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Changes between Version 1 and Version 3 of Ticket #18


Ignore:
Timestamp:
Sep 25, 2008, 1:11:15 PM (17 years ago)
Author:
Frank Siegert
Comment:

Thanks for sending me your setup files, I have tried to reformulate the problem description in light of these, hopefully correct this time?

Some remarks:

  • Since your final state is not one to apply CKKW merging on, you should switch it off. To do that, set "SUDAKOV_WEIGHT=0" and "SCALE_SCHEME=G_MEAN_PT2" (or whatever you think appropriate) in the (me) section.
  • In your "no Z" run 2 you are missing lots of diagrams from the "inclusive" run 1, on top of the ones that you are using in the "forced Z" run 3. Some of these are s-channel types, which one can try to include in run 3 (or observe that their cross section is low), but there are also t-channel ones, which might have an impact. That makes it unclear to me whether the sum of 2 and 3 should really coincide with 1.
  • I can't judge which interference effects might appear here between the diagrams in run 1 that you are separating in run 2 and 3?
  • (PS: If you set EVENT_GENERATION_MODE=Weighted you get cross-section normalised histograms automatically.)

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  • Ticket #18 – Description

    v1 v3  
    1 Bill Murray looks at cross sections for a run where he tries to split background process pp -> Z[mumu]bb (with Higgs disabled) from signal process pp -> Z[mumu]H[bb]. Doing both in one run yields a factor 3 different cross section from adding the separately integrated cross sections, even though in this case one would expect the process to factorise fairly well (?).
     1Bill Murray looks at three runs:
     2 1. "inclusive" process pp -> gamma b bbar
     3 1. "background" process pp -> gamma b bbar (with Z disabled as particle)
     4 1. "signal" process pp -> gamma Z[b bbar].
    25
    3 We suspect that it has to do with the Higgs width not being recalculated for the chosen Higgs mass (he was using m_H=400 GeV I think). If this can be confirmed, we would have to calculate the particle width using all vertices found in the model. This is closely related to ongoing work on inclusive hard decays, so FS and FK are going to work on it.
    4 
    5 Next step: Reproduce problem and verify that it has to do with the width.
     6Looking at the b bbar mass around the Z mass he sees a discrepancy between run 1 and the sum of run 2 + run 3 (the former shows a higher peak above the background by about a factor of 2).