Rapidity dependence of charged pion production at relativistic energies using Tsallis statistics

Transverse momentum distributions of charged pions produced in Au+Au collisions at 62.4GeV, 130GeV, 200GeV, Cu+Cu and d+Au collisions at 200GeV, p+p collisions at 62.4 and 200GeV and Pb+Pb collisions at 17.3GeV are studied using the Tsallis distribution as a parametrization. The non-extensivity parameter and Tsallis volume increase with energy, while the Tsallis temperature shows a decrease at higher energies. Using BRAHMS $ p_T$ spectra obtained in Au+Au collisions at 62.4GeV and 200GeV, Tsallis fit parameters are obtained on a very wide rapidity range. Results are compared with p+p and Cu+Cu data and changes of Tsallis parameters with rapidity and energy are investigated. We found that non-extensivity parameter q shows a decrease from midrapidity to forward rapidities for all the studied systems. Tsallis volume, V , increases with the system size from p+p, Cu+Cu to Au+Au, both in central rapidity region and at forward rapidities. The values of temperatures increase with rapidity, but the $ T/\cosh(y)$ ratio is constant as a function of rapidity