6,222 research outputs found
On the momentum-dependence of -nuclear potentials
The momentum dependent -nucleus optical potentials are obtained based
on the relativistic mean-field theory. By considering the quarks coordinates of
meson, we introduced a momentum-dependent "form factor" to modify the
coupling vertexes. The parameters in the form factors are determined by fitting
the experimental -nucleus scattering data. It is found that the real
part of the optical potentials decrease with increasing momenta, however
the imaginary potentials increase at first with increasing momenta up to
MeV and then decrease. By comparing the calculated mean
free paths with those from / scattering data, we suggested that the
real potential depth is MeV, and the imaginary potential parameter
is MeV.Comment: 9 pages, 4 figure
Do ESOPs enhance firm performance? Evidence from China's reform experiment
China introduced employee stock ownership plans (ESOPs) in 1992 purely as an employee incentive scheme. The government initiated the policy experiment on ESOPs as part of China's reform of its state-owned enterprises, and it was abruptly terminated 2. years after initiation. This policy experiment resulted in an exogenous sample of ESOPs that allows us to provide the first evidence from Chinese firms on the performance-ESOP relation. After examining a variety of performance measures, including ROA, ROE, Tobin's q, and productivity, we find little difference in performance between ESOP firms and non-ESOP firms. © 2010 Elsevier B.V.postprin
In-medium Properties of as a KN structure in Relativistic Mean Field Theory
The properties of nuclear matter are discussed with the relativistic
mean-field theory (RMF).Then, we use two models in studying the in-medium
properties of : one is the point-like in the usual RMF and
the other is a KN structure for the pentaquark. It is found that the
in-medium properties of are dramatically modified by its internal
structure. The effective mass of in medium is, at normal nuclear
density, about 1030 MeV in the point-like model, while it is about 1120 MeV in
the model of KN pentaquark. The nuclear potential depth of in
the KN model is approximately -37.5 MeV, much shallower than -90 MeV in
the usual point-like RMF model.Comment: 8 pages, 5 figure
The properties of kaonic nuclei in relativistic mean-field theory
The static properties of some possible light and moderate kaonic nuclei, from
C to Ti, are studied in the relativistic mean-field theory. The 1s and 1p state
binding energies of are in the range of MeV and
MeV, respectively. The binding energies of 1p states increase monotonically
with the nucleon number A. The upper limit of the widths are about
MeV for the 1s states, and about MeV for the 1p states. The lower
limit of the widths are about MeV for the 1s states, and
MeV for the 1p states. If MeV, the discrete bound states
should be identified in experiment. The shrinkage effect is found in the
possible kaonic nuclei. The interior nuclear density increases obviously, the
densest center density is about .Comment: 9 pages, 2 tables and 1 figure, widths are considered, changes a lo
Thermodynamics with density and temperature dependent particle masses and properties of bulk strange quark matter and strangelets
Thermodynamic formulas for investigating systems with density and/or
temperature dependent particle masses are generally derived from the
fundamental derivation equality of thermodynamics. Various problems in the
previous treatments are discussed and modified. Properties of strange quark
matter in bulk and strangelets at both zero and finite temperature are then
calculated based on the new thermodynamic formulas with a new quark mass
scaling, which indicates that low mass strangelets near beta equilibrium are
multi-quark states with an anti-strange quark, such as the pentaquark
(u^2d^2\bar{s}) for baryon nmber 1 and the octaquark (u^4d^3\bar{s}) for
dibaryon etc.Comment: 14 pages, 12 figures, Revtex4 styl
-meson in nuclear matter
The -nucleon (N) interactions are deduced from the heavy baryon
chiral perturbation theory up to the next-to-leading-order terms. Combining the
relativistic mean-field theory for nucleon system, we have studied the
in-medium properties of -meson. We find that all the elastic scattering
N interactions come from the next-to-leading-order terms. The N
sigma term is found to be about 280130 MeV. The off-shell terms are also
important to the in-medium properties of -meson. On application of the
latest determination of the N scattering length, the ratio of
-meson effective mass to its vacuum value is near , while
the optical potential is about MeV, at the normal nuclear density.Comment: 8 pages, 3 figures, to appear in PRC, many modification
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