86 research outputs found
Can the meson cloud explain the nucleon strangeness?
We use the meson cloud model, including the kaon and the contributions,
to estimate the electric and magnetic strange form factors of the nucleon. We
compare our results with the recent measurements of the strange quark
contribution to parity-violating asymmetries in the forward G0 electron-proton
scattering experiment. We conclude that it is not possible to explain the data
using this model.Comment: version accepted for publication in Phys. Rev.
Investigating different structures for the
Using the QCD spectral sum rule approach we investigate different currents
with , which could be associated with the meson. Our
results indicate that, with a four-quark or molecular structure, it is very
difficult to explain the narrow width of the state unless the quarks have a
special color configuration.Comment: 4 pages. Contribution to the proceedings of the 15th International
QCD Conference (QCD10
Testing the molecular nature of D-s0*(2317) and D-0*(2400) in semileptonic B-s and B decays
We study the semileptonic B-s and B decays into the D-s0*(2317) and D-0*(2400) resonances, respectively. With the help of a chiral unitarity model in coupled channels we compute the ratio of the decay widths of both processes. Using current values of the width for the (B) over bar (0) -> D-0*(2400)(+)(v) over bar (l)l(-) we make predictions for the rate of the (B) over bar (0)(s) -> D-s0*(2317)(+)(v) over bar (l)l(-) decay and for the DK invariant mass distribution in the (B) over bar (0)(s) -> DK (v) over bar (l)l(-) decay
QCD sum rule approach for the light scalar mesons as four-quark states
We study the two point-function for the scalar mesons and as diquak-antidiquark states. We also study the decays
of these mesons into , and . We found that the
couplings are consistent with existing experimental data, pointing in favor of
the four-quark structure for the light scalar mesons.Comment: 6 pages, 4 figure
QCD sum rules study of the meson Z^+(4430)
We use QCD sum rules to study the recently observed meson ,
considered as a molecule with . We consider the
contributions of condensates up to dimension eight and work at leading order in
. We get m_Z=(4.40\pm0.10) \GeV in a very good agreement with the
experimental value. We also make predictions for the analogous mesons
and considered as and molecules respectively. For
we predict , which is above the
threshold, indicating that it is probably a very broad state and,
therefore, difficult to be experimentally seen. For we predict
, in agreement with quark model
predictions.Comment: 2 new figures included. version accepted for publication in Phys.
Lett.
Progress in the determination of the cross section
Improving previous calculations, we compute the cross section using QCD sum rules. Our sum rules for the , , and hadronic
matrix elements are constructed by using vaccum-pion correlation functions, and
we work up to twist-4 in the soft-pion limit. Our results suggest that, using
meson exchange models is perfectly acceptable, provided that they include form
factors and that they respect chiral symmetry. After doing a thermal average we
get mb at T=150\MeV.Comment: 22 pages, RevTeX4 including 7 figures in ps file
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