The structure of the nucleon

These lectures give an introduction to the structure of the nucleon as seen with the electromagnetic probe. Particular emphasis is put on the form factors, the strangeness content, Compton scattering and polarizabilities, pion photo- and electroproduction, the spin structure and sum rules. The existing data are compared to predictions obtained from chiral perturbation theory, dispersion theory and effective Lagrangians.Comment: 57 pages LaTex including 15 postscript figures, Proceedings of HUGS at CEBAF 199

Resonance Structure and Polarizability of the nucleon

The main features of the resonance structure of the nucleon are discussed, particular with regard to the helicity dependence of real and virtual photoabsorption. The dependence of the partial cross sections on both the resonance helicity amplitudes and the electromagnetic multipoles is outlined. The general structure of the Compton tensor is reviewed and applied to the special cases of real to real, virtual to real, and virtual to virtual Compton scattering. Recent theoretical developments in dispersion relations are presented, together with a short overview regarding static, dynamical, and generalized polarizabilities of the nucleon as well as the status of the Gerasimov-Drell-Hearn sum rule and related integrals.Comment: 10 pages, 2 figures, Talk given at the symposium on the "Gerasimov-Drell- Hearn Sum Rule and the Nucleon Spin Structure in the Resonance Region" GDH 2002, Genua (Italy), 3.-6. July 200

The Gerasimov-Drell-Hearn sum rule and the single-pion photoproduction multipole E0+ close to threshold

The long-standing discrepancy between the Gerasimov-Drell-Hearn sum rule and the analysis of pion photoproduction multipoles is greatly diminished by use of s-wave multipoles that are in accord with the predictions of chiral perturbation theory and describe the experimental data in the threshold region. The remaining difference may be due to contributions of channels with more pions and/or heavier mesons whose contributions to the sum rule remain to be investigated by a direct measurement of the photoabsorption cross sections.Comment: 9 pages, latex, 1 figure, to appear in Phys. Rev.

Dispersion relation formalism for virtual Compton scattering and the generalized polarizabilities of the nucleon

A dispersion relation formalism for the virtual Compton scattering (VCS) reaction on the proton is presented, which for the first time allows a dispersive evaluation of 4 generalized polarizabilities at a four-momentum transfer $Q^2 \leq$ 0.5 GeV$^2$. The dispersive integrals are calculated using a state-of-the-art pion photo- and electroproduction analysis. The dispersion formalism provides a new tool to analyze VCS experiments above pion threshold, thus increasing the sensitivity to the generalized polarizabilities of the nucleon.Comment: 4 pages, 2 figure

Credit market imperfections, financial market regulation and business cycles in Eastern Europe

Credit market imperfections give rise to boom-bust cycle episodes in emerging markets. In the present paper, we aim to provide a comprehensive analysis for Eastern Europe. We focus on documenting credit market imperfections, asymmetric financing opportunities across sectors, and business cycle fluctuations at the aggregate and sectoral level. The results will be discussed in the policy context of the re-regulation of the financial system. We will propose in an unconventional way to think about the early introduction of the Euro currency. --asymmetric financing opportunities,currency mismatch,sectoral business cycles

Flow of conjunctural information and forecast of euro area economic activity

Euro area GDP and components are nowcast and forecast one quarter ahead. Based on a dataset of 163 series comprising the relevant monthly indicators, simple bridge equations with one explanatory variable are estimated for each. The individual forecasts generated by each equation are then pooled, using six weighting schemes including Bayesian ones. To take into consideration the release calendar of each indicator, six forecasts are compiled independently during the quarter, each based on different information sets: different indicators, different individual equations and finally different weights to aggregate information. The information content of the various blocks of information at different points in time for each GDP component is then discussed. It appears that taking into account the information flow results in significant changes in the weight allocated to each block of information, especially when the first month of hard data becomes available. This conclusion, reached for all the components and most of the weighting scheme, supports and extends the findings of Giannone, Reichlin and Small (2006) and Banbura and Rünstler (2007). An out-of-sample forecast comparison exercise is also carried out for each component and GDP directly. The forecast performance is found to vary widely across components. Two weighting schemes are found to outperform the equal weighting scheme in almost all cases. One-quarter ahead, the direct forecast of GDP is found to outperform the bottom-up approach. However, the nowcast resulting in the lowest forecast errors is derived from the bottom-up approach. JEL Classification: C22, C53, E17forecast pooling, GDP components, Large dataset, weighting scheme

Generalized Polarizabilities in a Constituent Quark Model

We discuss low-energy virtual Compton scattering off the proton within the framework of a nonrelativistic constituent quark model. A simple interpretation of the spin-averaged generalized polarizabilities is given in terms of the induced electric polarization (and magnetization). Explicit predictions for the generalized polarizabilities obtained from a multipole expansion are presented for the Isgur-Karl model and are compared with results of various models.Comment: 10 pages, Latex, 2 figures, uses ws-p8-50x6-00.cls, talk given at NSTAR2001, Workshop on "The Physics of Excited Nucleons," Mainz, Germany, March 7-10, 200

Virtual Compton Scattering at Low Energy and the Generalized Polarizabilities of the Nucleon o

Virtual Compton Scattering on the nucleon: $\gamma^* N \to \gamma N$ is a new and rapidly developing field at low and high energies. This lecture is about the low energy part, i.e. for energies in the $(\gamma p)$ center-of-mass mainly up to the $\Delta(1232)$ resonance region. I review the concept of Generalized Polarizabilities of the Nucleon, and the experiments dedicated to their measurement.Comment: 16 pages, 8 figures. lecture given at the Erice School "Lepton Scattering and the Structure of Hadrons and Nuclei," Erice, 16 - 24 Sept. 2004; to appear in "Progress in Particle and Nuclear Physics