Abstract
The formalism for uniform description of Drell-Yan transverse-momentum spectrum is presented in a framework of High-Energy Factorization, which smoothly interpolates between Collins-Soper-Sterman formalism at $|{\bf q}_T|\ll Q$ and usual Collinear Parton Model at $|{\bf q}_T|\sim Q\ll \sqrt{S}$. The new formula for deriving Unintegrated Parton Distribution Functions(UPDFs) from collinear ones is introduced, which leads to excellent description of the shape of $Z$-boson $|{\bf q}_T|$-spectrum at high energies up to $|{\bf q}_T|/\sqrt{S}\simeq 0.02$. Description of normalized $|{\bf q}_T|$-distributions at low energies is achieved via the fit of non-perturbative parameters of quark UPDFs. Reasonable description of angular distributions of leptons in the dilepton center-of-mass frame is also obtained with new UPDFs.
Highlights
The transverse-momentum distribution of Drell-Yan (DY) lepton pairs with large invariant mass Q ≫ ΛQCD, produced in hadronic collisions, continues to attract a lot of attention from theorists and experimentalists alike
Our parton Reggeization approach (PRA) is a version of high-energy factorization (HEF), based on the modified multi-Regge kinematics (MMRK) approximation for QCD scattering amplitudes. This approximation is accurate both in the collinear limit, which drives the transverse-momentum dependent (TMD)-factorization and in the high-energy limit s ≫ ð−ˆtÞ ∼ q2T ∼ Q2 which is important for Balitsky-Fadin-Kuraev-Lipatov (BFKL) [18,19,20] resummation of ln s=ð−ˆtÞ-enhanced effects. This approximation allows us to derive the factorization formula for Drell-Yan cross section, which is equivalent to the perturbative Collins-Soper-Sterman (CSS) formalism [21] for jqTj ≪ Q and accuracy of which at jqTj ∼ Q is expecpteffidffiffi to increapseffiffiffipowerlike with decreasing values of jqTj= S and Q= S
II we introduce the MMRK approximation and derive factorization formula of PRA for the DY process; in the
Summary
The transverse-momentum (qT) distribution of Drell-Yan (DY) lepton pairs with large invariant mass Q ≫ ΛQCD, produced in hadronic collisions, continues to attract a lot of attention from theorists and experimentalists alike. Our parton Reggeization approach (PRA) is a version of HEF, based on the modified multi-Regge kinematics (MMRK) approximation for QCD scattering amplitudes This approximation is accurate both in the collinear limit, which drives the TMD-factorization and in the high-energy (multi-Regge) limit s ≫ ð−ˆtÞ ∼ q2T ∼ Q2 which is important for Balitsky-Fadin-Kuraev-Lipatov (BFKL) [18,19,20] resummation of ln s=ð−ˆtÞ-enhanced effects. This approximation allows us to derive the factorization formula for Drell-Yan cross section, which is equivalent to the perturbative Collins-Soper-Sterman (CSS) formalism [21] for jqTj ≪ Q and accuracy of which at jqTj ∼ Q is expecpteffidffiffi to increapseffiffiffipowerlike with decreasing values of jqTj= S and Q= S.
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