Drell-Yan lepton pair production at low invariant masses: transverse-momentum resummation and non-perturbative effects in QCD

A bstract We consider the transverse-momentum ( q T ) distribution of Drell-Yan lepton pairs produced with invariant masses ( M ) from low values up to the Z -boson peak (4 ≤ M ≤ 116 GeV). We present perturbative predictions obtained by consistently combining the resummation of logarithmically enhanced QCD corrections at small q T ( q T ≪ M ) up to next-to-next-to-next-to-next-to-leading logarithmic accuracy with the available fixed-order calculations at next-to-next-to-leading order (i.e. $$\mathcal{O}({\alpha }_{S}^{3})$$ ) valid at large q T . For very low q T ( q T ~ Λ QCD ), non-perturbative (NP) QCD effects become dominant and have been included through a NP form factor with a small number of free-parameters. We compare our results with multiple experimental datasets from hadron colliders, finding excellent agreement between theory and data. By fitting the NP parameters, we achieve a precise extraction of the NP form factor and the so-called Collins-Soper kernel.