53 research outputs found
Covariant solution of the three-quark problem in quantum field theory: the nucleon
We provide details on a recent solution of the nucleon's covariant Faddeev
equation in an explicit three-quark approach. The full Poincare-covariant
structure of the three-quark amplitude is implemented through an orthogonal
basis obtained from a partial-wave decomposition. We employ a rainbow-ladder
gluon exchange kernel which allows for a comparison with meson Bethe-Salpeter
and baryon quark-diquark studies. We describe the construction of the
three-quark amplitude in full detail and compare it to a notation widespread in
recent publications. Finally, we discuss first numerical results for the
nucleon's amplitude.Comment: 10 pages, 4 figures, 4 tables; Contributed to the 19th International
IUPAP Conference on Few-Body Problems in Physics, Bonn, Germany, August 31 -
September 5, 200
Hadron properties from QCD bound-state equations: A status report
Employing an approach based on the Green functions of Landau-gauge QCD, some
selected results from a calculation of meson and baryon properties are
presented. A rainbow-ladder truncation to the quark Dyson-Schwinger equation is
used to arrive at a unified description of mesons and baryons by solving
Bethe-Salpeter and covariant Faddeev equations, respectively.Comment: 6 pages, 4 figures; Plenary talk given at the 5-th Int. Conf. on
Quarks and Nuclear Physics, Beijing, September 21-26,200
The \rho\rho interaction in the hidden gauge formalism and the f_0(1370) and f_2(1270) resonances
We have studied the interaction of vectors mesons within the hidden gauge
formalism and applied it to the particular case of the interaction.
We find a strong attraction in the isospin, spin channels I,S=0,0 and 0,2,
which is enough to bind the system. We also find that the
attraction in the I,S=0,2 channel is much stronger than in the 0,0 case. The
states develop a width when the mass distribution is considered, and
particularly when the decay channel is turned on. Using a
regularization scheme with cut offs of natural size, we obtain results in fair
agreement with the mass and the width of the and meson
states, providing a natural explanation of why the tensor state is more bound
than the scalar and offering a new picture for these states, which would be
dynamically generated from the interaction or, in simpler words,
molecular states.Comment: Version accepted for publicatio
Discussions on Stability of Diquarks
Since the birth of the quark model, the diquark which is composed of two
quarks has been considered as a substantial structure of color anti-triplet.
This is not only a mathematical simplification for dealing with baryons, but
also provides a physical picture where the diquark would behave as a whole
object. It is natural to ask whether such a structure is sufficiently stable
against external disturbance. The mass spectra of the ground states of the
scalar and axial-vector diquarks which are composed of two-light (L-L),
one-light-one-heavy (H-L) and two-heavy quarks (H-H) respectively have been
calculated in terms of the QCD sum rules. We suggest a criterion as the
quantitative standard for the stability of the diquark. It is the gap between
the masses of the diquark and where is the threshold of the
excited states and continuity, namely the larger the gap is, the more stable
the diquark would be. In this work, we calculate the masses of the type H-H to
complete the series of the spectra of the ground state diquarks. However, as
the criterion being taken, we find that all the gaps for the various diquaks
are within a small range, especially the gap for the diquark with two heavy
quarks which is believed to be a stable structure, is slightly smaller than
that for other two types of diquarks, therefore we conclude that because of the
large theoretical uncertainty, we cannot use the numerical results obtained
with the QCD sum rules to assess the stability of diquarks, but need to invoke
other theoretical framework.Comment: 14 pages, 4 figure
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