 |
 |
On Fri, 9 Dec 2005, Heiko Lacker wrote: > Hi, > > if I'm not mistaken there is a bug (at least in a part) in SP8 > where not all B->D**lnu modes have been simulated. That could > explain the difference you see in the lepton spectra between > data and MC. > > This has been reported at the last Collab meeting. I don't know > where though. I found it: http://www.slac.stanford.edu/BFROOT/www/Organization/CollabMtgs/2005/detSep05/Thur1a/jochen.pdf Here's what it says (look at it yourself for more details): Apparently the branching fractions for the B->Dpi l nu (ie, non-resonant B->Xc l nu) modes were accidentally set to zero in DECAY.DEC. They made a new release with the correct branching fractions, but by then they had already done some simulation production. The result is that for Runs 2 and 3, the total semileptonic branching fraction is 4% too low. This affects semileptonic studies. It looks like Run2 and Run3 will be redone. In the meantime, Jochen proposes (to the simulation people) to: * Provide weighting function to scale up broad D** resonances to get correct semileptonic branching fraction * For the few semileptonic analyses that are sensitive to the shape of the nonresonant contribution, produce a dedicated nonresonant MC sample. But I am not sure if they ever did what he proposed. Happy new year, sheila