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Hi all, I repeated the study to evaluate the theoretical uncertainty. First, these are the plots that show the uncertainty due to the Mx cut (the same of the BAD) http://www.slac.stanford.edu/~daniele/vub/sfDependency-0.15-allcuts.eps (second raw is new and rapresent the systematic effect due to the a parameter) http://www.slac.stanford.edu/~daniele/vub/sfError-0.15-allcuts.eps (second raw is new and rapresent the error due to the a parameter) Then, in conclusion, systematics on the eps_mx efficiency is around 15.2%. Unfortunately this is not all we have. In July an additional effect was neglected. Since the efficiency is very dependent on Mx_true (see http://www.slac.stanford.edu/~daniele/vub/mxhadgenvubtheefficiency.eps) a reweighting will affect the overall efficiency (named eps_u) In order to take into account properly both the effects (eps_u and eps_mx) I implemented this reweighting in the fit. The results are mb=4.950 (a=1.290) BRBR -25% mb=4.650 (a=1.290) BRBR +30% a=3.6 (mb=4.800) BRBR +9% a=0.380 (mb=4.800) BRBR -8.5% Then in conclusion the theo. uncertainty should be +31% -26% on the ratio(BR). In July we quoted a factor two less (15%). This difference derives, as mentioned above, from the uncertainty on eps_u that is around +-15% With this uncertainties we are fully dominated by sistematics. A looser cuts on Mx will not help too much since the uncertaity is due to the overall efficiency. Then two questions: - may the multiplicity fit help (in principle it is less affected by efficiency)? I will check this. - may we use a more precise values of mb and a? Daniele