Related papers: Generalized Distribution Amplitudes at the $Z$ pol…
A fit of the experimental data to the total cross section of the process $\gamma\gamma->\pi^+\pi^-$ in the energy region from threshold to 2500 MeV has been carried out using dispersion relations with subtractions for the invariant…
We study hard exclusive electroproduction of two pions in the QCD factorization approach at next-to-leading order (NLO) in the strong coupling. The pion pair can be produced both in an isovector and in an isoscalar state. The angular…
Generalized parton distributions (GPDs) have been investigated in the deeply virtual Compton scattering (DVCS) to solve the proton spin puzzle. On the other hand, the generalized distribution amplitudes (GDAs) can be studied in the…
Gravitational form factors of hadrons provide information on mass and pressure distributions in the hadrons, and they have been investigated by generalized parton distributions (GPDs). The GPDs also contain information on internal…
The evolution of the pion distribution amplitude in next-to-leading order is studied for a fixed and a running coupling constant. In both cases, the evolution provides a logarithmic modification in the endpoint region. Assuming a simple…
In this paper we perform an amplitude analysis of essentially all published pion and kaon pair production data from two photon collisions below 1.5 GeV. This includes all the high statistics results from Belle, as well as older data from…
The nonresonant mechanism in the reactions $e^+\,e^-\to \pi^-\,p\,\bar{n}$ and $e^+\,e^-\to \pi^+\,n\,\bar{p}$ is investigated in frame of the one-photon exchange approximation. The description of the hadronic phase space and the invariant…
The production of the three normal neutrinos via $e^-e+$ collision at $Z$-boson peak (neutrino production in a Z-factory) is investigated thoroughly. The differences of $\nu_e$-pair production from $\nu_\mu$-pair and $\nu_\tau$-pair…
The extension of the concept of generalized parton distributions leads to the introduction of baryon to meson transition distribution amplitudes (TDAs), non-diagonal matrix elements of the nonlocal three quark operator between a nucleon and…
Neutral gauge bosons beyond the Standard Model are becoming interesting as possible mediators to explain several experimental anomalies. They have small masses, below one GeV, and are referred to as dark photons, $U$, $A'$ or $Z'$ bosons.…
Hadron tomography can be investigated by three-dimensional structure functions such as generalized parton distributions (GPDs), transverse-momentum-dependent parton distributions, and generalized distribution amplitudes (GDAs). Here, we…
Photoproduction of $\pi^{0}\pi^{0}$ and $\pi^{0}\pi^{\pm}$ pairs from nuclei has been measured over a wide mass range ($^2$H, $^{7}$Li, $^{12}$C, $^{40}$Ca, and $^{\rm nat}$Pb) for photon energies from threshold to 600 MeV. The experiments…
Recent experimental pion polarizability data are reviewed and analyzed. Data on the radiative \pi^+ meson photoproduction on the proton at MAMI has been used to determine the difference of the electric and magnetic dipole polarizabilities…
The cross sections for the production of two-pions in ultraperipheral ultrarelativistic heavy ion collisions, calculated in the impact parameter Equivalent Photon Approximation (EPA), are presented. Differential distributions in impact…
We compute the matrix elements for pion emission from the nucleon induced by twist-two light-cone operators in the kinematics where the pion is close to threshold. It is shown that the results of heavy baryon ChPT are in agreement with the…
Regge-pole based descriptions of pion-electroproduction on nucleons have given a very good description of the longitudinal components of the cross sections. However, these very same models grossly underestimate the transverse components. A…
We report a measurement of the exclusive production of pairs of charged pions in proton-proton collisions, dominated by the process $pp \rightarrow p^{(*)} \pi^{+}\pi^{-} p^{(*)}$, where $\rm p^{(*)}$ stands for a diffractively dissociated…
A study of Bose-Einstein correlations in pairs of identically charged pions produced in e+e- annihilations at the Z0 peak has been performed for the first time assuming a non-static emitting source. The results are based on the high…
We present a high-statistics measurement of differential cross sections and the total cross section for the process gamma gamma -> pi^0 pi^0 in the kinematic range 0.6 GeV <= W <= 4.0 GeV and |cos theta*| <= 0.8, where W and theta* are the…
A new partial wave analysis of pion photoproduction has been obtained in the framework of fixed-t dispersion relations valid form threshold up to 500 MeV. It is based on new Mainz data for \pi^{0} and \pi^{+} production off the proton and…