| Charged pions from Ni on Ni collisions between 1 and 2 AGeV (2007) | |||||||||||||
Abstract | |||||||||||||
| . Charged pions from Ni + Ni reactions at 1:05; 1:45 and 1:93 AGeV are measured with the FOP I detector. The mean ß \Sigma multiplicities per mean number of participants increase with beam energy, in accordance with earlier studies of the Ar + KCl and La + La systems. The pion kinetic energy spectra have concave shape and are fitted by the superposition of two Boltzmann distributions with different temperatures. These apparent temperatures depend only weakly on bombarding energy. The pion angular distributions show a forward /backward enhancement at all energies, but not the \Theta = 90 0 enhancement which was observed in case of the Au + Au system. These features also determine the rapidity distributions which are therefore in disagreement with the hypothesis of one thermal source. The importance of the Coulomb interaction and of the pion rescattering by spectator matter in producing these phenomena is discussed. 1 Introduction This paper presents data on the ß \Sigma emissio... | |||||||||||||
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