Study of exclusive one-pion and one-eta production using hadron and dielectron channels in pp reactions at kinetic beam energies of 1.25 GeV and 2.2 GeV with HADES

We present measurements of exclusive \(\ensuremath \pi^{+,0}\) and \( \eta\) production in pp reactions at 1.25GeV and 2.2GeV beam kinetic energy in hadron and dielectron channels. In the case of \( \pi^{+}_{}\) and \( \pi^{0}_{}\) , high-statistics invariant-mass and angular distributions are obtained within the HADES acceptance as well as acceptance-corrected distributions, which are compared to a resonance model. The sensitivity of the data to the yield and production angular distribution of \( \Delta\)(1232) and higher-lying baryon resonances is shown, and an improved parameterization is proposed. The extracted cross-sections are of special interest in the case of pp \( \rightarrow\) pp \( \eta\) , since controversial data exist at 2.0GeV; we find \(\ensuremath \sigma=0.142\pm0.022\) mb. Using the dielectron channels, the \( \pi^{0}_{}\) and \( \eta\) Dalitz decay signals are reconstructed with yields fully consistent with the hadronic channels. The electron invariant masses and acceptance-corrected helicity angle distributions are found in good agreement with model predictions.