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Hi, here are some results for the double ratio (signal/peakingBG)_MCenriched ----------------------------- (signal/peakingBG)_MCdepleted as a function of mx. We use this double ratio, multiplied by the ratio (signal/peakingBG) in the depleted data sample, in order to fix the (signal/peakingBG) components in the mES fits on data after all cuts as a function of mx. The various signal (S) and peakingBG (P) components of this double ratio on MC can be computed on either: (1) the entire MC sample, by performing a 3-parameter fit to S, P and combinatorialBG (B) or (2) on separate "signal" (reconstructed Breco mode == true Breco mode) and "background" (reconstructed Breco mode != true Breco mode) samples. In this case, the signal sample is used to determine S, whereas the background sample is used to determine P and B. Method (2) has a number of advantages on method (1): - the uncertainty on S and P is smaller - the bias on S is reduced, since we don't risk to mix up/swap signal and peaking background due to the very similar functional forms of their PDFs. The spreadsheet attached to this message proves the above two statements. The upper part of the spreadsheet contains the results obtained with method (1), the lower part refers to method (2). Look e.g. at the errors on the peaking background numbers on the enriched sample on column E5-E14 for method (1) and E18-E27 for method (2). The same is true on the depleted sample (column Q) and for the signal yields (columns K and W). The bias in method (1) on the number of fitted signal and background events (columns I5-I14, U5-U14 for signal, AH5-AH14, AI5-AI14 for background) is also evident by comparing them to the number of expected events in the datasets (respectively: columns AI18-AI27, AI31-AI40 for signal, AH18-AH27, AH31-AH40 for background). The double ratios which come out are flat as a function of mx and are compatible with 1, see the light blue cells in the spreadsheet, or the attached eps file (The number for the last bin in mx is not meaningful since there are very few events in the mES plot). The bottom line is that the signal/peaking background in the mES fitss can be fixed in our data to the values which we obtain on the depleted sample, times a MC correction which turns to be about 1 within 10% and a ~10% uncertainty, which gets higher at high mx. This is not the end of the story, of course. The study needs to be repeated on the MC samples which we use in VVF (vcb+other, vubIN, voubOUT), since we have to fix the signal/peaking background components in there as well... Stay tuned, Antonio&Concezio.