Off-shell initial state effects, gauge invariance and angular distributions in the Drell-Yan process

TL;DR

This paper investigates the effects of off-shell initial state partons on Drell-Yan lepton pair production, emphasizing gauge invariance, comparing different approaches, and validating results against experimental data with predictions for future colliders.

Contribution

It introduces a gauge-invariant parton Reggeization approach for off-shell initial states in Drell-Yan processes and compares it with other prescriptions, highlighting differences in structure functions.

Findings

Good agreement with E-288 experimental data for $q_T$-spectra.

Significant differences found between prescriptions for gauge invariance.

Predictions provided for Drell-Yan structure functions at NICA collider.

Abstract

We discuss production of Drell-Yan lepton pairs at hadron colliders in the framework of the parton Reggeization approach, which includes off-shell initial state effects in a gauge-invariant way. Other possible prescriptions to restore gauge-invariance of hard-scattering coefficient with off-shell initial-state partons are also investigated and significant differences for the resulting structure functions are found, especially for the $F_{UU}^{(\cos2\phi)}$. We compare our numerical results for $q_T$-spectra of the lepton pair with experimental data, obtained by E-288 collaboration ($\sqrt{S}=19.4$ and 23.8 GeV) and find a good agreement. Also we perform predictions for the Drell-Yan structure functions at NICA $pp$-collider ($\sqrt{S}=24$ GeV).