Related papers: Complete experiments in pseudoscalar meson photopr…
We demonstrate that the multipoles associated with the density matrix are truly observable quantities that can be unambiguously determined from intensity moments. Given their correct transformation properties, these multipoles are the…
Near threshold omega meson photoproduction is studied with the CBELSA/TAPS experiment at the ELSA accelerator of Bonn University. Single as well as double polarization observables are measured using either linear or circular polarized…
The amplitude for photoproduction gamma p -> \Upsilon p is calculated in a pQCD k_\perp-factorization approach. The total cross section for diffractive \Upsilon's is compared to recent HERA data. The amplitude is used to predict the cross…
Photoproduction of $\eta$-mesons off deuteron is studied within the Alt-Grassberger-Sandhas formalism for different parameters of $\eta N$ interaction. The calculations revealed peaks in the energy dependence of the total cross-section.
For deuteron photo- and electrodisintegration the selection of complete sets of polarization observables is discussed in detail by applying a recently developed new criterion for the check of completeness of a chosen set of observables. The…
Neutral pion photo- and electroproduction at threshold is analyzed in the framework of dispersion relations. For this purpose, we evaluate the real threshold amplitudes in terms of Born contributions and dispersion integrals determined by…
Kaon photo- and electroproduction off a proton near the production threshold are investigated by utilizing an isobar model. The background amplitude of the model is constructed from Feynman diagrams, whereas the resonance term is calculated…
We discuss how photoproduction and electroproduction processes will provide a precise tool to study nuclear structure in the small-$x$ region in the future Electron-Ion Collider. In particular, we emphasize how exclusive vector meson…
We present a formalism for studying the exclusive production or decay of mesons with any value of the internal orbital angular momentum L. As an application, we discuss the production of meson pairs (involving tensor and pseudotensor…
We develop polarization observables for the processes $\gamma N\to\pi\pi N$ and $\pi N\to\pi\pi N$, using both a helicity and hybrid helicity-transversity basis. Such observables are crucial if processes that produce final states consisting…
The multipole expansion is a key tool in the study of light-matter interactions. All the information about the radiation of and coupling to electromagnetic fields of a given charge-density distribution is condensed into few numbers: The…
Theoretical and experimental studies of high multiplicity events are analyzed. Some interesting phenomena can be revealed at high multiplicities. Preliminary results of project "Thermalization" are reported.
Certain models involving ALPs (axion-like-particles) allow for the coupling of scalars and pseudoscalars to fermions. A derivation of the total rate for production of massive scalars and pseudoscalars by an electron in a monochromatic,…
We summarize the pertinent experimental and theoretical developments in the field of pion photo- and electroproduction in the threshold region. We discuss which experiments and which calculations should be done/performed in the future.
Recursion relations for integrals of amplitudes over the phase space, i.e. for partial wave amplitudes, are introduced. In their simplest form these integrals are proportional to the s-wave amplitudes and represent rigorous lower bounds on…
We discuss coherent and incoherent $\phi$ meson photoproduction off the deuteron at low energy and small momentum transfer with the aim to check whether the recent experimental data need for their interpretation the inclusion of exotic…
We discuss the electroproduction of pseudoscalar ($0^{-+}$) or scalar ($0^{++}$) meson production off the scalar target. The most general formulation of the differential cross section for the $0^{-+}$ or $0^{++}$ meson production process…
Exclusive J/\Psi photo- and electroproduction is studied in the framework of the analytic S-matrix theory. The differential and integrated elastic cross sections are calculated using the Modified Dual Amplitude with Mandelstam Analyticity…
We discuss the procedure of extracting the photoproduction cross section for neutral pseudoscalar mesons off neutrons from deuteron data. The main statement is that the final-state interaction (FSI) corrections for the proton and neutron…
Recent experimental results for the in-medium properties of hadrons obtained with photoproduction of mesons from nuclei are discussed. The experiments were done with the TAPS detector at the tagged photon beam of the MAMI accelerator in…