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Hi all, I think there is another issue to be addressed. Up to now, we have been worrying about fixing the signal/peaking background components in our mES fits, to deal with instabilities in bin of kinematic variables with low statistics. We implemented constraints on the signal/peaking background components for mES distributions as a function of the bins of the kinematical (mx, p+, q2) variables, but only for DATA. However, our final mx, p+, mx/q2 fits need also distributions for Vcb+other MC and Vub(IN+OUT) signal MC. These MC components have been and are currently being determined by performing mES fits as usual, e.g. by leaving the signal, peaking and combinatorial backgrounds floating and without any constraint applied. There are plenty of mES fits on MC with low statistics. Recall also that every single bin in the kinematic variable under study results from an appropriate sum of mES fits performed separately on charged B, neutral B opposite flavor and same flavor to correct for BBbar mixing. If you look e.g. at Antonio's latest VVF fits in http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fixed/ you see that mES fits on data http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fixed/test_fixedmES_data3.eps (charged B) http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fixed/test_fixedmES_data4.eps (neutral B opposite flavor) http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fixed/test_fixedmES_data5.eps (neutral B same flavor) have the peaking/signal fixed (only signal S, combinatorial background B and argus shape ar are floating in the fits), whereas the peaking background component P is also floating in the MC mES fits: Vcb+other http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fixed/test_fixedmES_vcboth3.eps http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fixed/test_fixedmES_vcboth4.eps http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fixed/test_fixedmES_vcboth5.eps VubIN http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fixed/test_fixedmES_vubin3.eps http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fixed/test_fixedmES_vubin4.eps http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fixed/test_fixedmES_vubin5.eps VubOUT http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fixed/test_fixedmES_vubout3.eps http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fixed/test_fixedmES_vubout4.eps http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fixed/test_fixedmES_vubout5.eps The bottom line is: we need to constraint somehow the signal/peaking background components in the mES fits also for these MC samples. The question is: how? One possible solution is to use the full (charged + neutral B) MC sample which has been used to correct for the data, but Antonio showed in his previous posting that the fits are not stable for high mx values (signal and peaking background are swapped), and are not good for intermediate mx values. Grouping several high mx bins seems not to give more stable results. Another possibility (which can also be applied when constraining S/P = signal/peaking on data) is to determine separately S and P, by e.g. counting or fitting for S in events with truebrecomode==recobrecomode, and fitting ony P and the combinatorial background in events with truebrecomode!=recobrecomode. This latter solution should give more robust estimates. In any case, any S/P constraint would be determined on the entire (charged+neutral B) sample, and it should be dependent perhaps only on the kinematical variables. Any comments? Ciao, Concezio. Antonio Petrella wrote: > Hi, > > we also computed a correction factor for the signal/peaking bkg using > the entire mx distribution, not a bin by bin. > > In this case the fit looks better, with respect to the bin by bin one: > > http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fix129/test_fix129fitresults.eps > > http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fixed/test_fixedfitresults.eps > > > cheers, > Antonio