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Hi, I guess you are right my next suggestion is to cut on purity from the start, i.e. consider only events with a higher purity of the indivual modes. http://www.slac.stanford.edu/~rfaccini/lost+found/purcut.eps shows the distribution of the purity for generic MC events and the cuts that we apply at analysis level (we require the events to have a purity higher than a given one). It looks like we can save quite some time and space if we request for istance that all events have at least one candidate with a 8% purity. opinions? ciao ric On Fri, 16 Apr 2004, Oliver Buchmueller wrote: > > > > It is certainly worth to test whether or not the normalization to > semileptonic events will work and perhaps even improve the > extraction of the BR(bsg). However, given the fact that there > is at least one thesis a stake I would still vote for a production > without cuts - unless someone can proof that an alternative way will work > as well. > > my two cents ... > > Oliver > > > > On Fri, 16 Apr 2004, Riccardo Faccini wrote: > > > hmmm, I see the problem ( ehem and I was among those who thought > > Fabio's thesis...). > > You can normalize to the number of semileptonic events. In this case you > > will be affected by the systematics on the cut on the lepton, but I think > > it will balance the systmatics on the mes fit which will be reduced. > > > > What do people think? > > ciao > > ric > > > > ______________________________________________________ > > Riccardo Faccini > > Universita' "La Sapienza" & I.N.F.N. Roma > > tel +39/06/49914798 Fax.: +39/06/4957697 > > http://www.slac.stanford.edu/~rfaccini > > Univ. La Sapienza. 2,Ple Aldo Moro, I-00185 Roma Dipartimento di Fisica > > > > "I don't understand what you say, but I believe I disagree" > > > > On Fri, 16 Apr 2004, Henning Ulrik Flaecher wrote: > > > > > > > > > > > Hello, > > > > > > I just noticed that the filtering on leptons and photons above a certain > > > energy cut is (most likely) not an option for the bsg analysis as for the > > > branching fraction measurement we need to normalise to an unbiased B > > > sample and so the full Breco sample. > > > This is how it has been done for Fabio's thesis. > > > Requiring a lepton or photon with a certain energy will most likely bias > > > our normalisation sample, e.g. all B->charged hadron decays would be > > > lost, a fraction of the SL decays etc. > > > The reason why the b->ulv analysis can live with this cut is because they > > > measure a double ratio of branching fractions, so they can normalise to a > > > sample with the same cuts applied. > > > At the moment I can't see how we can get around this but appreciate any > > > ideas! > > > > > > Cheers, > > > Henning > > > > > >