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Hi, I agree we cannot correct SP5 to look like SP6. However, by determining separate correction factors we definitely get a better data-MC agreement and get confidence that the fit is working OK. Here are the errors on the correction factors: Entire sample (Run1-4, SP5+6): Chi Square of the Fit = 4.48376 NDOF = 7 ratio other/vcb = 0.60 +- 0.07 Vcb comp = 0.188267 +- 0.00631457 Oth comp = 0.113042 +- 0.0125698 This is what Kerstin got on separate samples: > > > **Fit on Run 1+2, SP5: > > > chi2/ndof = 1.64116 (for 7 dof) > > > ratio other/vcb = 0.296045 / 0.287339 = 1.03 +- 0.17 > > > (with errors: > > > Vcb comp = 0.287339 +- 0.0183957 > > > Oth comp = 0.296045 +- 0.0442523) > > > > > > **Fit on Run 4, SP6: > > > chi2/ndof = 1.90748 (for 7 dof) > > > ratio other/vcb = 0.117799 / 0.141224 = 0.83 +- 0.13 > > > (with errors: > > > Vcb comp = 0.141224 +- 0.00785652 > > > Oth comp = 0.117799 +- 0.0174853) A couple of warnings 1) I previously run the fits WITHOUT the B&D reweighting (-b -d flags), so I run them again and the ratio on the entire sample went from 0.55 to 0.60. I hope Kerstin was more clever than me and run with -b and -d ;-) 2) Wolfgang mentions that the signal has been reweigthed to match the Run1+2/Run3+4 luminosity ratios ub data. A point related to this is: what happens if you run on Run1+2 or Run4 only? In this case you should not apply any reweighting at all and you should also use different magic factors. Did anybody check this? A similar reweighting should be done for vcb+other background, I guess. Ciao, Concezio. Il giorno gio, 20-07-2006 alle 07:40 +0000, Wolfgang Menges ha scritto: > Hi Kerstin, > > Kerstin Tackmann wrote: > > Hi Concezio, > > > >> if we stay with SP5/6 I think that reweighting the D** wrt D+D* > >> separately for SP5 and SP6 would be the best we can do. But this means > >> that we need to know whether we are analysing SP5 or SP6 events when we > >> build the datasets in VVF, which I am not sure how to do. > >> Using SP8 means a lot of extra work/checks/tunings. > >> However it is not clear to me why when we compute the D** reweighting we > >> get 1 for SP5 and 0.83 for SP6, whereas we get 0.55 for (sp5+sp6). Well, > >> the fit might be just readjusting itself... > > Would we actually want to trust it if it is readjusting by so much? > > > Well, checking with data would be better but we have to rely on MC here. > One thing nobody meantioned is the error on this ratios or the ratio > of the D** components to the total background. > > And you can see clearly from the numbers that something else is going > on. Otherwise you will not end up with (1+0.83)/0.55. Or is this to naive? > > Cheers, > > Wolfgang >