What is Double Parton Scattering?

TL;DR

This paper investigates double parton scattering processes, addressing the mathematical singularities involved, and provides a framework for their factorization, evolution, and experimental interpretation in high-energy physics.

Contribution

It introduces a method to handle delta(z_ot=0) singularities in double parton scattering calculations using factorization and operator renormalization, and computes the evolution of double PDFs.

Findings

Handling of singularities via factorization and renormalization

Calculation of double PDF evolution including mixing with single PDFs

Discussion on experimental probes of parton correlations

Abstract

Processes such as double Drell-Yan and same-sign WW production have contributions from double parton scattering, which are not well-defined because of a delta(z_\perp=0) singularity that is generated by QCD evolution. We study the single and double parton contributions to these processes, and show how to handle the singularity using factorization and operator renormalization. We compute the QCD evolution of double parton distribution functions (PDFs) due to mixing with single PDFs. The modified evolution of dPDFs at z_\perp=0, including generalized dPDFs for the non-forward case, is given in the appendix. We include a brief discussion of the experimental interpretation of dPDFs and how they can probe flavor, spin and color correlations of partons in hadrons.