Measurements of the transverse momenta (${\mathit{p}}_{\mathit{T}}$) of medium and heavy mass projectile fragments for a range of projectile nuclei ${(}^{40}$Ar, ${}_{}{}^{93}{}_{}{}^{}\mathrm{Nb}$, ${}_{}{}^{139}{}_{}{}^{}\mathrm{La}$, ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$) have been carried out. It is found that the width of the transverse momentum distributions increases more rapidly with projectile and fragment mass than predicted by models based on nucleon momenta in the projectile nuclei. The distributions can be fit by including an additional transverse momentum, ${\mathit{p}}_{\mathit{B}}$ (for Bounce). The extracted values of ${\mathit{p}}_{\mathit{B}}$/${\mathit{A}}_{\mathit{F}}$ increase with decreasing ${\mathit{A}}_{\mathit{F}}$, and extrapolations to small ${\mathit{A}}_{\mathit{F}}$ appear to be consistent with the mean values of reaction-plane-projected ${\mathit{p}}_{\mathit{T}}$ per nucleon for light particle (e.g., nucleon) ‘‘bounce-off.’’

DOI:https://doi.org/10.1103/PhysRevC.50.R525