Studies on the production of pions and pion-pion correlations in C+C reactions at the HADES detector at a beam energy of 2 GeV per nucleon

Using the High Acceptance Di-Electron Spectrometer HADES at the heavy-ion synchrotron SIS at the Gesellschaft fuer Schwerionenforschung (GSI) in Darmstadt the production of charged pions and, in an additional step, of pion-pion correlations have been investigated. In this thesis the collision system C+C at an incident kinetic beam energy of 2 GeV per nucleon has been studied. Although the HADES detector has primarily been designed to reconstruct rare decays in the e+e- channel, its wide geometric acceptance and rate capability offer the possibility to study hadron and hadron pair production. In the case of the charged pions, production multiplicities have been determined integrated as well as differentially as a function of rapidity and transverse momentum. The spectra as function of the transverse mass, which were derived from the transverse momentum distributions, have been fitted with the sum of two Maxwell-Boltzmann distributions to acquire the inverse slope parameters. The results of this pion analysis agree within error bars with other experiments. On the basis of the identification of the charged pions, a pion-pion pair analysis has provided for the first time the multiplicity of the K0S meson via the decay channel π+π- in the collision system C+C and an incident kinetic beam energy of 2 GeV per nucleon. Because of its properties the K0S meson decays at a secondary vertex well separated from the primary interaction point. Based upon this decay topology, methods to discriminate against other correlated pion pair sources have been developed. Comparing the K0S multiplicity with the results of the KaoS experiment reveals differences, which, assuming an anisotropic polar emission distribution, are however within errors not significant. Furthermore within this thesis the possible reconstruction of the ρ0 meson via the decay channel ρ0→π+π- in the collision system C+C and an incident kinetic beam energy of 2 GeV per nucleon has been investigated. To summarize, these results demonstrate the principle reconstruction capabilities of HADES for hadrons, especially charged pions (π+,π-), and for pion-pion correlations (K0S→π+π-) in addition and complementary to its leptonic program