Tuning in the presence of matching
From Wiki Les Houches 09
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* Affect n=1 ME corrections, Pythia, Herwig, Alpgen+Herwig and Sherpa all pretty much agree. For Algen+Pythia there is a significant difference at low pT. Means that PYTHIA tune would be different for usage with & without Alpgen. | * Affect n=1 ME corrections, Pythia, Herwig, Alpgen+Herwig and Sherpa all pretty much agree. For Algen+Pythia there is a significant difference at low pT. Means that PYTHIA tune would be different for usage with & without Alpgen. | ||
- | + | PL slide to be linked here. | |
== Influence of UE on matching and vice versa == | == Influence of UE on matching and vice versa == |
Revision as of 13:25, 13 June 2009
Interested parties: , Piergiulio Lenzi, Vitaliano Ciulli, Peter Skands, Leif Lonnblad, Simon Platzer, Jon Butterworth, Jeppe Anderson, Mario Campanelli, Markus Warsinsky, Matthew Schwartz, Peter Loch, Dieter Zeppenfeld, Giacinto Piacquadio, Paulo Francovilla +...
Chart the problem. Determine some Classic Examples
Effect of ME corrections on low pT end of the Z pT distribution compared for PYTHIA, HERWIG, Sherpa, Alpgen. Some points:
- Affect n=1 ME corrections, Pythia, Herwig, Alpgen+Herwig and Sherpa all pretty much agree. For Algen+Pythia there is a significant difference at low pT. Means that PYTHIA tune would be different for usage with & without Alpgen.
PL slide to be linked here.
Influence of UE on matching and vice versa
How would low x logs affect tunes?
Expect extra events at with high rapidity jets due to:
- large colour singlet contribution. This will have a component with rapidity gaps, and a component where these gaps have been destroyed by UE.
- large colour octet contribution enhanced by low x logs (Jeppes's calculations).
Presumably these effects will distort min bias tunes etc, since this physics is not necessarily in the MC. The first effect actually can be modelled by HERWIG+JIMMY, to some extent at least.
Not: addressed:
- How dependent on matching strategy?
- Are there ways of revamping pre-matched tunes?