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

The European Physical Journal C

B. Cooper¹  J. Katzy²  L. Mijović³  M. L. Mangano⁴  A. Messina⁴  P. Skands⁴ 

[1] Department of Physics & Astronomy, University College London, WC1E 6BT, London, UK;Deutsches Electron Synchroton, 22603, Hamburg, Germany;Deutsches Electron Synchroton, 22603, Hamburg, Germany;CEA-Saclay, IRFU/SPP, bât. 141, 91191, Gif sur Yvette Cedex, France;European Organization for Nuclear Research, CERN, 1211, Geneva 23, Switzerland;

关键词: Large Hadron Collider;    Monte Carlo;    Partonic Shower;    Initial State Radiation;    Monte Carlo Prediction;   

DOI  :  10.1140/epjc/s10052-012-2078-y

来源: Springer

【 摘 要 】

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.

【 授权许可】

CC BY