11,350 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.
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
The cranking formula and the spurious behaviour of the mass parameters
We discuss some aspects of the approach of the mass parameters by means of
the simple cranking model. In particular, it is well known that the numerical
application of this formula is often subject to ambiguities or contradictions.
It is found that these problems are induced by the presence of two derivatives
in the formula. To overcome these problems, we state a useful ansatz and we
develop a number of simple arguments which tend to justify the removal of these
terms. As soon as this is done, the formula becomes simpler and easier to
interpret. In this respect, it is shown how the shell effects affect the mass
parameters. A number of numerical tests help us in our conclusions.Comment: version 3 corrigendum of the ansatz of section V, corrigendum of the
legend of Fig3. Submission = text file + 5 figure
Four-quark spectroscopy within the hyperspherical formalism
We present a generalization of the hyperspherical harmonic formalism to study
systems made of quarks and antiquarks of the same flavor. This generalization
is based on the symmetrization of the body wave function with respect to
the symmetric group using the Barnea and Novoselsky algorithm. The formalism is
applied to study four-quark systems by means of a constituent quark model
successful in the description of the two- and three-quark systems. The results
are compared to those obtained by means of variational approaches. Our analysis
shows that four-quark systems with exotic and non-exotic
quantum numbers may be bound independently of the mass of the quark.
and states become attractive only for larger mass of the quarks.Comment: 20 pages, 3 figure
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
Phenomenology of the Heavy Flavored spin 3/2 Baryons in Light Cone QCD
Motivated by the results of the recent experimental discoveries for charm and
bottom baryons, the masses and magnetic moments of the heavy baryons with
containing a single heavy quark are studied within light cone QCD
sum rules method. Our results on the masses of heavy baryons are in good
agreement with predictions of other approaches, as well as with the existing
experimental data.Comment: 12 Pages, 18 Figures and 3 Tables. Based on: arXiv:0807.3481v2
[hep-ph](Nucl.Phys.B808:137-154,2009). To be Published in the Proceeding of
the International Conference on New Trends in High Energy Physics, 27 Sept.-4
Oct. 2008, Yalta, Crimea, Ukrain
Possible eta-mesic 3He states within the finite rank approximation
We extend the method of time delay proposed by Eisenbud and Wigner, to search
for unstable states formed by eta mesons and the 3He nucleus. Using few body
equations to describe eta-3He elastic scattering, we predict resonances and
unstable bound states within different models of the eta-N interaction. The
eta-3He states predicted within this novel approach are in agreement with the
recent claim of the evidence of eta-mesic 3He made by the TAPS collaboration.Comment: 10 pages LaTex, 3 figure
Search for long-lived states in antiprotonic lithium
The spectrum of the (L_i^3 + p-bar + 2e) four-body system was calculated in
an adiabatic approach. The two-electron energies were approximated by a sum of
two single-electron effective charge two-center energies as suggested in [6].
While the structure of the spectrum does not exclude the existence of
long-lived states, their experimental observability is still to be clarified
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