Hi Kerstin,

there is something I do not fully understand.
For set 2 the errors on the moments for mxhad
are smaller than those for set 1.

Heiko

On Sat, 15 Jan 2005, Kerstin Tackmann wrote:

>
> Hi,
>
> this will be a little lengthy, but it I guess it is interesting for the
> decision about the kinematic fitter (for both the (mX) BRBR and the
> mX unfolding).
>
> I ran the VirVubFitter jobs on generic MC using the same genMC files for
> the generic MC and as data (as we said on Friday). This uses the ichep
> ntuples. You can find the VirVubFitter output in the following directory
> at SLAC: ~kerstin/scra.
> Taking the numbers from the results.dat for the fitted numbers of events
> in the first bin (0..1.55GeV) I find
> S/N(mxhadfit) = 1.04
> S/N(mxhad)    = 0.98
> so the difference is a lot smaller than what Roberto saw on data if I
> remember correctly. Maybe someone could check my numbers to make
> sure I did not mess it up?
>
>
> Also I computed the moments for the unfolded spectra. Please find the
> tables in here:
> http://www.slac.stanford.edu:~/public_html/vubfit/moments_data.pdf
> The systematics evaluated are the same we had on Friday:
> statistical (on spectrum and detector matrix), multiplicity category
> reweighting, B->Xclnu BFs, exclusive D BFs, mb and a from Belle, B->Xulnu
> BFs (as done for ichep).
>
> The first four pages have tables for the uncorrected and the bias
> corrected moments as obtained on data for mxhad and mxhadfit. Comparing
> the uncertainties it looks like we see quite larger uncertainties on some
> of the moments using mxhad. This is coming mostly from the systematics
> (see the tables where the uncertainties are split up). I tried to figure
> out where this comes from. First having a little closer look at the error
> bars on the left plot on page 4 of VR011105.pdf from last Friday you can
> see that we have larger error bars for mxhad than for mhadfit, so this is
> consistent.
> The corresponding covariance matrices for the theo and the B->Xulnu
> branching fraction uncertainties on the MEASURED spectrum show somewhat
> larger uncertainties using mxhad than unsing mxhadfit. The difference is
> larger when comparing the covariance matrices on the UNFOLDED spectra and
> results in the larger uncertainties on the moments, which you see in the
> tables. This cannot be due to "bad toys", since the evaluation of these
> two uncertainties does not use toys.
> We also see enlarged uncertainties on some moments from the B->Xclnu and D
> branching fraction uncertainties when using mxhad. This does not seem to
> be due to "bad toys" either. I used 1/4 of the respective covariance
> matrices for tests and so not see a change in the relative size (bad toys
> would become less likely when using smaller covariance matrices).
>
> My current guess is that the worse resolution in mxhad is the reason for
> the enlarged uncertainties, but I am not sure how to make a meaningful
> test for this.
> What I tried is to just use the detector response matrix using mxhadfit
> when evaluating the B->Xclnu and D BF uncertainty for the mxhad spectrum
> and I see that the effect gets smaller. So this backs the guess at least.
>
> The following pages show the moments of the unfolded spectra using generic
> MC, first for the Set 1 and the Set2 for which we showed the plots on
> Friday and then for the case where we do not split up the MC sample but
> rather use the full sample for both genMC and as data. Please have a look
> and check if you think they are close enough for mxhadfit and mxhad.
> There does not seem to be enlarged uncertainties for mxhad with respect to
> mxhadfit, but these uncertainties are primarily statistical (and we do not
> see a big enlargement for the statistical uncertainties on the moments for
> the data either, compared to what we see for the systematics).
>
> I compared the theo and B->Xulnu BF systematic uncertainties on BRBR for
> mxhad and mxhadfit, but there I do not see a large difference:
>
> for mxhadfit: +8.2% -7.5% (theo) +- 6.5% (B->Xulnu)
> for mxhad   : +8.6% -7.5% (theo) +- 6.6% (B->Xulnu)
>
> I assume someone has something set up to do the same for the B->Xclnu and
> D BFs since it was done for the summer results. I copied my results.dat
> files for this to ~kerstin/ebr/. There is also the file giving the
> corresponding mean value (mxhadcleo).
>
> With the Run1+2 statistics those systematics we evaluated for mxhad seem
> to be larger than the same ones for mxhadfit when looking at the moments
> (I also see this in the covariance matrices).
>
> At least for the theo and B->Xulnu BF systematics I do not see such a
> large difference for BRBR between mxhad and mxhadfit. Maybe someone should
> check the B->Xclnu and D BFs?
>
> Cheers,
> Kerstin
>
>