Chiral expansion of the π0→γγ\pi^0\rightarrow\gamma\gamma decay width

A chiral field theory of mesons has been applied to study the contribution of the current quark masses to the $\pi^0\rightarrow\gamma\gamma$ decay width at the next leading order. $2\%$ enhancement has been predicted and there is no new parameter.Comment: 9 page

1/Nc Countings in Baryons

The $1/N_c$ 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 ${\cal{O}}(N_c^0)$. These dominant widths are due to the decays that proceed directly to the ground state baryons, with cascade decays being suppressed to ${\cal{O}}(1/N_c)$. Configuration mixings, defined as mixings between states belonging to different $O(3)\times SU(2 N_f)$ multiplets, are shown to be sub-leading in an expansion in $1/\sqrt{N_c}$ when they involve the ground state baryons, while the mixings between excited states can be ${\cal{O}}(N_c^0)$.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 $D^*$, $B^*$, 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 $D^*$ 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 $D$, but also $B$ 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