A novel measurement of initial-state gluon radiation in hadron collisions using Drell-Yan events

TL;DR

This paper introduces a new method to measure initial-state gluon radiation in hadron collisions by analyzing the mean transverse momentum of Drell-Yan events, revealing a linear dependence on the invariant mass.

Contribution

It presents a novel approach using the mean Z/γ* transverse momentum as an observable to characterize and model initial-state gluon radiation effects.

Findings

First observation of linear dependence of <p_T^{DY}> on log of invariant mass

Provides a new way to model ISR effects in hadron collisions

Data collected from 9.4 fb^{-1} of Tevatron proton-antiproton collisions

Abstract

A study of initial-state gluon radiation (ISR) in hadron collisions is presented using Drell-Yan (DY) events produced in proton-antiproton collisions by the Tevatron collider at a center-of-mass energy of 1.96 TeV. This paper adopts a novel approach which uses the mean value of the Z/$\gamma^*$ transverse momentum $<p_T^{DY}>$ in DY events as a powerful observable to characterize the effect of ISR. In a data sample corresponding to an integrated luminosity of 9.4 fb$^{-1}$ collected with the CDF Run II detector, $<p_T^{DY}>$ is measured as a function of the Z/$\gamma^*$ invariant mass. It is found that these two observables have a dependence, $<p_T^{DY}> = -8 + 2.2 \ln m_{DY}^2$ [GeV/c], where $m_{DY}$ is the value of the Z/$\gamma^*$ mass measured in units of GeV/$c^2$. This linear dependence is observed for the first time in this analysis. It may be exploited to model the effect of ISR and constrain its impact in other processes.