Importance of a consistent choice of αS in the matching of AlpGen and Pythia

J. Katzy, M. L. Mangano, A. Messina, L. Mijović, P. Skands

Research output: Contribution to journalArticleResearchpeer-review

36 Citations (Scopus)


We consider the impact of varying αs choices (and scales) on each side of the so-called "matching scale" in MLM-matched matrix-element + parton-shower predictions of collider observables. We explain how inconsistent prescriptions can lead to counter-intuitive results and present a few explicit examples, focusing mostly on W/Z+jets processes. We give a specific prescription for how to improve the consistency of the matching and also address how to perform consistent tune variations (e. g., of the renormalization scale) around a central choice. Comparisons to several collider processes are included to illustrate the properties of the resulting improved matching, relying on AlpGen + Pythia 6, with the latter using the so-called Perugia 2011 tunes, developed as part of this effort. Our observations, nevertheless, apply to the large class of tools where matrix-element generators are merged with independent codes for the parton-shower evolution.

Original languageEnglish
Article number2078
Pages (from-to)1-16
Number of pages16
JournalEuropean Physical Journal C
Issue number7
Publication statusPublished - 2012
Externally publishedYes

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