122313362
Hyperon coupling dependence of hadron matter properties in relativistic mean field model
The properties of hadronic matter at β equilibrium in a wide range of densities are described by appropriate equations of state in the framework of the relativistic mean field model. Strange meson fields, namely the scalar meson field σ* (975) and the vector meson field (1020), are included in the present work. We discuss and compare the results of the equation of state, nucleon effective mass, and strangeness fraction obtained by adopting the TM1, TMA, and GL parameter sets for nuclear sector and three different choices for the hyperon couplings. We find that the parameter set TM1 favours the onset of hyperons most, while at high densities the GL parameter set leads to the most hyperon-rich matter. For a certain parameter set (e.g. TM1), the most hyperon-rich matter is obtained for the hyperon potential model. The influence of the hyperon couplings on the effective mass of nucleon, is much weaker than that on the nucleon parameter set. The nonstrange mesons dominate essentially the global properties of dense hyperon matter. The hyperon potential model predicts the lowest value of the neutron star maximum mass of about 1.45 Msun to be 0.4-0.5 Msun lower than the prediction by using the other choices for hyperon couplings.
118506081
Three-body force effect on the properties of nuclear matter under the gap and continuous choices within the BHF approach
We have calculated and compared the three-body force effects on the properties of nuclear matter under the gap and continuous choices for the self-consistent auxiliary potential within the Brueckner-Hartree-Fock approach by adopting the Argonne V-18 and the Bonn B two-body potentials plus a microscopic three-body force (TBF). The TBF provides a strong repulsive effect on the equation of state of nuclear matter at high densities for both the gap and continuous choices. The saturation point turns out to be much closer to the empirical value when the continuous choice is adopted. In addition, the dependence of the calculated symmetry energy upon the choice of the self-consistent auxiliary potential is discussed.
15459179
Probing the isospin dependent in-medium nucleon–nucleon cross section by nucleon emissions
The effects of the symmetry potential and the isospin dependent in-medium nucleon-nucleon (NN) cross section on the number of proton(neutron) emissions N-p(N-n) are studied respectively within an isospin-dependent quantum molecular dynamics (IQMD) model. The isospin dependent in-medium NN cross section is found to have a strong influence on Np (Nn) but Np(Nn) is not sensitive to the symmetry potential for the neutron-deficient colliding system at relatively high energies. We propose to make use of the N-p(N-n) as a probe to extract information on the isospin dependent in-medium NN cross section. (C) 2002 Elsevier Science B.V. All rights reserved.
118833038
Transport parameters in neutron stars from in-medium NN cross sections
We present a numerical study of shear viscosity and thermal conductivity of symmetric nuclear matter, pure neutron matter, and beta-stable nuclear matter, in the framework of the Brueckner theory. The calculation of in-medium cross sections and nucleon effective masses is performed with a consistent two- and three-body interaction. The investigation covers a wide baryon density range as needed in the applications to neutron stars. The results for the transport coefficients in beta-stable nuclear matter are used to make preliminary predictions on the damping time scales of nonradial modes in neutron stars.
119110371
Three-body force effect on off-shell mass operator and spectral functions in nuclear matter
Within the framework of the Brueckner theory, the off-shell behaviors of the mass operator $M(k,\omega)=V(k,\omega)+iW(k,\omega)$, i.e., its dependence upon the momentum $k$ and upon the nucleon frequency $\omega$, are investigated by including nuclear three-body force (TBF). The first two terms of the hole-line expansion of the mass operator are taken into account. The TBF effects on their off-shell properties are discussed. A comparison is made between the on-shell and off-shell values of $M_{1}$. The nucleon spectral function and nucleon momentum distribution are also calculated, and the calculation shows that they are hardly affected by the TBF effect at the saturation density. At a high density two times greater than the saturation density, inclusion of the TBF may lead to a visible effect on the spectral function and may enhance the depletion of the hole states.
119275256
Effects of the magnetic field on the spallation reaction implemented by BUU coupled with a phase-space coalescence afterburner
Based on the Boltzmann-Uehling-Uhlenbeck (BUU) transport model coupled with a phase-space coalescence afterburner, the spallation reaction p + 197Au at the incident beam energy Ebeam = 800 MeV/nucleon is studied. We find that the number of test particles per nucleon has minor effects on the neutron-to-proton ratio (n/p) of the produced heavier fragments while it affects much their yields. The external strong magnetic field affects the production of heavier fragments more than the n/p of produced fragments. The n/p of free nucleons is greatly affected by the strong magnetic field, especially for the nucleons with lower energies.
124955332
A New Derivation of Standard Quantum Chromodynamics Evolution Equation
Standard evolution equation including virtual graphs is derived in time ordered perturbative theory. We propose a new cutting rule in deep inelastic scattering processes, which provides a useful tool for discussing the connections among the real and virtual cut diagrams and better understanding of evolution equation.
118982861
Sudakov form factor in effective field theory
We discuss the Sudakov form factor in the framework of the soft-collinear effective theory. The running of the short distance coefficient function from high to low scale gives the summation of Sudakov logarithms to all orders. Our discussions concentrate on the factorization and derivation of the renormalization group equation from the effective theory point of view. The intuitive interpretation of the renormalization group method is discussed. We compared our method with other resummation approaches in the literatures.
119155459
Neutrino decay as a possible interpretation of the MiniBooNE observation with unparticle scenario
In a new measurement on neutrino oscillations, νμ→νe, the MiniBooNE Collaboration observes an excess of electron-like events at low energy and the phenomenon may demand an explanation that obviously is beyond the oscillation picture. We propose that the heavier neutrino, ν2, decaying into a lighter one, ν1, via the transition process νμ→νe+X, where X denotes any light products, could be a natural mechanism. The theoretical model we employ here is the unparticle scenario established by Georgi. We have studied two particular modes $\nu_{\mu}\to\nu_{e}+\mathcal{U}$ and νμ→νe+ν̄e+νe. Unfortunately, the number coming out of the computation is too small to explain the observation. Moreover, our results are consistent with the cosmology constraint on the neutrino life time and the theoretical estimation made by other groups; therefore, we can conclude that even though neutrino decay seems plausible in this case, it indeed cannot be the source of the peak at lower energy observed by the MiniBooNE Collaboration and there should be other mechanisms responsible for the phenomenon.
124490688
THE VIRTUAL EXCHANGE OF PSEUDOSCALAR MESONS IN THE MIT BAG MODEL
In this paper the virtual exchange effect of pseudoscalar mesons in the MIT bag model is discussed and the mass spectrum of hadrons, the magnetic moments and the mean square values of charge radius are calculated. It is pointed out that our model can preserve and improve the static properties of the MIT bag model and provide an explanation for the origin of the meson cloud outside baryons.
124473583
Partonic Structure of the Pomeron in the Modified GLR Equation
The gluon recombination effect in the pomeron is studied by using the modified Gribov–Levin–Ryskin evolution equation. We find that the measured parton distributions in the pomeron can be generated dynamically from a purely gluonic input on assuming a small size for the pomeron.