12,436 research outputs found
D_s (2317) as a four-quark state in QCD sum rules
We perform a QCD sum rule study of the open-charmed as a
four-quark state. Using the diquark-antidiquark picture for the four-quark
state, we consider four possible interpolating fields for , namely,
scalar-scalar, pseudoscalar-pseudoscalar, vector-vector, and
axial-vector--axial-vector types. We test all four currents by constructing
four separate sum rules. The sum rule with the scalar-scalar current gives a
stable value for the mass which qualitatively agrees with the
experimental value, and the result is not sensitive to the continuum threshold.
The vector-vector sum rule also gives a stable result with small sensitivity to
the continuum threshold and the extracted mass is somewhat lower than the
scalar-scalar current value. On the other hand, the two sum rules in the
pseudoscalar and axial-vector channels are found to yield the mass highly
sensitive to the continuum threshold, which implies that a four-quark state
with the combination of pseudoscalar-pseudoscalar or axial-vector--axial-vector
type would be disfavored. These results would indicate that is a
bound state of scalar-diquark and scalar-antidiquark and/or vector-diquark and
vector-antidiquark.Comment: 10 pages, 4 figures, REVTeX, 1 fig. added. to appear in Phys. Rev.
Generalized Density Matrix Revisited: Microscopic Approach to Collective Dynamics in Soft Spherical Nuclei
The generalized density matrix (GDM) method is used to calculate
microscopically the parameters of the collective Hamiltonian. Higher order
anharmonicities are obtained consistently with the lowest order results, the
mean field [Hartree-Fock-Bogoliubov (HFB) equation] and the harmonic potential
[quasiparticle random phase approximation (QRPA)]. The method is applied to
soft spherical nuclei, where the anharmonicities are essential for restoring
the stability of the system, as the harmonic potential becomes small or
negative. The approach is tested in three models of increasing complexity: the
Lipkin model, model with factorizable forces, and the quadrupole plus pairing
model.Comment: submitted to Physical Review C on 08 May, 201
Self-consistent calculations of the electric giant dipole resonances in light and heavy mass nuclei
While bulk properties of stable nuclei are successfully reproduced by
mean-field theories employing effective interactions, the dependence of the
centroid energy of the electric giant dipole resonance on the nucleon number A
is not. This problem is cured by considering many-particle correlations beyond
mean-field theory, which we do within the "Quasiparticle Time Blocking
Approximation". The electric giant dipole resonances in O, Ca,
and Pb are calculated using two new Skyrme interactions.Comment: 4 pages, 4 figure
Temperature dependence of contact resistance of Au-Ti-Pd2Si-n+-Si ohmic contacts
We investigated temperature dependence of contact resistance of an
Au-Ti-Pd2Si ohmic contact to heavily doped n+-Si. The contact resistance
increases with temperature owing to conduction through the metal shunts. In
this case, the limiting process is diffusion input of electrons to the metal
shunts. The proposed mechanism of contact resistance formation seems to realize
also in the case of wide-gap semiconductors with high concentration of surface
states and dislocation density in the contact
More on the Tensor Response of the QCD Vacuum to an External Magnetic Field
In this Letter we discuss a few issues concerning the magnetic susceptibility
of the quark condensate and the Son-Yamamoto (SY) anomaly matching equation. It
is shown that the SY relation in the IR implies a nontrivial interplay between
the kinetic and WZW terms in the chiral Lagrangian. It is also demonstrated
that in a holographic framework an external magnetic field triggers mixing
between scalar and tensor fields. Accounting for this, one may calculate the
magnetic susceptibility of the quark condensate to all orders in the magnetic
field.Comment: 20 pages, 2 figure
Microscopic description of -photoproduction on light nuclei
A microscopic four-body description of near-threshold coherent
photoproduction of the meson on the (3N)-nuclei is given. The
photoproduction cross-section is calculated using the Finite Rank Approximation
(FRA) of the nuclear Hamiltonian. The results indicate that the final state
interaction of the meson with the residual nucleus plays an important
role in the photoproduction process. Sensitivity of the results to the choice
of the T-matrix is investigated. The importance of obeying the
condition of unitarity is demonstrated.Comment: 4 pages, 4 figures; talk given at the International Conference on
Mesons and Light Nuclei '01, Prague, Czech Republic, July 2-6, 2001; to be
published in the Proceedings (AIP press
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