Hi all,
I am a bit stuck with the pstartfactor calculation. Well, it is
not the actually calculation but the reweighting of the data sample. I
will outline in this mail the problem and we can discuss it in todays
meeting.
The p*factor is calculated from generic BB sample. This sample is used for
the Vcb AND Vub components which avoids to fix (or know) the ratio between
the two samples. The P*factor is then quite simple:
e^u_t e^u_l N^u_l BF(B->clv)
--------------- = ------- * ------------
e^sl_t e^sl_l N^sl_l BF(B->ulv)
The sample has the same luminosity and cross section for B->clv and
B->ulv. So, that's easy.
Now the difficult part. For the Vub component, we like to apply the usual
reweighting, that means rescaling the resonant decays and reweighting the
non-resonant part. Rescaling the resonant decays is straight forward as
the BF in generic and signal MC are the same. The other part is the tricky
part.
First, the generic non-resonant part is already reweighted. Here I can
take the weights from the MC production and reweight the distribution to
an unweighted one. Then I can apply the standard weights used also for the
MC signal sample.
Second, how do I fix the total b->ulv BF or how do I get the total b->ulv
BF? Maybe the later approach is easier. I can sum the new BF for the
resonant decays. This gives me the exclusive BF. How to I get the
inclusive BF? Are the weights normalised in such a way that the inclusive
BF will remain invariant?
Any comments on this?
Cheers,
Wolfgang
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Wolfgang Menges
Queen Mary, University of London SLAC, MS 35
Mile End Road 2575 Sand Hill Road
London, E1 4NS, UK Menlo Park, CA 94025, USA
++44 20 7882 3753 ++1 650 926 8503
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