Off-shell particle listed in lhe file

Dear Matthew,

I'm not sure I understand your question and what you mean by 'real' and 'virtual' Z-bosons. If the Z is written in the event-file it doesn't mean that that Z-boson is a real Z. Similarly in for the 'virtual' Z boson.

For bwcutoff=15 I can easily have two lepton pairs with invariant masses around 60GeV, compatible with a 125GeV mass Higgs boson, which means that the code writes two intermediate Z-bosons in the event file.

Best regards,
Rikkert

Thanks Rikkert Frederix, that solved my question.

Dear Rikkert,

Thank you for your answer.

First, sorry for the confusion with the "real" and "virtual" particles. That was meaningless.

From what I understand, Two things - (1) MZ +- bwcutoff*WZ = 91 +- 37 GeV approximately, and (2) 60 GeV is within this range - mean that two Z bosons of masses 60 GeV can be listed as on shell.

If this is not a correct interpretation of your answer, please tell me where I am mistaken.

If it is, I still have a difficulty with the listing/omission of the Z bosons in the list.
Here is one event that troubles me:
1. The combined mass of the four leptons add up to 125 GeV, which is consistent with the mass of Higgs.
2. Both Z's are listed, which may happen as long as both masses are within 91 +- 37 GeV range.
3*. One Z has around 90 GeV, while the other has around 15 GeV of invariant mass. Surely, the 15 GeV mass lies outisde the range? Why is it listed?

Thank you for your time,

Matthew

Hi Matthew,

That's indeed a bit surprising. Can you attach here the exact proc_card, param_card and run_card that you used? I'll try to reproduce your results.

Best,
Rikkert

Dear Rikkert,

Here is the DropBox link to proc_card.dat, run_card.dat, and unweighted_events.lhe that I obtained from generating the events (I couldn't figure out a way to attach files here). I hope it works.

https://www.dropbox.com/sh/dx0hgotiupytr8g/AABIVabCzZSPnfZpFrw_ow-ea?dl=0

I don't recall making changes to these cards: they should be the same as the default values.
The exact syntax used to generate the events is the one I posted in the first question.

Thank you,

Matthew

Dear Rikkert,

It worked! All of the on-shell Z masses (that I looked at so far) lie within the range.

Also, here is what I did alternatively:
I thought the cause of the problem might be the syntax (h > z z > mu+ mu- mu+ mu-), so I tried to avoid it.
0. myamp.f was not changed.
1. generate p p > t t~ h, (t > b w+, w+ > mu+ vm), (t~ > b~ w-, w- > mu- vm~), (h > z mu+ mu-, z > mu+ mu-).
(This would include only the subprocesses in which at least one of the Z's are on-shell)
2. add process p p > t t~ h, (t > b w+, w+ > mu+ vm), (t~ > b~ w-, w- > mu- vm~), (h > mu+ mu- mu+ mu-).
(This would add the feynman diagrams in which both Z's are off-shell)
3. output, launch, etc.
For this method as well, all of the of the on-shell Z masses lie within the range.
I will have to check if this is gauge/Lorentz invariant.

But anyhow, thank you so much for your help! This would have been impossible on my own.

Best,

Matthew

Thanks Rikkert Frederix, that solved my question.