86 research outputs found
Use of the double dispersion relation in QCD sum rules with external fields
In QCD sum rules with external fields, the double dispersion relation is
often used to represent the correlation function. In this work, we point out
that the double spectral density, when it is determined by successive
applications of the Borel transformation, contains the spurious terms which
should be kept in the subtraction terms in the double dispersion relation. They
are zero under the Borel transformation but, if the dispersion integral is
restricted with QCD duality, they contribute to the continuum. For the simple
case with zero external momentum, it is shown that subtracting out the spurious
terms is equivalent to the QCD sum rules represented by the single dispersion
relation.Comment: 10 pages, slightly revised, accepted for publication in Progress of
Theoretical Physic
Possible signatures for tetraquarks from the decays of ,
Based on the recent proposal for the tetraquarks with the mixing scheme, we
investigate fall-apart decays of into two lowest-lying
mesons. This mixing scheme suggests that and are the
tetraquarks with the mixtures of two spin configurations of diquark and
antidiquark. Due to the relative sign differences in the mixtures, the
couplings of fall-apart decays into two mesons are strongly enhanced for
but suppressed for . We report that this expectation is
supported by their experimental decays. In particular, the ratios of the
associated partial decay widths, which depend on some kinematical factors and
the couplings, are found to be around , , which seems to agree with the experimental ratios reasonably well.
This agreement can be interpreted as the tetraquark signatures for .Comment: 6 pages, no figures, more references are added, the version to be
published in EPJ
Flavor structure of pentaquark baryons in quark model
The flavor SU(3) group structure of pentaquark baryons which form ,
, , , , and multiplets is
investigated in quark model. The flavor wave functions of all the pentaquark
baryons are constructed in SU(3) quark model and their Yukawa interactions with
meson octet are obtained in general and in the special case of the
octet-antidecuplet ideal mixing with the OZI rule. The mass sum rules of
pentaquark baryons are also discussed.Comment: 8 pages, talk presented at International Workshop PENTAQUARK04 at
SPring-8, Japan, July 20-23, 200
Scalar kappa meson in K* photoproduction
We propose that the scalar meson may play an important role in
photoproduction. In the reactions of and
, we consider the production mechanisms including
-channel , , exchanges, s-channel , diagrams,
and -channel , , diagrams within the tree level
approximation, and find that the -meson exchange may contribute
significantly to photoproduction, while it is rather supplementary
in photoproduction. We demonstrate how the observables of
photoproduction can be used to constrain the meson properties. In
particular, the parity asymmetry can separate the meson contribution
in photoproduction.Comment: 9 pages, 4 figures, REVTe
Couplings between pion and charmed mesons
We compute the couplings ,,,
using QCD sum rules. These couplings are important inputs in the meson exchange
model calculations used to estimate the amount of absorption due to
pions and rho mesons in heavy ion collisions. Our sum rules are constructed at
the first order in the pion momentum , which give the couplings that are
not trivially related to the soft-pion theorem. Our calculated couplings, which
somewhat depend upon the values of the heavy meson decay constants, are
, , and .Comment: 16 pages including 4 postscript figures. To be published in European
Physical Journal
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