Measurement of charged pions in 12 C + 12 C collisions at 1 A GeV and 2 A GeV with HADES

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, which are related to neutral pions representing a dominant contribution to the dielectron yield. We have performed the first large-angular range measurement of the distribution of π mesons for the C + C collision system covering a fairly large rapidity interval. The pion yields, transverse-mass and angular distributions are compared with calculations done within a transport model, as well as with existing data from other experiments. The anisotropy of pion production is systematically analyzed. PACS. 25.75.-q heavy-ion collisions 25.75.Dw charged pion spectra 2 G. Agakishiev et al.: Measurement of charged pions in C + C collisions at 1A GeV and 2A GeV with HADES