Isospin breaking in pion and Ke4K_{e4} form factors

Isospin breaking in the $K_{\ell 4}$ form factors induced by the difference between charged and neutral pion masses is discussed within a framework built on suitably subtracted dispersion representations. The $K_{\ell 4}$ form factors are constructed in an iterative way up to two loops in the low-energy expansion by implementing analyticity, crossing, and unitarity due to two-meson intermediate states. Analytical expressions for the phases of the two-loop form factors of the $K^\pm\to\pi^+\pi^- e^\pm \nu_e$ channel are presented, allowing one to connect the difference of form-factor phase shifts measured experimentally (out of the isospin limit) and the difference of $S$- and $P$-wave $\pi\pi$ phase shifts studied theoretically (in the isospin limit). The dependence with respect to the two $S$-wave scattering lengths $a_0^0$ and $a_0^2$ in the isospin limit is worked out in a general way, in contrast to previous analyses based on one-loop chiral perturbation theory. The results on the phases of the $K^\pm\to\pi^+\pi^- e^\pm \nu_e$ form factors obtained by the NA48/2 collaboration at the CERN SPS are reanalysed including isospin-breaking correction to extract values for the scattering lengths $a_0^0$ and $a_0^2$.Comment: 15 pages, 3 figures, prepared for the proceedings of the XIth Confinement and Hadron Spectrum Conference, Saint-Petersburg, Sept. 8-12, 201

Regionalization and Labour Market Rigidities in Developing Countries: A CGE Analysis of UEMOA

In this study, we analyse the impact of the creation of a customs union among UEMOA (Western African Economic and Monetary Union)countries, with a special emphasis on the labour market structure. The implementation of the customs union reform will translate in most of these countries, into a greater openness, even with third party countries. This greater openness raises concerns in these countries as regards its potential impact on welfare, production and employment. In this study, in contrast to many other papers, we relax the assumption of a perfect functioning of the labour market. We consider the presence of a dualism in the labour market and the existence of a minimum wage for the formal workers. We use a multi-country and multi-sectoral computable general equilibrium model (CGE) to assess the impact of the reform. We find that the presence of a minimum nominal wage for the formal workers may significantly reduce the gains stemming from the customs union reform. Our simulation results indicate that the costs induced by this rigidity may exceed 45%, in some cases, in terms of the reduction in the welfare gains obtained without rigidity.Economic integration, Customs union, Labor market, Dualism, Wage rigidity

Trade Policy and Poverty in Benin: a General Equilibrium Analysis

Economic and financial crisis in Benin since 1980s led the government to embark on a process of economic reforms in 1991. These reforms sought to remedy the fiscal and trade imbalances in order to accelerate economic growth. Trade policy reform was given priority. Import bans and quotas were eliminated, import duties abolished and a compensatory tax on commodities sold in the domestic market instituted. This study analyzes the effects of the trade policy reforms using a computable general equilibrium (CGE) model and household survey data. Results show that these reforms are more beneficial to households in urban areas, but contribute to worsening poverty conditions of the most poor in rural areas. If liberalization policies target better strategies aimed at fighting poverty, or at least not deteriorating the situation, they need to be designed in a way that they do not worsen the poverty conditions of the most destitute in society.CGE, trade, poverty, Benin

Chiral Perturbation Theory and Baryon Properties

Theoretical as well as experimental progress has been made in the last decade in describing the properties of baryons. In this review I will mostly report on the theoretical issues. Two non-perturbative methods are privileged frameworks for studying these properties in the low energy domain: chiral perturbation theory, the effective field theory of the Standard Model at energies below 1 GeV and lattice QCD. I will mainly concentrate here on the first one but I will also discuss the complementarity of the two methods. Chiral extrapolations for lattice simulations of some nucleon properties will be investigated. I will then concentrate on processes involving at most two nucleons, describing for example pion-nucleon and pion-deuteron scattering, pion photo- and electroproduction off the nucleon and the deuteron and doubly virtual Compton scattering. Three flavor calculations will also be reviewed.Comment: commissioned article for Prog. Nucl. Part. Phy

Novel analysis of chiral loop effects in the generalized Gerasimov-Drell-Hearn sum rule

We study the chiral loop corrections to the generalized Gerasimov-Drell-Hearn sum rule of the nucleon for finite photon virtuality in the framework of a Lorentz-invariant formulation of baryon chiral perturbation theory. We perform a complete one-loop calculation and obtain significant differences to previously found results based on the heavy baryon approach for the proton and neutron spin-dependent forward Compton amplitudes.Comment: 7 pp, 3 figs, published version, extended discussion, minor revision

Short-distance QCD corrections to K0Kˉ0K^0\bar{K}^0 mixing at next-to-leading order in Left-Right models

Left-Right (LR) models are extensions of the Standard Model where left-right symmetry is restored at high energies, and which are strongly constrained by kaon mixing described in the framework of the $|\Delta S|=2$ effective Hamiltonian. We consider the short-distance QCD corrections to this Hamiltonian both in the Standard Model (SM) and in LR models. The leading logarithms occurring in these short-distance corrections can be resummed within a rigourous Effective Field Theory (EFT) approach integrating out heavy degrees of freedom progressively, or using an approximate simpler method of regions identifying the ranges of loop momentum generating large logarithms in the relevant two-loop diagrams. We compare the two approaches in the SM at next-to-leading order, finding a very good agreement when one scale dominates the problem, but only a fair agreement in the presence of a large logarithm at leading order. We compute the short-distance QCD corrections for LR models at next-to-leading order using the method of regions, and we compare the results with the EFT approach for the $WW'$ box with two charm quarks (together with additional diagrams forming a gauge-invariant combination), where a large logarithm occurs already at leading order. We conclude by providing next-to-leading-order estimates for $cc$, $ct$ and $tt$ boxes in LR models.Comment: Accepted for publication in JHE

Agricultural Trade Liberalization, Productivity Gain and Poverty Alleviation: a General Equilibrium Analysis

Computable General Equilibrium (CGE) models have gained continuously in popularity as an empirical tool for assessing the impact of trade liberalization on agricultural growth, poverty and income distribution. Conventional models ignore however the channels linking technical change in agriculture, trade openness and poverty. This study seeks to incorporate econometric evidence of these linkages into a CGE model to estimate the impact of alternative trade liberalization scenarios on poverty and equity. The analysis uses the Latent Class Stochastic Frontier Model (LCSFM) and the metafrontier function to investigate the influence of trade openness on agricultural technological change. The estimated productivity effects induced from higher levels of trade are combined with a general equilibrium analysis of trade liberalization to evaluate the income and prices changes. These effects are then used to infer the impact on poverty and inequality following the top-down approach. The model is applied to Tunisian data using the social accounting matrix of 2001 and the 2000 household expenditures surveys. Poverty is found to decline under agricultural and full trade liberalization and this decline is much more pronounced when the productivity effects are included.Openness, Agriculture, Productivity, Poverty, CGE modeling

Recent results in chiral nuclear dynamics

Some recent developments in the description of nuclear forces and few-nucleon dynamics derived from chiral effective field theory are reviewed.Comment: invited talk at the International Workshop SCGT 02 "Strong Coupling Gauge Theories and Effective Field Theories", 10-13 December 2002, Nagoya, Japa