No abstract available

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[en] We apply the chiral SU(3) quark mean field model to study the properties of strange hadronic matter at finite temperature. The liquid-gas phase transition is studied as a function of the strangeness fraction. The pressure of the system cannot remain constant during the phase transition, since there are two independent conserved charges (baryon and strangeness number). In a range of temperatures around 15 MeV (precise values depending on the model used) the equation of state exhibits multiple bifurcates. The difference in the strangeness fraction fs between the liquid and gas phases is small when they coexist. The critical temperature of strange matter turns out to be a nontrivial function of the strangeness fraction

[en] The quasielastic (e,e[prime]p) reaction was studied on targets of deuterium, carbon, and iron up to a value of momentum transfer Q2 of 8.1 (GeV/c)2. A nuclear transparency was determined by comparing the data to calculations in the plane-wave impulse approximation. The dependence of the nuclear transparency on Q2 and the mass number A was investigated in a search for the onset of the color transparency phenomenon. We find no evidence for the onset of color transparency within our range of Q2. A fit to the world's nuclear transparency data reflects the energy dependence of the free-proton-nucleon cross section

[en] Measurements of the angular distributions of target and double spin asymmetries for the Delta(1232) in the exclusive channel (polarized-p polarized-e,e-prime p)pi0 obtained at Jefferson Lab in the Q2 range from 0.5 to 1.5 gev2 are presented. Results of the asymmetries are compared with the unitary isobar model, dynamical models, and the effective Lagrangian theory. Sensitivity to the different models was observed, particularly in relation to the description of background terms on which the target asymmetry depends significantly

[en] The Bertsch, nonparametric model of neutron matter is analyzed and strong indications are found that, in the infinite system limit, the ground state is a Fermi liquid with an effective mass, except for a set of measure zero. copyright 1999 The American Physical Society

[en] We report a model-independent partial-wave analysis of polarized dd fusion reactions at low energies. The radial transition amplitudes, designated by the central, spin-orbit, and tensor forces, are determined by fitting angular distributions of the tensor and vector analyzing powers A_XZ(θ), A_ZZ(θ), A_XX-YY(θ), and A_Y(θ), and the unpolarized cross section σ₀(θ). The polarized fusion cross section σ_1,1(θ) is then predicted from these radial transition amplitudes. We stress that this is feasible only when these amplitudes are separated according to the tensor rank of the interaction. This study includes the D-state components of the deuteron, triton, and ³He, and the partial-wave expansion is done up to the d wave for both the entrance and exit channels. Experimental data at E_lab=30, 50, 70, and 90 keV for the d(d,p)t reaction are very well fitted with this method. It is found that the ratio of polarized to unpolarized cross sections is about 86% at 30 keV and goes down to 22% at 90 keV. The implication of the suppression of a polarized dd fusion reaction is discussed in the context of the neutron-lean fusion reactor with polarized D-³He fuel. It turns out that the important range of energy for suppressing the d(d,p)t and d(d,n)³He reactions at the plasma temperature T=60 keV is E_d=80 - 600 keV. More experimental data are needed in this range to make a detailed study of the neutron suppression. copyright 1999 The American Physical Society

[en] The Feynman-Schwinger representation provides a convenient framework for the calculation of nonperturbative propagators. In this paper we first investigate an analytically solvable case, namely the scalar QED in 0+1 dimension. With this toy model we illustrate how the formalism works. The analytic result for the self-energy is compared with the perturbative result. Next, using a χ²φ interaction, we discuss the regularization of various divergences encountered in this formalism. The ultraviolet divergence, which is common in standard perturbative field theory applications, is removed by using a Pauli-Villars regularization. We show that the divergence associated with large values of Feynman-Schwinger parameter s is spurious and it can be avoided by using an imaginary Feynman parameter is. copyright 1999 The American Physical Society

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