Hi all,
I think there is another issue to be addressed. Up to now, we have been
worrying about fixing the signal/peaking background components in our
mES fits, to deal with instabilities in bin of kinematic variables with
low statistics. We implemented constraints on the signal/peaking
background components for mES distributions as a function of the bins of
the kinematical (mx, p+, q2) variables, but only for DATA.
However, our final mx, p+, mx/q2 fits need also distributions for
Vcb+other MC and Vub(IN+OUT) signal MC. These MC components have been
and are currently being determined by performing mES fits as usual, e.g.
by leaving the signal, peaking and combinatorial backgrounds floating
and without any constraint applied. There are plenty of mES fits on MC
with low statistics. Recall also that every single bin in the kinematic
variable under study results from an appropriate sum of mES fits
performed separately on charged B, neutral B opposite flavor and same
flavor to correct for BBbar mixing. If you look e.g. at Antonio's
latest VVF fits in
http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fixed/
you see that mES fits on data
http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fixed/test_fixedmES_data3.eps
(charged B)
http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fixed/test_fixedmES_data4.eps
(neutral B opposite flavor)
http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fixed/test_fixedmES_data5.eps
(neutral B same flavor)
have the peaking/signal fixed (only signal S, combinatorial background B
and argus shape ar are floating in the fits), whereas the peaking
background component P is also floating in the MC mES fits:
Vcb+other
http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fixed/test_fixedmES_vcboth3.eps
http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fixed/test_fixedmES_vcboth4.eps
http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fixed/test_fixedmES_vcboth5.eps
VubIN
http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fixed/test_fixedmES_vubin3.eps
http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fixed/test_fixedmES_vubin4.eps
http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fixed/test_fixedmES_vubin5.eps
VubOUT
http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fixed/test_fixedmES_vubout3.eps
http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fixed/test_fixedmES_vubout4.eps
http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fixed/test_fixedmES_vubout5.eps
The bottom line is: we need to constraint somehow the signal/peaking
background components in the mES fits also for these MC samples. The
question is: how?
One possible solution is to use the full (charged + neutral B) MC sample
which has been used to correct for the data, but Antonio showed in his
previous posting that the fits are not stable for high mx values (signal
and peaking background are swapped), and are not good for intermediate
mx values. Grouping several high mx bins seems not to give more stable
results.
Another possibility (which can also be applied when constraining S/P =
signal/peaking on data) is to determine separately S and P, by e.g.
counting or fitting for S in events with truebrecomode==recobrecomode,
and fitting ony P and the combinatorial background in events with
truebrecomode!=recobrecomode. This latter solution should give more
robust estimates.
In any case, any S/P constraint would be determined on the entire
(charged+neutral B) sample, and it should be dependent perhaps only on
the kinematical variables.
Any comments?
Ciao, Concezio.
Antonio Petrella wrote:
> Hi,
>
> we also computed a correction factor for the signal/peaking bkg using
> the entire mx distribution, not a bin by bin.
>
> In this case the fit looks better, with respect to the bin by bin one:
>
> http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fix129/test_fix129fitresults.eps
>
> http://www.slac.stanford.edu/~petrella/tmp/scra/Ibutest_fixed/test_fixedfitresults.eps
>
>
> cheers,
> Antonio
|