Monte Carlo modelling of NLO DGLAP QCD Evolution in the fully unintegrated form

TL;DR

This paper demonstrates a feasible method to incorporate complete NLO corrections into Parton Shower Monte Carlo simulations for QCD evolution, providing an exclusive, fully unintegrated phase space approach that aligns with standard inclusive results.

Contribution

It introduces a novel Monte Carlo method for NLO DGLAP QCD evolution that is exclusive and fully unintegrated, advancing beyond existing LO-based shower models.

Findings

Feasibility of NLO corrections in Monte Carlo QCD evolution demonstrated.

Exact agreement with standard inclusive NLO DGLAP evolution.

Potential applications in collider physics simulations.

Abstract

Presently available perturbative QCD calculations combining hard process matrix element with the Parton Shower Monte Carlo programs feature hard process matrix element calculated often beyond the leading order (LO), that is including complete next-to-leading-order (NLO), or even next-to-next-to-leading-order (NNLO) corrections, while Parton Shower is only at the leading order (LO). We report here on a work in progress which demonstrate feasibility of constructing Parton Shower Monte Carlo (PSMC) featuring complete NLO corrections to QCD evolution with respect to the logarithm of the factorization scale. This effort presently covers non-singlet subset of Feynman diagrams contributing to the above QCD evolution. It should be stressed that our approach to the NLO QCD evolution is exclusive, that is giving insight into the fully unintegrated phase space. However, at the inclusive level our implementation agrees exactly with the standard inclusive picture of the NLO DGLAP evolution. Our new approach (after including NLO singlet diagrams) provides a complete method of combining the resummed and fixed order perturbative QCD calculations beyond the LO in a form suitable for the MC implementation, an alternative to the existing ones. First practical applications will include Monte Carlo generators for W/Z production processes in hadron-hadron colliders and lepton-hadron colliders.