Widths of charged particle pseudorapidity density distributions in high energy and AA collisions

The paper presents a fit to pseudorapidity distributions of final-state charged particles produced in hadron and heavy ion experiments at different center-of-mass energies. Distributions of charged particles measured in , p(d)A, and AA collisions at high energies are presented and good agreement between the fit and the data is found. The basis of the fits is a semi-empirical formula which is obtained from a simple Feynman gas model, namely the two-cylinder gas model. For and AA collisions, the dependence of the width of charged particle pseudorapidity density distributions on logarithmic center-of-mass energy is studied and found to be a linear relationship. Meanwhile, the dependences of the two-cylinder length, single cylinder length, and gap width between the two cylinders on logarithmic center-of-mass energy are found to be linear relationships. As another check and application of the semi-empirical formula, the rapidity distributions of net-protons emitted in AA collisions at high energies are studied. Similar conclusions are obtained.