckner theory by adopting the realistic Argonne V{sub 18} or Nijmegen 93 two-body nucleon-nucleon interaction supplemented by a microscopic three-body force. The rearrangement contribution to the single-particle potential induced by the ground state correlations is calculated in terms of the hole-line expansion of the mass operator and provides a significant repulsive contribution in the low-momentum region around and below the Fermi surface. Increasing temperature leads to a reduction of the effect, while increasing density makes it become stronger. The three-body force suppresses somewhat the ground state correlations due to its strong short-range repulsion, increasing with density. Inclusion of the three-body force contribution results in a quite different temperature dependence of the single-particle potential at high enough densities as compared to that adopting the pure two-body force. The effects of three-body force and ground state correlations on the nucleon effective mass are also discussed.
15695185
Systematic study on QCD interactions of heavy mesons with ρ meson
Abstract The strong interactions of the negative-parity heavy mesons with ρ meson may be described consistently in the context of an effective Lagrangian, which is invariant under isospin SU ( 2 ) transformation. Four coupling constants g H H ρ , f H ∗ H ρ , g H ∗ H ∗ ρ and f H ∗ H ∗ ρ enter the effective Lagrangian, where H ( H ∗ ) denotes a pseudoscalar bottom or charm meson (the corresponding vector meson). Using QCD light cone sum rule (LCSR) method and, as inputs, the hadronic parameters updated recently, we give an estimate of g H ∗ H ∗ ρ and f H ∗ H ∗ ρ , about which little was known before, and present an improved result for g H H ρ and f H ∗ H ρ . Also, we examine the heavy quark asymptotic behavior of these nonperturbative quantities and assess the two low energy parameters β and λ of the corresponding effective chiral Lagrangian.