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Vub measurement using recoil of fully reconstructed Bs

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Subject:
From:
Antonio Petrella <[log in to unmask]>
Date:
05 Jul 2006 17:16:56 +0200Wed, 05 Jul 2006 17:16:56 +0200
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Hi all,

today I've run again two fit tests, one with the ratio signal/peaking 
bkg fixed (only on data, this time) and one without fixing the ratio.

Results can be found here:

http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fixed/ 
http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_SUN/

General comments:

-comparing the right lower plot (which contains the sum of Bch and B0 
for data)

http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fixed/test_fixeddatachop_all-1.eps
http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_SUN/test_SUNdatachop_all-1.eps

we see that the effect of fixing the ratio is to increase the 
distribution in the low mx region ( 1.55 < mx < 2.1) and to decrease in 
the high mx region (mx > 2.8 ).

So we looked with more attention to fits performed bin by bin to compute 
the correction factor and...:

- the fit in the high mx region for MC depleted has peaking background 
consistent with 0
http://www.slac.stanford.edu/~petrella/tmp/AWG38/depleted/MCsameEND/MCfit_1D_3.103.40.eps 

http://www.slac.stanford.edu/~petrella/tmp/AWG38/depleted/MCsameEND/MCfit_1D_3.403.70.eps

moreover in the Enriched MC the signal and the peaking components are 
swapped for 3.1 < mx < 3.4!
 
http://www.slac.stanford.edu/~petrella/tmp/AWG38/enriched/MC/MC_enrich_1D_3.103.40.eps


- in the low mx region the increase in the mx distribution is due to the 
behaviour of the double ratio (sig/peak)_DATA/(sig/peak)_MC, where the 
numerator and denominator go in the opposite direction i.e.: for MC the 
ratio is small while for data is high, so the net effect of the double 
ratio is to give a high correction.

But fits on MC present clearly some problems: look at

http://www.slac.stanford.edu/~petrella/tmp/AWG38/depleted/MCsameEND/MCfit_1D_1.551.90.eps
http://www.slac.stanford.edu/~petrella/tmp/AWG38/depleted/MCsameEND/MCfit_1D_1.902.20.eps

So I don't think we can trust 100% the numbers used to compute the 
correction so far.

Antonio



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