210 research outputs found
Tetraquark bound states in a constituent quark model and the nature of the a_0(980) and f_0(980)
In this work we study tetraquark bound states in the framework of the
constituent quark model of Ref. [2], which has been used for the description of
non-strange two- and three-baryon systems and later on applied to the hadron
spectra.Comment: Contribution to the MESON 2002 Workshop. Krakow 24-28 May 200
Extensions of the auxiliary field method to solve Schr\"{o}dinger equations
It has recently been shown that the auxiliary field method is an interesting
tool to compute approximate analytical solutions of the Schr\"{o}dinger
equation. This technique can generate the spectrum associated with an arbitrary
potential starting from the analytically known spectrum of a particular
potential . In the present work, general important properties of the
auxiliary field method are proved, such as scaling laws and independence of the
results on the choice of . The method is extended in order to find
accurate analytical energy formulae for radial potentials of the form , and several explicit examples are studied. Connections existing
between the perturbation theory and the auxiliary field method are also
discussed
Tetraquarks in a chiral constituent quark model
We analyze the possibility of heavy-light tetraquark bound states by means of
a chiral constituent quark model. The study is done in a variational approach.
Special attention is paid to the contribution given by the different terms of
the interacting potential and also to the role played by the different color
channels. We find a stable state for both and
configurations. Possible decay modes of these structures are
analyzed.Comment: 13 pages, no figures. Accepted for publication in European Journal of
Physics
Isospin Mass Splittings of Baryons in Potential Models
We discuss the isospin-breaking mass differences among baryons, with particular attention in the charm sector to the , models cannot accommodate the trend of the available data on charmed baryons. More precise measurements would offer the possibility of testing how well potential models describe the non-perturbative limit of QCD
Isospin Splittings of Baryons
We discuss the isospin-breaking mass differences among baryons, with
particular attention in the charm sector to the ,
, and splittings. Simple potential
models cannot accommodate the trend of the available data on charm baryons.
More precise measurements would offer the possibility of testing how well
potential models describe the non-perturbative limit of QCD.Comment: 4 pages, aipproc.sty, Proceeding of Hadron 9
Baryons Electromagnetic Mass Splittings in Potential Models
We study electromagnetic mass splittings of charmed baryons. We point out
discrepancies among theoretical predictions in non-relativistic potential
models. None of them seems supported by experimental data. A new calculation is
presented.Comment: 4 pages, Proc. of ISS97 Tashkent 6-13 Oct. 9
Modified Newton's law, braneworlds, and the gravitational quantum well
Most of the theories involving extra dimensions assume that only the
gravitational interaction can propagate in them. In such approaches, called
brane world models, the effective, 4-dimensional, Newton's law is modified at
short as well as at large distances. Usually, the deformation of Newton's law
at large distances is parametrized by a Yukawa potential, which arises mainly
from theories with compactified extra dimensions. In many other models however,
the extra dimensions are infinite. These approaches lead to a large distance
power-law deformation of the gravitational newtonian potential , namely
, which is less studied in the literature. We
investigate here the dynamics of a particle in a gravitational quantum well
with such a power-law deformation. The effects of the deformation on the energy
spectrum are discussed. We also compare our modified spectrum to the results
obtained with the GRANIT experiment, where the effects of the Earth's
gravitational field on quantum states of ultra cold neutrons moving above a
mirror are studied. This comparison leads to upper bounds on and .Comment: 11 pages, 1 figur
Doubly heavy quark baryon spectroscopy and semileptonic decay
Working in the framework of a nonrelativistic quark model we evaluate the
spectra and semileptonic decay widths for the ground state of doubly heavy
and baryons. We solve the three-body problem using a variational
ansatz made possible by the constraints imposed by heavy quark spin symmetry.
In order to check the dependence of our resultson the inter-quark interaction
we have used five different quarkquark potentials which include Coulomb and
hyperfine terms coming fromone-gluon exchange, plus a confining term. Our
results for the spectra are in good agreement with a previous calculation done
using a Faddeev approach. For the semileptonic decay our results for the total
decay widths are in a good agreement with the ones obtained within a
relativistic quark model in the quark-diquark approximation.Comment: Talk given at the IVth International Conference on Quarks an Nuclear
Physics (QNP06), Madrid, June 5th-10th 200
Confinement interaction in nonlinear generalizations of the Wick-Cutkosky model
We consider nonlinear-mediating-field generalizations of the Wick-Cutkosky
model. Using an iterative approach and eliminating the mediating field by means
of the covariant Green function we arrive at a Lagrangian density containing
many-point time-nonlocal interaction terms. In low-order approximations of
theory we obtain the usual two-current interaction as well as
a three-current interaction of a confining type. The same result is obtained
without approximation for a version of the dipole model. The transition to the
Hamiltonian formalism and subsequent canonical quantization is performed with
time non-locality taken into account approximately.
A relativistic three-particle wave equation is derived variationally by using
a three-particle Fock space trial state. The non-relativistic limit of this
equation is obtained and its properties are analyzed and discussed.Comment: 15 pages, 1 figure, LaTe
Study of the semileptonic decay \Lambda_b^0 \to \Lambda_c^+ l^- \bar{\nu}_l
Within the framework of a nonrelativistic quark model we evaluate the six
form factors associated to the \Lambda_b^0 \to \Lambda_c^+ l^- \bar{\nu}_l
semileptonic decay. The baryon wave functions were evaluated using a
variational approach applied to a family of trial functions constrained by
Heavy Quark Symmetry (HQS). We use a spectator model with only one-body current
operators. For these operators we keep up to first order terms on the internal
(small) heavy quark momentum, but all orders on the transferred (large)
momentum. Our result for the partially integrated decay width is in good
agreement with lattice calculations. Comparison of our total decay width to
experiment allows us to extract the V_{cb} Cabbibo-Kobayashi-Maskawa matrix
element for which we obtain a value of |V_{cb}|=0.047\pm 0.005 in agreement
with a recent determination by the DELPHI Collaboration. Furthermore, we obtain
the universal Isgur-Wise function with a slope parameter \rho^2=0.98 in
agreement with lattice results.Comment: 4 pages, 3 figures. Presented at 6th International Conference on
Hyperons, Charm and Beauty Hadrons (BEACH 2004), Chicago, Illinois, 27 Jun -
3 Jul 200
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