Theory of the Nucleon Spin-Polarizabilities II

Following up on the plenary talk given by Ulf Mei{\ss}ner, I discuss a generalization of the concept of nucleon spin-polarizabilities in terms of multipole excitation/de-excitation and present an overview of the available theoretical predictions for these elusive but interesting structure parameters of the nucleon.Comment: 4 pages, uses World Scientific style ws-p8-50x6-00.cls; talk given at GDH2000 meeting, Mainz, German

Nucleon Compton Scattering in Chiral Effective Field Theories

Chiral effective field theories have a long history studying the process of Compton scattering on the nucleon. In this contribution I want to focus on the new developments that have occured since the last Chiral Dynamics conference in Mainz 1997. I will focus exclusively on the spin-dependent sector, where most of the recent work has been done.Comment: 10 pages, 2 figures, uses World Scientific style ws-p8-50x6-00.cls; plenary talk given at Chiral Dynamics 2000 meeting, Newport News, V

Chiral Effective Field Theories with explicit Spin 3/2 Degrees of Freedom---A Status Report

Recent developments in calculations of low energy nucleon properties utilizing effective chiral field theories with explicit spin 3/2 matter fields are presented. In particular, the role of Delta resonances in microscopic calculations of the anomalous magnetic moments of the Nucleon is discussed and a comparison to lattice data is performed. Furthermore, the impact of Deltas on the isovector Pauli form factor of the Nucleon and the problems one faces in calculations of the isovector Nucleon-Delta transition form factors are addressed.Comment: 8 pages, Latex, 5 eps figures, uses World Scientific style ws-p8-50x6-00.cls; talk given at NSTAR01, Mainz, German

Chiral Magnetism of the Nucleon

We study the quark mass expansion of the magnetic moments of the nucleon in a chiral effective field theory including nucleons, pions and delta resonances as explicit degrees of freedom. We point out that the usual powercounting applied so far to this problem misses important quark mass structures generated via an intermediate isovector M1 nucleon-delta transition. We propose a modified powercounting and compare the resulting chiral extrapolation function to available (quenched) lattice data. The extrapolation is found to work surprisingly well, given that the lattice data result from rather large quark masses. Our calculation raises the hope that extrapolations of lattice data utilizing chiral effective field theory might be applicable over a wider range in quark masses than previously thought, and we discuss some open questions in this context. Furthermore, we observe that within the current lattice data uncertainties the extrapolations presented here are consistent with the Pade fit ansatz introduced by the Adelaide group a few years ago.Comment: 30 pages, Latex, 7 figure

The electromagnetic Nucleon to Delta transition in Chiral Effective Field Theory

We present a calculation of the three complex form factors parametrizing the nucleon to Delta transition matrix element in the framework of chiral effective field theory with explicit Delta degrees of freedom. The interplay between short and long range physics is discussed and estimates for systematic uncertainties due to higher order effect are given.Comment: Talk given at the 2nd international workshop "Shape of Hadrons", April 27-29, 2006, Athens, Greec

Chiral extrapolations of nucleon properties from lattice QCD

We report on recent work about the study of quark mass dependence of nucleon magnetic moments and axial-vector coupling constant. We examine the feasibility of chiral effective field theory methods for the extrapolation of lattice QCD data obtained at relative large pion masses down to the physical values.Comment: 5pages, LaTeX, 3 figures, uses World Scientific style file; presented at PANIC 02, Osak

Chiral Analysis of the Generalized Form Factors of the Nucleon

We apply the methods of Chiral Perturbation Theory to the analysis of the first moments of the Generalized Parton Distributions in a Nucleon, usually known as generalized form factors. These quantities are currently also under investigation in Lattice QCD analyses of baryon structure, providing simulation results at large quark masses to be extrapolated to the "real world" via Chiral Effective Field Theory. We have performed a leading-one-loop calculation in the covariant framework of Baryon Chiral Perturbation Theory (BChPT), predicting both the momentum and the quark-mass dependence for all the vector and axial (generalized) form factors. In particular we discuss the results for the limit of vanishing four-momentum transfer where the GPD-moments reduce to the well known moments of Parton Distribution Functions (PDFs). We fit our results to available lattice QCD data, extrapolating down to the physical point. We conclude by presenting outstanding results from a combined fit to different GPDs-moments.Comment: 7 pages, 4 figures, Proceedings of Lattice 2007 (July 30 - 4 August 2007, Regensburg, Germany