24,717 research outputs found
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
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
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