Role of the nonperturbative input in QCD resummed Drell-Yan QT distributions -: art. no. 114011

We analyze the role of the nonperturbative input in the Collins-Soper-Sterman (CSS) b-space QCD resummation formalism for Drell-Yan transverse momentum (Q(T)) distributions, and investigate the predictive power of the CSS formalism. We find that the predictive power of the CSS formalism has a strong dependence on the collision energy rootS in addition to its well-known Q(2) dependence, and the rootS dependence improves the predictive power at collider energies. We show that a reliable extrapolation from perturbatively resummed b-space distributions to the nonperturbative large b region is necessary to ensure the correct Q(T) distributions. By adding power corrections to the renormalization group equations in the CSS formalism, we derive a new extrapolation formalism. We demonstrate that at collider energies the CSS resummation formalism plus our extrapolation has an excellent predictive power for W and Z production at all transverse momenta Q(T)less than or equal toQ. We also show that the b-space resummed Q(T) distributions provide a good description of Drell-Yan data at fixed target energies.