QCD factorized Drell-Yan cross section at large transverse momentum

We derive a new factorization formula in perturbative quantum chromodynamics for the Drell-Yan massive lepton-pair cross section as a function of the transverse momentum Q(T) of the pair. When Q(T) is much larger than the pair's invariant mass Q, this factorization formula systematically resums the logarithmic contributions of the type alpha(s)(m)ln(m)(Q(T)(2)/Q(2)) to all orders in the strong coupling alpha(s). When Q(T)similar toQ, our formula yields the same Drell-Yan cross section as conventional fixed order QCD perturbation theory. We show that resummation is important when the collision energy rootS is large enough and Q(T) much greater than Q, and we argue that perturbative expansions are more stable and reliable in terms of the modified factorization formula.