Excitation functions of parameters extracted from three-source (net-)proton rapidity distributions in Au-Au and Pb-Pb collisions over an energy range from AGS to RHIC

Experimental results of the rapidity spectra of protons and net-protons (protons minus antiprotons) emitted in gold-gold (Au-Au) and lead-lead (Pb-Pb) collisions, measured by a few collaborations at the alternating gradient synchrotron (AGS), super proton synchrotron (SPS), and relativistic heavy ion collider (RHIC), are described by a three-source distribution. The values of the distribution width sigma(C) and fraction k(C) of the central rapidity region, and the distribution width sigma(F), and rapidity shift Delta(y) of the forward/backward rapidity regions, are then obtained. The excitation function of ac increases generally with increase of the center-of-mass energy per nucleon pair root sNN. The excitation function of sigma(F) shows a saturation at root sNN = 8.8 GeV. The excitation function of k(C) shows a minimum at root sNN = 8.8 GeV and a saturation at root sNN approximate to 17 GeV. The excitation function of Delta y increases linearly with ln (root sNN) in the considered energy range.