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Vub measurement using recoil of fully reconstructed Bs

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Subject:
From:
Daniele del Re <[log in to unmask]>
Date:
05 Jul 2002 16:32:04 -0700 (PDT)Fri, 05 Jul 2002 16:32:04 -0700 (PDT)
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Hi,

 I tried to compute the systematics from the mes fit.

 First let me remind you how the fit is performed. After all cuts a fit to
the mes distribution for Mx<2.5 is performed with all parameter floating
in order to get the signal parameters. Then those parameters are fixed in
all the mes fit in each Mx bin.

 I repeated the fit varing those signal parameters within their error.

 This is the change in the fitted BRBR value:

* +1 sigma in mean gauss (cry ball)        +0.0  * 10^-3    (+0%)
* -1 sigma in mean gauss (cry ball)        +0.01 * 10^-3    (+0.6%)

* +1 sigma in sigma gauss (cry ball)       +0.20 * 10^-3    (+1.2%)
* -1 sigma in sigma gauss (cry ball)       -0.   * 10^-3

* +1 sigma in alpha param (cry. ball)      -0.50 * 10^-3    (-3%)
* -1 sigma in alpha param (cry. ball)      +0.48 * 10^-3    (+2.8%)

* +1 sigma in n param (cry. ball)          -0.30 * 10^-3    (-1.8%)
* -1 sigma in n param (cry. ball)          +0.88 * 10^-3    (+5.2%)

--------------------------------------------------------------------

      total  				   +1.02       +6%
        				   -0.58       -3.5%


 As a crosscheck I ran the fit leaving floating the cb parameters (alpha
and n) in each Mx bin fit.

 I got

 BRBR = 0.0178748 +- 0.00488316(stat) +- 0.00146808(MC stat)

 that is +5.8%, then is within the systematics.


 This numbers, together with the crystall ball vs gaussian fit
difference(1.2%), will give the systematics from the mes fit.

 +6.1%
 -3.7%

 We are also forgetting the error from the fit for Nsl. It has a stat
error of 1.6%.


 Daniele








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