Implementation of Novel NLO Matching Schemes for p p > Z Z

Sammanfattning

The task of matching fixed-order event generation with the parton shower is physically non-trivial and closely related to an efficiency bottleneck of event generators. In this thesis, we examine and implement two novel matching schemes in KrkNLO and MAcNLOPS for the LHC process p p > Z Z. As both schemes generate positive-definite event samples, they can be interesting alternatives to MC@NLO. The implementation of KrkNLO will be modified compared to original formulation, allowing MSbar PDFs to be used. Whereas for MAcNLOPS, this will be its first implementation. Both implementations rely on MadGraph5_aMC@NLO (MG5_aMC) and PYTHIA8 for hard event generation and parton shower respectively, using also elements of MG5_aMC for the matching procedure. The results are obtained for various distributions sensitive to matching schemes or valuable for practical purposes. In both cases, the results agree well with MC@NLO up to the higher order effects. For KrkNLO, it was additionally observed to be insensitive to factorisation scheme choice.