Exclusive Monte Carlo modelling of NLO DGLAP evolution

TL;DR

This paper introduces a novel Monte Carlo method for NLO DGLAP evolution that handles exclusive multiparton distributions, improving precision in QCD simulations for collider physics.

Contribution

It develops an exclusive NLO DGLAP evolution scheme using new kernels, enabling more detailed parton shower simulations in Monte Carlo programs.

Findings

The new scheme matches traditional NLO DGLAP at the inclusive level.

High-statistics tests confirm the scheme's practical effectiveness.

The method is suitable for future high-precision QCD Monte Carlo simulations.

Abstract

The next-to-leading order (NLO) evolution of the parton distribution functions (PDFs) in QCD is a common tool in the lepton-hadron and hadron-hadron collider data analysis. The standard NLO DGLAP evolution is formulated for inclusive (integrated) PDFs and done using inclusive NLO kernels. We report here on the ongoing project, called KRKMC, in which NLO DGLAP evolution is performed for the exclusive multiparton (fully unintegrated) distributions (ePDFs) with the help of the exclusive kernels. These kernels are calculated within the two-parton phase space for the non-singlet evolution, using Curci-Furmanski-Petronzio factorization scheme. The multiparton distribution, with multiple use of the exclusive NLO kernels, is implemented in the Monte Carlo program simulating multi-gluon emission from single quark emitter. High statistics tests ($\sim 10^{10}$ events) show that the new scheme works perfectly well in practice and, at the inclusive (integrated) level, is equivalent with the traditional inclusive NLO DGLAP evolution. Once completed, this new technique is aimed as a building block for the new more precise NLO parton shower Monte Carlo, for W/Z production at LHC and for ep scattering, as well as a starting point for other perturbative QCD based Monte Carlo projects.