Simulation of $Z$-boson $p_T$ spectrum at LHC and Tevatron using GR@PPA

Predictions from the GR@PPA event generator concerning the transverse-momentum ($p_T$) spectrum of $Z$ bosons are compared with recent measurements at LHC and Tevatron. The simulation results are in reasonable agreement with the measurements, although marginal discrepancies are observed in high-$p_T$ regions. The principal agreements imply that the leading-order simulation with a primitive parton shower based on the leading-logarithmic approximation still provides a reasonable description of the transverse motion of the hard-interaction system in hadron collisions, without the need to introduce noble techniques to incorporate higher-order corrections.