Optimizing VBF at NLO

Asked by Richard Ruiz

Hi Folks,

I am aiming to generate a very large and healthy VBF at NLO+PS dataset and wondering if there are any recommendations for optimizing speed and phase space integration.

To be precise, this is not the usual WW or ZZ fusion but W\gamma fusion with an initial-state photon, i.e., q a > q BSM, following the procedure of [1]; See Eq (20).
[1] https://arxiv.org/abs/1602.06957

So while the color structure is marginally simpler than WW/ZZ fusion (my color structure is actually identical to Fig 1c in [1]), I am still dealing with a 2 > 4 system (only one final-state quark). Some optimizations I am considering include
- setting #IRPoleCheckThreshold to -1.0d0 (dangerous, yes, I know)
- activating nevt_job

Are there other (potentially more reasonable) optimizations anyone may recommend, e.g., collier vs ninja, etc?

Many thanks for looking into this!


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marco zaro (marco-zaro) said :

Hello Richard,
for vector boson scattering, a paper has appeared today
There you can find some hints for the generation of this kind of processes, both at fixed order and at (N)LOPS
Note that gamma-quark has never been tried, so problems may arise there. Besides what you mentioned (in particular the pole-check stuff), I think the default sequence of reduction tools (ninja-collier-cuttools in 4prec) is appropriate.

Let us know if you find problems.



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