[Rivet] how to use W/ZFinders for WZ analysis

[Roman Lysak]

   Dear Rivet authors,

I'm trying to run Rivet analysis which selects one W and one Z boson 
which both decay to electrons or muons (see the attachment).
In the analysis, I try to use W(Z)Finder projection.

There is one problem when having events where both W and Z decay to 
leptons of the same flavor (e.g. three electrons in final state): W and 
ZFinder can use the same leptons to find W/Z boson.
Therefore, we apply the condition on W/Z leptons that they are not the 
same (see lines 95-102). However, this is not ideal thing to do, since 
there could be some events we are loosing with such condition (other 
leptons could form W bosons too).

I tried to use VetoedFinalState::addVetoOnThisFinalState() (see lines 
40-50) in order to restrict the particles WFinder can use (ZFinder uses 
all of the particles).
However, this seem to have no effect and I still get the same numbers 
(cross-section) as before when I did not apply this veto.
Actually, the cross-sections are quite different depending whether we 
use (or not)  our condition on leptons from W/Z not being the same 
(about 50% difference).

Could you suggest what would be the best procedure to use to solve this?

Thanks a lot,
   Roman Lysak

P.S. I'm using Rivet 1.7.0, but as far as I understand there is the same 
functionality for W/ZFinder in Rivet 1.8.0 just with a little bit 
different syntax.

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