A modern view of wide-angle exclusive scattering

The basic theoretical ideas of the handbag mechanism for wide-angle exclusive scattering reactions are discussed and, with regard to the present experimental program carried out at JLab, its application to Compton scattering is reviewed in some detail. Results for other wide-angle reactions such as two-photon annihilations into pairs of hadrons or virtual Compton scattering are presented as well.Comment: 10 pages, 6 figures (using LATEX with ws-procs9x6.cls), talk presented at the Nstar2002 workshop on the physics of excited nucleons, Pittsburgh, October 200

GPDs, form factors and Compton scattering

The basic theoretical ideas of the handbag factorization and its application to wide-angle scattering reactions are reviewed. With regard to the present experimental program carried out at JLab, wide-angle Compton scattering is discussed in some detail.Comment: 11 pages, 5 figures (using LATEX with ws-procs9x6.cls), talk presented at the workshop on Exclusive Processes, Jefferson Lab, Newport News, May 200

The gluon contents of the eta and eta' mesons

It is reported on a leading-twist analysis of the eta - photon and eta' - photon transition form factors. The analysis allows for an estimate of the lowest Gegenbauer coefficients of the quark and gluon distribution amplitudes.Comment: 5 pages, 5 figures (using LATEX with aipproc), talk presented at the X. International Conference on Hadron Spectroscopy Aschaffenburg, September 200

Rate optimal estimation of quadratic functionals in inverse problems with partially unknown operator and application to testing problems

We consider the estimation of quadratic functionals in a Gaussian sequence model where the eigenvalues are supposed to be unknown and accessible through noisy observations only. Imposing smoothness assumptions both on the signal and the sequence of eigenvalues, we develop a minimax theory for this problem. We propose a truncated series estimator and show that it attains the optimal rate of convergence if the truncation parameter is chosen appropriately. Consequences for testing problems in inverse problems are equally discussed: in particular, the minimax rates of testing for signal detection and goodness-of-fit testing are derived.Comment: Corrected some typo