Difference: TheorySystematics (13 vs. 14)

Revision 142019-01-18 - ReinhardSchwienhorst

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META TOPICPARENT name="LHCTopWGInternal"

Theory systematics

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Signal (ttbar and single top) TH systematics

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Note that this page is outdated as of January 2019. Information on currently used TH systematics can be found in the ATLAS and CMS papers.
 
  • Generator modeling: comparison of central predictions from generators. Other sources not ending in one of the following categories and specific to a certain analysis may end up here (example: DR vs DS scheme for ttbar subtraction in Wt). General guidelines suggest to use for the ttbar signal at least one multileg generator and at least one NLO generator, and for single top at least two different models (one of which NLO). Differences coming from the use of different (tuned) PS models can also end up in this category whenever it is clear this is not already covered by the explicit systematic error on the description of radiation (and hadronisation).
    • to be discussed: do we want to leave this error optional, only for when the difference between the two predictions goes outside the band from the error on radiation (and hadronisation)?
    • some authors advice, for observables at NLO precision, to also quote the uncertainty from interfacing the prediction to two different parton showers. While this is a conservative approach, it is under discussion how to quantify the amount of double counting of the uncertainty coming from hadronization effects.
 
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