High width BSM particle not in LHE file
Hi,
So let me start that this is not just a case of this faq: https:/
We are using a model with Vector Like Quarks, and for our example case (VLQ at 1400GeV, kappa=0.4), our decay has a width of around 144GeV. (MG gets this when using auto, also confirmed by our analytical calculations)
In the case where I specify my process by stating the only the final states and restrictions on coupling orders, my VLQ does not appear in the LHE file, regardless of what I set me bwcutoff to be.
I did some tests, with widths of 1, 10, 100 and 130 GeV, the VLQ is written into the LHE file (given a large enough bwcutoff, but as the width is so large, 15 is just fine).
But when testing with 140GeV, the particle is no longer written to the LHE file, it is not necessarily required, but would be useful for some sanity checks we are doing.
To preempt some questions:
-using MG 2.6.2
-We are also considering interference (separately)
Basically the two commands I am trying to compare are:
1) generate p p > j VLQ bb / p t t~ tp tp~ bp bp~ x x~ z h a, (VLQ > WW bb, WW > ferm ferm)
and
2) generate p p > j ferm ferm bb bb / p t t~ tp tp~ bp bp~ x x~ z h a YWB=2
This should give us the same processes, and looking at the feynman diagrams this seems to be the case.
Cross sections are very similar: 0.070pb vs 0.069pb.
When reconstructing the VLQ mass (using the W and b quark) there is a slight difference in the shape of the resonance, but probably not enough to lose any sleep about. See here: https:/
1) is the Full chain and 2) is the fermion final case.
In the case where we specify the full decay chain (command 1) the VLQ does appear in the LHE file.
Our reasoning behind this is as we specify our interference using only the final states and coupling orders we want to be consistent with that, although it seems the difference is small enough that we probably need not worry.
So, is there a reason the particles do not appear in the LHE file, and is the discrepancy in the shape something to worry about?
Cheers,
Ferdi
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