Hoi,
the Fermi motion is parametrized with a function of the form
f(x) = N * (1-x)**a * e**((1+a)*x)
where x = kPlus/lambdaBar and lambdaBar = mB - mb. kPlus is in the
'events' tree. ~ursl/macros/FsxUtil/anaVub.cc::sfDependency() contains
my implementation (just in case ...). The default parameters in the
generation of the nres signal MC were
BMASS = 5.2792;
BQMASS = 4.800;
A0 = 1.29;
In the following eps files, the first page contains size plots:
Mxfit Mxgen
efficiency for Mxfit cut efficiency for Mxgen cut
f(kPlus) weights
The second page contains the relative error on the efficiency (NOT
Vub) for Mxfit (left) and Mxgen (right), fitted with a polynomial of
fourth order (or degree, I always forget).
mb = 4.800 +/- 90 MeV
---------------------
http://www.slac.stanford.edu/~ursl/talks/062002/sfDependency-0.09-0.00.eps
http://www.slac.stanford.edu/~ursl/talks/062002/sfError-0.09-0.00.eps
mb = 4.800 +/- 150 MeV
----------------------
http://www.slac.stanford.edu/~ursl/talks/062002/sfDependency-0.015-0.00.eps
http://www.slac.stanford.edu/~ursl/talks/062002/sfError-0.15-0.00.eps
a = 1.29 +/- 0.5
----------------
http://www.slac.stanford.edu/~ursl/talks/062002/sfDependency-0.00-0.50.eps
http://www.slac.stanford.edu/~ursl/talks/062002/sfError-0.00-0.50.eps
a = 1.29 +/- 1.0
----------------
http://www.slac.stanford.edu/~ursl/talks/062002/sfDependency-0.00-1.00.eps
http://www.slac.stanford.edu/~ursl/talks/062002/sfError-0.00-1.00.eps
Summary:
--------
o Sven's error is reproduced with the Mxgen cuts when varying mb by 150
MeV. (Remembering a factor of two.)
o Mxfit seems much less affected than Mxgen.
o 150 MeV as uncertainty on mb might be (or not) a sensible number.
Maybe 90 MeV is as good? Maybe we trust Uraltsev?
o Compared to the uncertainty in mb, the error from a is small. Again,
cutting on Mxfit seems to reduce the dependence on this parameter.
The interesting question to be settled: What uncertainties do we take?
Cheers,
--U.
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