[Rivet] CMS RIVET analyses

[Frank Siegert]

Hi Andy, Nhan,

>>> * In the W+jet case, the back-to-back requirement was trying to use two
>>> constituent charged leptons: there should only be one and I'd have
>>> expected the code to segfault when it tried to access the second.
>>
>> This might be my own misunderstanding of the WFinder, but I took the l2 to be the neutrino which I used to define the Phi angle between MET and jet.  It's been a while since I did this so I can't now remember why I came to this conclusion.
>
> Maybe Frank S can confirm, but the neutrino should be in the
> constituentNeutrinos and only one charged lepton in constituentLeptons.
> I checked the WFinder.cc source code and it does look like that's how
> it's being filled.

Confirmed. This was changed back in 1.6.0 where we went from the
ZFinder-like constituentLeptonsFinalState() to separate
constituentLeptons() and constituentNeutrinos(). So maybe the analysis
was validated with an older Rivet version and then simply rewritten
without checking what the new methods do?
I think the current doxygen entries are unambiguously correct there
(size==1), but it would have been clearer to call it e.g.
constituentChargedLepton().

> I'm tempted to rename/alias these functions as constituentLepton,
> constituentNeutrino (singular) for WFinder, to clarify things. Just in

We should decide whether there will ever be a case where multiple
bosons fitting the criteria should be allowed, because then a singular
lepton/neutrino might not be flexible enough. But I can definitely
live with a restriction to only one vector boson (which is what is
currently used in the analyses).

Cheers,
Frank