Hi Concezio,
On Tue, 23 May 2006, Concezio Bozzi wrote:
> Hi Wolfgang,
>
> technically speaking, I think that the pstarsample dataset, already
> implemented in VVF by Roberto, does what you need. That dataset contains
> vcb and vub events from the same ntuples (generic MC), and the vub
> events are reweighted as usual, except the magic k factors which are
> used to normalize generic MC and signal MC to the same luminosity. So if
> you compute the pstarfactor from the pstarsample you should be done.
Well, yes, I am looking at Roberto's code, but there was at least one bug,
and then the problem of non-resonant reweigting. It is the generic sample,
and this is already weighted at production time. If you just reweight it
again, that is clearly wrong.
I thought the magic k factor is only needed to normalise the resonant
signal MC sample to the non-resonant signal MC sample.
Cheers,
Wolfgang
> The trick with the total charmless BF is the following. When you apply
> the reweighting to the non-resonant MC you also inflate at the same time
> the non-resonant BF in MC, which is a factor ~2 lower than what we see
> in data. Indeed, different weight files were produced in the past which
> correspond to different values for the total b->ulnu BF, as measured
> e.g. in the mX, or the q2-El, or the endpoint analyses. For this reason,
> after reweighting non-resonant events and rescaled resonant BFs, the
> BF(B->ulnu) which you need in order to obtain the pstarfactor is the one
> corresponding to the weight files you are using. Last time we used a set
> of weights corresponding to BF(B->ulnu)=0.00224, the PRL mX result.
>
> A small complication arises when doing the unfolding. In this case the
> formula for the pstarfactor should have the PBF(B->ulnu), due to the
> kinematic cuts. In other words, you should multiply BF(B->ulnu) by the
> DFN acceptance. You get the latter from getEffFromDFN in VirUtil in the
> 1D case, or from getEffFromDFN2D in the 2D case.
>
> Talk to you later, Concezio.
>
>
> Wolfgang Menges wrote:
>
> >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
> >
> >-----------------------------------------------------------------------------
> >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
> > [log in to unmask]
> >-----------------------------------------------------------------------------
> >
> >
>
>
-----------------------------------------------------------------------------
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
[log in to unmask]
-----------------------------------------------------------------------------
