Hi all, most of the causes of the disagreements data-MC and MC-MC are now better understood. I updated the page: http://www.slac.stanford.edu/~daniele/vub/complots/comp.html and I included: * genericMC-cocktailMC comparison in many configurations * data-genericMC with different breco cuts The coclusion are pretty exciting. GENERIC-COCKTAIL comparison: 1) using SP4 cocktail (genericMC is mainly SP4) the comparison improves 2) a cut on the integrated purity (for instance at 60%) improves the comparison both for the shape and for the efficiency. Look for instance at qtot distributions. 3) differences in the qtot are due to small difference in the total number of charged tracks. If we take only Bch the differences are gone. I can say that generic and cocktail ARE THE SAME but - SP3 and SP4 are different - different breco purities imply different efficiency - the fraction of Bch has to be the same DATA-GENERIC comparison: 1) better comparison if we cut on the purity (both integrated and single mode purities) especially for the efficiency as in generic-cocktail comparison 2) break down in B0-Bch helps 3) B0's look perfect!!!! Bch's have good Mxhadfit but very bad mnu**2, Qtot and Mxhadfit!!!!! 4) mnu**2 for Bch and B0 are completely different on MC. On data the distributions seem to be pretty similar. Final conlusions and action items: ---------------------------------- Cocktail-generic comparison problem seems to be gone but we need SIMILAR PURITY and ratio N(Bch)/N(B0) Then, in principle, WE CANNOT USE COCKTAILMC since it does not contain low purity modes (especially bias in the efficiency) B0's are ok on data-genericMC comparison! Strange Bch distributions on the MC. Then: a) we should use generic MC to model the background with a cut on the purity. I propose a cut on the single mode purity (>10%) to remove the superblock 4 present in genric MC. The use of the cocktail imply a correction in order to take care of the low purity modes not present in it. b) we should perform a careful comparison of the Breco modes between data and generic MC and weight properly. The Luigi's work goes in this direction. c) since the statistic of the generic MC is similar to the data one we will introduces a large error due to MC statistics. S/B is 1/2 and then the additional error will be 1.4 times the original one. With a cut Mx<1.5 GeV the ratio S/B goes down ot ~1/1. We should consider this change in the Mx cut. d) we have to understand why some variables for Bch are so different. Actually the kinematic fit seems to correct part of the disagreement. Daniele