Particle production at high energy. II. Accumulative impact and clustering in relativistic heavy-ion collisions

Abstract

Transverse energy dependence ${\mathrm{dE}}_{T}/d\ensuremath{\eta}$ of O+Ag, S+Ag, and S+W collisions at 200 GeV/$c$ are analyzed in a parameter-free phenomenological model of cascade and clustering based on $p$+$p$ and $p$+Ag collisions. The model uses an event generator which explicitly displays the impact parameter dependence of the colliding hadrons and incorporates basic features of multiparticle production in $p$+$p$ collisions. $p$+Ag data at 200 GeV/$c$ are first analyzed with special attention to the time ordering of the cascading many-body processes using the space-time geometry and the impact parameter dependence of the colliding hadrons. We introduce a relaxation time parameter $\ensuremath{\tau},$ the size of a time interval of the overlapping regions of space-time in the center-of-momentum frame of the colliding hadrons. Within a $\ensuremath{\tau}$ interval of relaxation, impacts of all collisions are accumulative. Only after this time has passed are pions allowed to be emitted from excited nuclear matter according to a set of rules for cascade. A value of $\ensuremath{\tau}\ensuremath{\sim}0.1$ fm/$c$ used for $p$+Ag data leads to a description of the gross features of the transverse energy dependence ${\mathrm{dE}}_{T}/d\ensuremath{\eta}$ of O+Ag and S+Ag data of WA80 and S+W data in the forward region of HELIOS.