325 research outputs found
Properties of hyperons in chiral perturbation theory
The development of chiral perturbation theory in hyperon phenomenology has
been troubled due to power-counting subtleties and to a possible slow
convergence. Furthermore, the presence of baryon-resonances, e.g. the
lowest-lying decuplet, complicates the approach, and the inclusion of their
effects may become necessary. Recently, we have shown that a fairly good
convergence is possible using a renormalization prescription of the
loop-divergencies which recovers the power counting, is covariant and
consistent with analyticity. Moreover, we have systematically incorporated the
decuplet resonances taking care of both power-counting and
problems. A model-independent understanding of diferent properties including
the magnetic moments of the baryon-octet, the electromagnetic structure of the
decuplet resonances and the hyperon vector coupling , has been
successfully achieved within this approach. We will briefly review these
developments and stress the important role they play for an accurate
determination of the Cabibbo-Kobayashi-Maskawa matrix element from
hyperon semileptonic decay data.Comment: To appear in HypX Proceeding
The decays within the standard model
We study the reactions within the
minimal standard model. We use isospin symmetry to relate the matrix elements
to the form factors measured in . We argue that these modes are
short distance dominated and can be used for precise determinations of the CKM
parameters and . Depending on the value of the CKM angles we find
branching ratios in the following ranges: ; ; . We also discuss a possible -odd
observable.Comment: 10 pages, LaTeX, 2 Postscript figures. Title and abstract have been
revised to better reflect the content of the paper. This is the final version
as publishe
Magnetic moments of the low-lying , resonances within the framework of the chiral quark model
The magnetic moments of the low-lying spin-parity ,
resonances, like, for example, ,
, as well as their transition magnetic moments, are
calculated using the chiral quark model. The results found are compared with
those obtained from the nonrelativistic quark model and those of unitary chiral
theories, where some of these states are generated through the dynamics of two
hadron coupled channels and their unitarization
Extended nonlocal chiral-quark model for the heavy-light quark systems
In this talk, we report the recent progress on constructing a
phenomenological effective model for the heavy-light quark systems, which
consist of (u,d,s,c,b) quarks, i.e. extended nonlocal chiral-quark model
(ExNLChQM). We compute the heavy-meson weak-decay constants to verify the
validity of the model. From the numerical results, it turns out that (f_D, f_B,
f_{D_s}, f_{B_s})=(207.54,208.13,262.56,262.39) MeV. These values are in
relatively good agreement with experimental data and various theoretical
estimations.Comment: 3 pages, 4 figures, Talk given at the 20th International IUPAP
Conference on Few-Body Problems in Physics (FB20), 20~25 August 2012,
Fukuoka, Japa
Dynamically generated resonances from the vector octet-baryon decuplet interaction
We study the interaction of the octet of vector mesons with the decuplet of
baryons using Lagrangians of the hidden gauge theory for vector interactions.
The unitary amplitudes in coupled channels develop poles that can be associated
with some known baryonic resonances, while there are predictions for new ones
at the energy frontier of the experimental research. The work offers guidelines
on how to search for these resonances
SU(3) breaking corrections to the , , , and decay constants
We report on a first next-to-next-to-leading order calculation of the decay
constants of the () and () mesons using a covariant
formulation of chiral perturbation theory. It is shown that, using the
state-of-the-art lattice QCD results on as input, one can predict
quantitatively the ratios of , , and
taking into account heavy-quark spin-flavor symmetry
breaking effects on the relevant low-energy constants. The predicted relations
between these ratios, and
, and their light-quark mass dependence should be
testable in future lattice QCD simulations, providing a stringent test of our
understanding of heavy quark spin-flavor symmetry, chiral symmetry and their
breaking patterns.Comment: 11 pages, 2 figures, 2 tables; typos corrected, clarifications added,
results remaining unchange
Study of the , and decays
We present an approach to study the decay modes of the into a vector
meson and a tensor meson, taking into account the nature of the ,
, resonances as dynamically generated
states from the vector meson-vector meson interaction. We evaluate four ratios
of partial decay widths in terms of a flavor dependent OZI breaking parameter
and the results obtained compare favorably with experiment. The fit to the data
is possible due to the particular strength and sign of the couplings of the
resonances to pairs of vector mesons given by the theory, thus providing a
nontrivial test for the idea of these tensor states as dynamically generated
from the vector-vector interaction.Comment: published versio
The as a Hybrid
Using the QCD Sum Rule Method, we estimate the mass of the lowest strange
hybrid baryon with . We find the mass is approximately that of
the , whose nature has been a puzzle for many decades. Possible
tests of this result are discussed.Comment: fourteen pages seven figure
Three body systems with strangeness and exotic systems
We report on four 's and three 's, in the 1500 - 1800 MeV
region, as two meson - one baryon S-wave resonances found by solving
the Faddeev equations in the coupled channel approach, which can be associated
to the existing = -1, low lying baryon resonances. On the
other hand we also report on a new, hidden strangeness state, mostly made
of , with mass around 1920 MeV, which we think could be
responsible for the peak seen in the around this
energy. Finally we address a very novel topic in which we show how few body
systems of several mesons can be produced, with their spins aligned up
to J=6, and how these states found theoretically can be associated to several
known mesons with spins J=2,3,4,5,6.Comment: Talk at the 21st European Conference on Few Body Problems in Physics,
Salamanca, Sep. 201
Meson and Baryon resonances
In this talk I review recent advances on the structure of the meson and
baryon resonances which can be dynamically generated from the interaction of
mesons or mesons and baryons. Particular emphasis is put on results involving
vector mesons, which bring new light into the nature of some of the observed
higher mass mesons and baryons and make predictions for new states.Comment: 6 pages, Talk at the PANIC2008 Conferenc
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