We summarize a new analysis of the distribution $\phi_{ \eta}^{ *}$ of charged leptons produced in decays of $Z$ and $\gamma^{ *}$ bosons in the Collins-Soper-Sterman (CSS) formalism for transverse momentum resummation. By comparing the $\phi_{ \eta}^{ *}$ distribution measured at the Tevatron with the resummed CSS cross section with approximate ${ \cal O}(\alpha_{ s}^{ 2})$ Wilson coefficients, we constrain the magnitude of the nonperturbative Gaussian smearing factor and analyze its uncertainty caused by variations in scale parameters. We find excellent agreement between the $\phi_{ \eta}^{ *}$ data and our theoretical prediction, provided by the \textsc{ ResBos} resummation program. The nonperturbative factor that we obtained can be used to update resummed QCD predictions for precision measurements in inclusive $W$ and $Z$ production and for comparisons to various models of nonperturbative dynamics.
Categories: hep-ph