198 research outputs found
Chiral expansion of the decay width
A chiral field theory of mesons has been applied to study the contribution of
the current quark masses to the decay width at
the next leading order. enhancement has been predicted and there is no
new parameter.Comment: 9 page
1/Nc Countings in Baryons
The power countings for baryon decays and configuration mixings are
determined by means of a non-relativistic quark picture. Such countings are
expected to be robust under changes in the quark masses, and therefore valid as
these become light. It is shown that excited baryons have natural widths of
. These dominant widths are due to the decays that proceed
directly to the ground state baryons, with cascade decays being suppressed to
. Configuration mixings, defined as mixings between states
belonging to different multiplets, are shown to be
sub-leading in an expansion in when they involve the ground
state baryons, while the mixings between excited states can be
.Comment: 19 pages, 1 figure An omission that changes the conclusions on
configuration mixings has been correcte
Nucleon and Delta axial-vector couplings in 1/Nc - Baryon Chiral Perturbation Theory
In this contribution, baryon axial-vector couplings are studied in the
framework of the combined 1/Nc and chiral expansions. This framework is
implemented on the basis of the emergent spin-flavor symmetry in baryons at
large Nc and HBChPT, and linking both expansions (\xi-expansion), where 1/Nc is
taken to be a quantity O(p). The study is carried out including one-loop
contributions, which corresponds to O(\xi^3) for baryon masses and O(\xi^2) for
the axial couplings. An analysis of the Lattice QCD results for the axial
couplings of both N and \Delta is presented.Comment: Presented by A. Calle Cordon at the The 7th International Workshop on
Chiral Dynamics, August 6 -10, 2012, Jefferson Lab, Newport News, Virginia,
US
Radiative Transitions in Heavy Mesons in a Relativistic Quark Model
The radiative decays of , , and other excited heavy mesons are
analyzed in a relativistic quark model for the light degrees of freedom and in
the limit of heavy quark spin-flavor symmetry. The analysis of strong decays
carried out in the corresponding chiral quark model is used to calculate the
strong decays and determine the branching ratios of the radiative decays.
Consistency with the observed branching ratios requires the inclusion of the
heavy quark component of the electromagnetic current and the introduction of an
anomalous magnetic moment for the light quark. It is observed that not only
, but also meson transitions within a heavy quark spin multiplet are
affected by the presence of the heavy quark current.Comment: 9 pages, RevTeX. Submitted to Physical Review
A relativistic chiral quark model for pseudoscalar emission from heavy mesons
The amplitudes for one-pion mediated transitions between heavy meson excited
states are obtained in the framework of the relativistic chiral quark model.
The effective coupling constants to pions and the decay widths of excited heavy
mesons with l<=2 for non-radially excited, and the l=0 radially excited mesons
are presented for both charmed and beauty mesons. We also discuss the allowed
decays of strange excited heavy mesons by emission of a K-meson.Comment: 20 pages, revte
Phenomenological Study of Strong Decays of Heavy Hadrons in Heavy Quark Effective Theory
The application of the tensor formalism of the heavy quark effective theory
(HQET) at leading order to strong decays of heavy hadrons is presented.
Comparisons between experimental and theoretical predictions of ratios of decay
rates for B mesons, D mesons and kaons are given. The application of HQET to
strange mesons presents some encouraging results. The spin-flavor symmetry is
used to predict some decay rates that have not yet been measured.Comment: 10 page
Transport coefficients in Chiral Perturbation Theory
We present recent results on the calculation of transport coefficients for a
pion gas at zero chemical potential in Chiral Perturbation Theory using Linear
Response Theory. More precisely, we show the behavior of DC conductivity and
shear viscosity at low temperatures. To compute transport coefficients, the
standard power counting of ChPT has to be modified. The effects derived from
imposing unitarity are also analyzed. As physical applications in Relativistic
Heavy Ion Collisions, we show the relation of the DC conductivity to
soft-photon production and phenomenological effects related to a nonzero shear
viscosity. In addition, our values for the shear viscosity to entropy ratio
satisfy the KSS bound.Comment: 3 pages, 6 figures, EPJA style. Talk given at the QNP06 conference in
Madrid, and accepted for publication in EPJ
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