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Vub measurement using recoil of fully reconstructed Bs

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Subject:
From:
Kerstin Tackmann <[log in to unmask]>
Date:
24 Nov 2003 10:51:06 +0100 (MET)Mon, 24 Nov 2003 10:51:06 +0100 (MET)
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Hi,

we have used our reduced ntuples for Vub signal for VubFit (and your files
for the generic MC and data). We see some differences in the fit results.
Please find logfiles for the fit using your reduced signal MC ntuples
here :

http://www.slac.stanford.edu/~kerstin/vubfit/s00_result_nocat.dat

and for the fit using our reduced ntuples for Vub signal here:

http://www.slac.stanford.edu/~kerstin/vubfit/all_result_nocat.dat

for the comparison. The plots using your reduced ntuples for the Vub
signal:

http://www.slac.stanford.edu/~kerstin/vubfit/s00_mxresult.eps

and the plots using our reduced ntuples for Vub signal:

http://www.slac.stanford.edu/~kerstin/vubfit/all_mxresult.eps

Should we worry because of the small differences?


We also compared the files (again the Vub signal MC) in a few variables
and here are the results (all the three years together):

NONRES
******
                              your files                  our files
# Breco candidates:            202442                       202496
# Breco cand. with mes>5.27     24365                        24358
# events with pcms>1.            6157                         6097
# events with |Gvxbtyp|==7     194735                       194784
# events with |Gvxbtyp|!=7       7707                         7712

MIX
***
                              your files                  our files
# Breco candidates:            297479                       296048
# Breco cand. with mes>5.27     36076                        35757
# events with pcms>1.            8976                         8839
# events with |Gvxbtyp|==7     182942                       182986
# events with |Gvxbtyp|!=7     114537                       113062
# events with kplus>0.         190560                       190629

The two most important things might be:
1. We are seeing some more Breco candidates, but noticeably less leptons.
What could be the reason for this?
2. There are differences in Gvxbtyp, which, to my understanding, only
depends on truth information of the events. How can these differ between
your and our files?


Ric mentioned earlier that small differences can be due to minor changes
in the (Breco) code. But we think Alessio said that the instructions page
for IslBrecoilUser has the tags that you actually used when producing your
ntuples. We used the tags given there as well. If we used the same tags,
how can we get differences in the ntuples?

One more question about the Gvxbtyp variable as it is filled in
mcTruth.icc:
If two semileptonic B decays are present in one event Gvxbtyp is set to
the value that corresponds to one of these decays while the information
about the other one is lost for this variable (e.g. in your nonres file,
there are events for which this variable is not 7 or -7 although each of
the events contains one b B -> X_u l nu decay). Why are you doing it this
way?

Thanks,
Kerstin




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