sherpa is hosted by Hepforge, IPPP Durham
close Warning: Can't synchronize with repository "(default)" (/hepforge/svn/sherpa does not appear to be a Subversion repository.). Look in the Trac log for more information.

Changes between Initial Version and Version 3 of Ticket #69


Ignore:
Timestamp:
Apr 29, 2010, 1:36:46 PM (14 years ago)
Author:
Frank Siegert
Comment:

This is fixed on Sherpa SVN but will need to be thoroughly tested before it can be released.

Legend:

Unmodified
Added
Removed
Modified

  • Ticket #69

    • Property Version changed from trunk to 1.2.1
    • Property Summary changed from Inclusive "P b bbar" cross section to Cross sections for processes with mixed orderEW/orderQCD diagrams

  • Ticket #69 – Description

    initial v3  
    1 Sherpa's cross section for `pp -> P b bar` around the Z->b bbar peak doesn't reproduce the one in Madgraph if the following cuts are applied:
     1When generating processes without fixing the Order_EW or Order_QCD of the diagrams, Sherpa will wrongly enhance the interference between diagrams of different Order_EW/Order_QCD. This is not a problem in any of our default setups, because there we restrict the Order_EW, but if one includes all (e.g. because of cuts which enhance the EW contributions such that they are needed), one will run into this bug.
     2
     3Example: Sherpa's cross section for `pp -> P b bar` around the Z->b bbar peak doesn't reproduce the one in Madgraph if the following cuts are applied:
    24 * pT(photon) > 200 GeV
    35 * pT(b) > 50 GeV
    … …  
    1315If I select the resonant diagrams only, i.e. `pp -> P Z[b bbar]` then Sherpa (0.005917 pb) and Madgraph (0.005869 pb) agree well.
    1416
    15 I attach four setups:
    16  * Madgraph inclusive (inc_proc_card.dat + run_card.dat)
    17  * Madgraph resonant (cut_proc_card.dat + run_card.dat)
    18  * Sherpa inclusive (Run.inc.dat)
    19  * Sherpa resonant (Run.cut.dat)
    20 
    21 I have checked that the generated diagrams are the same. If I haven't overlooked something the above mentioned cuts should be implemented in both setups (and since the resonant XS is consistent, this seems to work).