Cross sections with cut lines vs. inclusive do not agree

[Frank Siegert]

Bill Murray looks at three runs:

1. "inclusive" process pp -> gamma b bbar
2. "background" process pp -> gamma b bbar (with Z disabled as particle)
3. "signal" process pp -> gamma Z[b bbar].

Looking 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).

[anonymous]

The factor 3 reported above was not found from putting the higgs mass to 400 GeV (although I did try that, I saw H to ZZ to mumubb which confused the issue)

I simply disabled the higgs in the control cards - that gave the

discrepancy. So I think this is a different probblem.

Bill

[Frank Siegert]

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.)