On transverse momentum spectra of negative pions in 12C+181Ta collisions at 4.2A GeV/c

We studied the dependences of the experimental transverse momentum spectra of the negative pions, produced in minimum bias 12 C +181 Ta collisions at a momentum of 4.2 GeV/c per nucleon, on the collision centrality and the pion rapidity range. To examine quantitatively, the change in the shape of the pt spectra of π- mesons with the change of collision centrality and the pion rapidity range, all the extracted pt spectra were fitted by the four different functions commonly used for describing the hadron spectra. The extracted values of the spectral temperatures T1 and T2 were consistently larger for the pt spectra of π- mesons coming from midrapidity range as compared to those of the negative pions generated in the target and projectile fragmentation regions. The spectral temperatures of the negative pions coming from projectile fragmentation region proved to be larger than the respective temperatures of the negative pions coming from target fragmentation region. The extracted spectral temperatures T1 and T2 of the pt spectra of π- mesons were compatible within the uncertainties for the peripheral, semicentral and central 12 C +181 Ta collision events, selected using the number of participant protons. It was observed that Hagedorn and Boltzmann functions are more appropriate for describing the transverse momentum spectra of the negative pions as contrasted to Simple Exponential and Gaussian functions.