Meson-baryon interaction in the meson exchange picture

This is the contribution to the proceedings of the MENU 2010 conference. The recent work of Ref. [7] is summarized. Elastic piN scattering and the reaction pi^+ p --> K^+ Sigma^+ are described simultaneously in a unitary coupled-channels approach which respects analyticity. SU(3) flavor symmetry is used to relate the t- and u- channel exchanges that drive the meson-baryon interaction in the different channels. Angular distributions, polarizations, and spin-rotation parameters are compared with available experimental data. The pole structure of the amplitudes is extracted from the analytic continuation.Comment: 4 pages, contribution to the proceedings of the MENU 2010 conference, May 31- June 4, 2010, Williamsburg VA, US

Three-body Unitarity in the Finite Volume

The physical interpretation of lattice QCD simulations, performed in a small volume, requires an extrapolation to the infinite volume. A method is proposed to perform such an extrapolation for three interacting particles at energies above threshold. For this, a recently formulated relativistic $3\to 3$ amplitude based on the isobar formulation is adapted to the finite volume. The guiding principle is two- and three-body unitarity that imposes the imaginary parts of the amplitude in the infinite volume. In turn, these imaginary parts dictate the leading power-law finite-volume effects. It is demonstrated that finite-volume poles arising from the singular interaction, from the external two-body sub-amplitudes, and from the disconnected topology cancel exactly leaving only the genuine three-body eigenvalues. The corresponding quantization condition is derived for the case of three identical scalar-isoscalar particles and its numerical implementation is demonstrated.Comment: 9 pages, 3 figure

The impact of K+Λ\mathbf{K^+\Lambda} photoproduction on the resonance spectrum

The J\"ulich-Bonn coupled-channel framework is extended to $K^+\Lambda$ photoproduction. The spectrum of nucleon and $\Delta$ resonances is extracted from simultaneous fits to several pion-induced reactions in addition to pion, eta and $K^+\Lambda$ photoproduction off the proton. More than 40,000 data points up to a center-of-mass energy of E$\sim$2.3 GeV including recently measured double-polarization observables are analyzed. The influence of the $\gamma p\to K^+\Lambda$ channel on the extracted resonance parameters and the appearance of states not seen in other channels is investigated. The J\"ulich-Bonn model includes effective three-body channels and guarantees unitarity and analyticity, which is a prerequisite for a reliable determination of the resonance spectrum in terms of poles and residues.Comment: 21 pages, 11 figures. Minor modifications, additional information in the appendix. Accepted for publication in Eur. Phys. J.

Correlations of πN\boldsymbol{\pi N} Partial Waves for Multi-Reaction Analyses

In the search for missing baryonic resonances, many analyses include data from a variety of pion- and photon-induced reactions. For elastic $\pi N$ scattering, however, usually the partial waves of the SAID or other groups are fitted, instead of data. We provide the partial-wave covariance matrices needed to perform correlated $\chi^2$ fits, in which the obtained $\chi^2$ equals the actual $\chi^2$ up non-linear and normalization corrections. For any analysis relying on partial waves extracted from elastic pion scattering, this is a prerequisite to assess the significance of resonance signals and to assign any uncertainty on results. The influence of systematic errors is also considered.Comment: 7 pages, 3 figures; Acknowledgements update

Charge fluctuations and electric mass in a hot meson gas

Net-Charge fluctuations in a hadron gas are studied using an effective hadronic interaction. The emphasis of this work is to investigate the corrections of hadronic interactions to the charge fluctuations of a non-interacting resonance gas. Several methods, such as loop, density and virial expansions are employed. The calculations are also extended to SU(3) and some resummation schemes are considered. Although the various corrections are sizable individually, they cancel to a large extent. As a consequence we find that charge fluctuations are rather well described by the free resonance gas.Comment: 32 pages, 18 figure

Dynamical coupled-channel approaches on a momentum lattice

Dynamical coupled-channel approaches are a widely used tool in hadronic physics that allow to analyze different reactions and partial waves in a consistent way. In such approaches the basic interactions are derived within an effective Lagrangian framework and the resulting pseudo-potentials are then unitarized in a coupled-channel scattering equation. We propose a scheme that allows for a solution of the arising integral equation in discretized momentum space for periodic as well as twisted boundary conditions. This permits to study finite size effects as they appear in lattice QCD simulations. The new formalism, at this stage with a restriction to S-waves, is applied to coupled-channel models for the sigma(600), f0(980), and a0(980) mesons, and also for the Lambda(1405) baryon. Lattice spectra are predicted.Comment: 7 pages, 4 figure

Developing modern multifunctional agroforestry systems for sustainable intensification

Agroforestry is a land-use system that integrates trees and shrubs with crops and/or livestock production. It has been identified by the International Assessment of Agricultural Knowledge, Science and Technology for Development (IAASTD, 2008) as a ‘win-win’ approach that balances the production of commodities (food, feed, fuel, fibre, etc.) with non-commodity outputs such as environmental protection and cultural and landscape amenities. This paper will review the potential of agroforestry as part of a multifunctional working landscape in temperate regions, and will consider management and policy implications of widespread adoption of this form of land-use

Pion photoproduction in a dynamical coupled-channel model

Pion photoproduction reactions are investigated in a dynamical coupled-channel approach based on the Juelich pi-N model, which presently includes the hadronic pi-N and eta-N stable channels as well as the pi-Delta, sigma-N and rho-N effective channels. This model has been quite successful in the description of pi-N to pi-N scattering for center-of-mass energies up to 1.9 GeV. The full pion photoproduction amplitude is constructed to satisfy the generalized Ward-Takahashi identity and hence, it is fully gauge invariant. The calculated differential cross sections and photon spin asymmetries up to 1.65 GeV center-of-mass energy for the reactions gamma p to pi+ n, gamma p to pi0 p and gamma n to pi- p are in good agreement with the experimental data.Comment: Invited talk given at 12th International Conference on Meson-Nucleon Physics and the Structure of the Nucleon (MENU2010), Williamsburg, USA, May 31-June 4 201