Drell-Yan lepton pair production at high energies in the Parton Reggeization Approach

TL;DR

This paper extends the Parton Reggeization Approach (PRA) to Drell-Yan production by employing Reggeized quarks in the initial state and a gauge-invariant Reggeon-Reggeon-photon vertex for q qbar annihilation into a virtual photon. It derives the LO PRA expressions for cross sections and helicity structure functions, using unintegrated PDFs (via the KMR prescription) and a phenomenological K-factor to account for higher-order effects, and analyzes the angular coefficients in the Collins-Soper frame. The authors confront PRA predictions with data across SPS, Tevatron, and LHC energies for invariant-mass, transverse-momentum, and x_F distributions, finding good overall agreement without ad hoc transverse momentum inputs. They also explore the Lam-Tung relation in this high-energy context, providing predictions for LHC kinematics and underscoring PRA as a powerful framework for high-energy QCD processes dominated by Reggeized exchanges.

Abstract

According to extensive theoretical studies of the high energy limit of QCD, inelastic interactions are dominated by the multi-Regge final states. The appropriate gauge-invariant objects, which simultaneously incorporate the transverse momentum degrees of freedom, are Reggeized gluons, quarks and antiquarks. In the present communication we extend parton Reggeization approach to Drell-Yan production of massive lepton pairs. The basic ingredient is a process of Reggeized quark-antiquark annihilation, which is described by the Reggeon-Reggeon-photon effective vertex. We calculate transverse-momentum and invariant-mass distributions of Drell-Yan lepton pairs measured at the CERN SPS, FNAL Tevatron and CERN LHC in the different ranges of energy and rapidity. We focus on angular distributions of Drell-Yan leptons in different kinematical ranges. The obtained results are compared with the existing data and a good agreement is found. The predictions for future experiments for Drell-Yan lepton pair production at the CERN LHC have been made.

Figures (11)

• Figure 1: Differential cross section of Drell-Yan lepton pair production as function of virtual photon mass $Q$. The data are from R209 Collaboration R209. The curve 1 -- $\sqrt{S}=62$ GeV, the curve 2 -- $\sqrt{S}=44$ GeV.
• Figure 2: Doubly differential cross section of Drell-Yan lepton pair production as function of virtual photon mass $Q$. The data are from CDF Collaboration DY_CDF at $\sqrt{S}=1.8$ TeV.
• Figure 3: Differential cross section of Drell-Yan lepton pair production as function of virtual photon mass $Q$. The data are from CMS Collaboration CMSDY at $\sqrt{S}=7$ TeV. Solid line - our prediction normalized to the theoretical value of the cross-cection in the Z-boson region.
• Figure 4: Differential cross section $Q^3 d\sigma/dx_F dQ$ of Drell-Yan lepton pair production as function of $x_F$ integrated over all $q_T$. Curves $1-8$ correspond $Q$ from $4.75$ GeV till $Q=8.25$ GeV with the step equal to $0.5$ GeV. The data are from FNAL fixed target experiment FNALXF at the $\sqrt{S}=38.8$ GeV.
• Figure 5: Differential cross section of Drell-Yan lepton pair production as function of $q_T$. The data are from R209 Collaboration R209 at the $|y|<4$, $5<Q<8$ GeV, $\sqrt{S}=62$ GeV.