Scaling Properties of the Mean Multiplicity and Pseudorapidity Density in e – +e + , e ± +p, p( p ¯ )+p, p+A and A+A(B) Collisions
The charged-particle pseudorapidity density ( d N ch /dη ) for p( p¯ )+p, p+A and A+A(B) collisions and the mean multiplicity < N ch > for e – +e + , e ± +p , and p( p¯ )+p collisions are studied for a wide range of beam energies ( √s ). Characteristic scaling patterns are observed for both d N ch /dη and < N ch > , consistent with a thermal particle production mechanism for the bulk of the soft particles created in all of these systems. The scaling patterns found also validate an essential role for quark participants in these collisions. The measured values for d N ch /dη and < N ch > are observed to factorize into contributions that depend on log(√s) and the number of nucleon or quark participant pairs N pp . Here the quantification of these contributions gives expressions that serve to systematize d N ch /dη and < N ch > measurements spanning nearly 4 orders of magnitude in s√ and to predict their values as a function of √s and N pp .