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Hi Kerstin, I am not sure I understand your point... the charged/neutral B correction is applied on B+ montecarlo and takes care of the fact that the semi-exclusive reconstruction works differently in data and MC. For instance we don't simulate all the decay modes we reconstruct in data, so we need to rescale the MC charged/neutral B ratios to what we see in data. Since we are correcting for Breco effects, we compute the correction factors at the level of the semileptonic events selection and carry them over the entire analysis afterwards. The mixing correction is applied on neutral B mesons only, and separately on data, signal MC and background MC. It is independent on data/MC yields for charged and neutral Bs. Ciao, Concezio. PS: tomorrow Italy celebrates the end of WWII, so I guess we won't show up for the meeting... Kerstin Tackmann wrote: >Hi, > >sorry, I realized that the email below misex up same and opposite sign >events. We use the ratio between charged events and opposite sign neutral >events, of course. Sorry about that. > >But apart from that, why was it done the way it was? I'd just like >to understand and see if we should be doing the same... Daniele? Concezio? > >Thanks, >Kerstin > > >On Tue, 18 Apr 2006, Kerstin Tackmann wrote: > > > >>Hi all, >> >>I have a question concerning the correction we apply to reweight the MC >>to have the same ratio of charged to neutral B as data. >> >>More precisely, we apply this correction to all types of MC (signal, >>b->clnu, other) and we really only use the same sign events for the >>neutral B decays. >> >>Here is what I wonder about: When we do the mixing correction (see BAD >>540 section 5.2.1), we assume that among the neutral B, all the leptons >>we call signal leptons arise from direct (B->Xclnu) and from cascade >>decays, mixed and unmixed in both cases. In signal MC, we will not have >>any cascade leptons from D decays, so the ratio between same sign and >>opposite sign events will be different in signal MC and in b->clnu MC >>and in data. >>This means that also the ratio between charged B and same sign neutral B >>events will be different in data (which, with the few cuts applied here, >>will be mostly b->clnu and hence has cascade leptons from D) and signal >>MC. Yet we reweight the signal MC to have the same ratio. >>So it seems we take the cascade leptons into account for the mixing >>correction, but not for the correction between charged and (same sign) >>neutral B decays. Was there an explicit decision to do it this way? >>If so, why? Does whoever implemented it this way remember the reasoning >>behind this? >> >>I stumbled over this when I went through the VVF code to see how this >>correction should be applied to the spectral unfolding specific >>data sets. However, this seems relevant for the BRBR extraction as well. >> >>Thanks, >>Kerstin >> >> >> >>