In the heavy quark limit, a doubly heavy baryon is regarded as composed of a heavy diquark and a light quark. We establish the Bethe-Salpeter (BS) equations for the heavy diquarks and the doubly heavy baryons, respectively, to leading order in a 1/mQ expansion. The BS equations are solved numerically under the covariant instantaneous approximation with the kernels containing scalar confinement and one-gluon-exchange terms. The masses for the heavy diquarks and the doubly heavy baryons are obtained and the non-leptonic decay widths for the doubly heavy baryons emitting a pseudo-scalar meson are calculated within the model.
The vacuum fluctuation (VF) effects on asymmetric nuclear matter are
investigated. Masses of nucleons and mesons are modified in the nuclear medium
by calculating the loop-diagram corrections and the density dependence of
hadron masses is obtained. The relativistic Lagrangian density with the
isovector scalar $\delta$ meson is used to calculate the nuclear equation of
state (EOS) in the framework of the relativistic mean-field (RMF) approach, the
effects of the in-medium hadron masses on the properties of neutron stars are
finally studied. With the inclusion of the VF corrections, the nuclear EOS
becomes softer and the neutron star masses are reduced.Comment: 17 pages, 7 figure
Abstract. The B-meson decay constant fB has been calculated from unquenched lattice QCD in the unphysical region. For extrapolating the lattice data to the physical region, we propose a phenomenological functional form based on the effective chiral perturbation theory for heavy mesons, which respects both the heavy quark symmetry and the chiral symmetry, and the non-relativistic constituent quark model which is valid at large pion masses. The inclusion of pion loop corrections leads to nonanalytic contributions to fB when the pion mass is small. The finite-range regularization technique is employed for the resummation of higher order terms of the chiral expansion. We also take into account the finite volume effects in lattice simulations. The dependence on the parameters and other uncertainties in our model are discussed.
PACS
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