Hello,
 after scratching my head for 1 day I found why the reweighting at
generator level was not doing what I expected it to do (i.e. just reweight
the mX distribution). The problem is that the way Sven implemented it,
first k+ was extracted and then the value of mx is extracted and
reweighted according to the given weights.

This means that if there is a correlation (as there is) between the
distribution of k+ and mX, the final distribution of mx was not just the
reweighted one [ just to see this visually, if mx and k+ where completely
correlated then the weights would have been completely irrelevant because
he would have kept doing an hit&miss on that given value of mx until a
positive answer came out ]

I have now a tested code which applies the weights on the overall
distribution, i.e. the k+ distribution will be distorted. I think this is
what we want, please shout if you disagree.

This said I applied the weights as estimated by Alessio after the Breco
selection in the generator and I made sure the scaling imposed the right
resonant-nonresonant admixture.
The comparison of the integrals is in
http://www.slac.stanford.edu/~rfaccini/phys/vub/theo/integr_gen.eps
The situation is not perfect, but more than acceptable given the different
conditions under which weights were estimated.

At this point I see two possibilities as far as the signal requests are
concerned

a1) redo the weights (changing the code, which means requesting a new
release) at generator level and change the .dec files

a2) covert the hybrid requests into pure resonant requests, since the
weighting needs to be redone anyhow at analysis level for the systematics

As far as the generic is concerned we could

b1) stay as we are, we will anyhow use the other files for the signal

b2) correct the hybrid (needs a collaboration wide poll, but better sooner
than later)

I lean towards the least kaos solution (given also the use we are doing
now of the MC): a2 & b1.

	comments are welcome (I will then extend the poll to ISL)

	ciao
	ric