[Rivet] Weights in Rivet

[Stefano Frixione]

Hi Andy,
so I gather that the short answer for *existing* Rivet analysis
is "no"?

Concerning:
> It would be great if you could let us know how you would like them to be
> used by default: our plan at the moment is that we write out N copies of
> every histogram as a weight-variation, and build some logic into our
> default plotting tools to turn these groups of variations into displayed
> error bands. This requires that we can clearly identify the groups and
> tell how to combine them... which is specified at the LHE level, but not
> the HepMC one -- right? So the first version might be a bit approximate,
> e.g. always a min-max envelope rather than sometimes a 68% interval,
> sometimes a quadrature sum, etc.
in my opinion, plotting directly the error bands is error prone and
not particularly flexible. It is fine, but one should *also* get
a copy of all desired histograms for each of the scale and PDF
choices, so that a-posteriori manipulations could be done by the user.
For example, you may want a scale error band that corresponds to
all N*N choices, another one thar results only from setting muF=muR,
and so forth. Likewise, one may want to experiment with PDF
combinations. Needless to say, I'm open to suggestions.

Best wishes, Stefano.