We present the results of a study of charged pion production in C + C collisions at incident beam energies of 1A GeV and 2A GeV using the HADES spectrometer at GSI. The main emphasis of the HADES program is on the dielectron signal from the early phase of the collision. Here, however, we discuss the data with respect to the emission of charged hadrons, specifically the production of π mesons, w...

Within the one-pion exchange model we calculate the near-threshold η ′ production from pp collisions including the final state interaction between the protons. Since the description of the data is quite well we conclude that η, ρ or ω exchange currents either play no role or cancel each other to a large extent in this reaction. Recently the COSY-11 [1] and SPES III [2] Collaborations have measu...

We present an analysis of hadroproduction $J/\psi$ and $\psi(2S)$ at fixed-target energies in the framework non-relativistic QCD (NRQCD). Using both pion- proton-induced data, a new determination color-octet long-distance matrix elements (LDMEs) is obtained. Compared with previous results, contributions from $q \bar{q}$ processes are significantly enhanced, especially lower energies. A good agr...

We consider the production of muon pairs from the scattering of pions on longitudinally polarized protons. We calculate the cross section and the single spin asymmetry for this process, taking into account pion bound state effects. We work in the kinematic region where the photon has a large longitudinal momentum fraction, which allows us to treat the bound state problem perturbatively. Our pre...