Charged pion production in2Ato8AGeVcentralAu+AuCollisions

Momentum spectra of charged pions over nearly full rapidity coverage from target to beam rapidity have been extracted from $0-5\%$ most central $\text{Au}+\text{Au}$ collisions in the beam energy range from $2A$ to $8A\text{GeV}$ by the E895 experiment. Using a thermal parametrization to fit the transverse mass spectra, rapidity density distributions are extracted. The observed spectra are compared with predictions from the RQMD version 2.3 cascade model and also to a thermal model including longitudinal flow. The total $4\pi$ yields of the charged pions are used to infer an initial-state entropy produced in the collisions.