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Hello Folks, I am trying to implement the new hybrid model in our generator and I am slightly confused. I was trying to check that the generator level distribution of Mx after the generator level reweighting was the same as the reweighted distribution at VubFit level. I was failing and I traced it back to a different nonresonant Vub spectrum. If I compare mxhadgen in /u/ec/ursl/root/anaQA-n00/csx-vubnre.root with the corresponding distribution at generaltor level with no cuts BEFORE ANY REWEIGHTING I get http://www.slac.stanford.edu/~rfaccini/phys/vub/theo/nresnorew.eps (top=generator; bottom = mxhadgen). The mxhadgen distribution is clearly harder, its mean being 200 MeV higher. If I then request the presence of a reconstructed lepton, nle==1, (with pcms>1) I get the agreement in http://www.slac.stanford.edu/~rfaccini/phys/vub/theo/comp_nle.eps which is basically ok. I investigate the possibility of having problems with the brehmsstrahlung, and I found that the generator level reweighting ignores possible bremsstrahlung (i.e. the photon is not assigned to the 'hadronic mass' while it is in our analysis level reweighting. Looking at electrons and muons separately this seems to be a tiny effect, though. I then looked at a possible bias of the b-reconstruction and I actually found a strong dependence of the mean value of mxhadgen with the purity of the mode: http://www.slac.stanford.edu/~rfaccini/phys/vub/theo/mxgenpur.eps (note that at generator level <mxhad>=1.45). This means that the mes sidebands are dominated by high mx states, which makes sense because of combinatorics. In summary: 1) when looking at the generator level mx we need to make sideband subtraction (this might have been obvious to you, but not to me ...) Does anybody have a sideband sub distribution of mxhadgen before any cut so that I can test the generator? 2) are we computing the weights on the sideband subtracted or the raw events? Are we scaling to the #of generic with or without sideband subtraction? I would like to double check the logic of this process because it can be delicate ... 3) I am afraid we have to redo the weights at generator level in order to be sure , also given the brehmstrahlung business ciao ric