Simulation of $Z$ boson $p_T$ spectrum at Tevatron by leading-order event generators

Abstract

We show that the transverse momentum ($p_T$) spectrum of $Z$ boson production measured at Fermilab Tevatron can be well reproduced by leading-order event generators if $Z$ + 1 jet processes are included with a proper solution for the double-count problem and if the parton shower (PS) branch kinematics are defined appropriately. The choice of the PS evolution variable does not definitely determine the low-$p_T$ behavior. Our new event generator employing the limited leading-log (LLL) subtraction and a built-in leading-log PS reproduces the spectrum very well, not only in large $p_T$ regions but also at low $p_T$ down to $p_T$ = 0.

Comments: 13 pages, 4 figures: explanations were added to clarify the discussions. Minor changes for publication