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Hi all,

 these are the very preliminary results of the study on the cut on deltaM.

 DeltaM is defined as the difference between the X system mass and
the mass obtained removing one pion with the right charge from the X
system itself.

 DeltaM = M(X) - M(X - 1 pion)

 Since we can have many pions with the correct charge I select the
combination with the minimum DeltaM.

 If the X system corresponds to a D* that decays in D0pi+ this DeltaM
should should be compatible with DeltaM = M(D*) - M(D0) = 0.145.

 I used the "old" production (I mean the one with the overlap bug we
started to run 10  days ago). The MC used is B0 cocktail and B+ cocktail
for the background and Vubmix+breco for the signal.


 These are the results.

 B0 cocktail
 -----------

 In

 http://www.slac.stanford.edu/~daniele/vub/deltamstudy/b0cocktail.ps

 you find

 TOP LEFT: DeltaM after the lepton cut for b->clnu events (with ntrk > 1)
 TOP RIGHT: same plot with zoom

 BOTTOM LEFT: DeltaM after all analysis cuts for b->clnu events (with ntrk > 1)
 BOTTOM RIGHT: same plot with zoom


 In

 http://www.slac.stanford.edu/~daniele/vub/deltamstudy/b0cocktail_MD0.ps

 you see the M(X - 1 pion) distribution

 TOP: lepton cuts
 BOTTOM: all cuts

 the D0 peak is clearly visible


 Finally in

 http://www.slac.stanford.edu/~daniele/vub/deltamstudy/b0cocktail_mx.ps

 you can see the Mx distribution for b->clnu events after all cuts (black)
and adding a cut on deltaM (.14<deltaM<.16).

 This cut is very good to reject Vcb events in the peak of the
distribution but less in the left tail. This makes sense since the events
at low Mx usually have either just one charged track or missed tracks.

 For the efficiencies see later.



 B+ cocktail
 -----------

 Same plots in

 http://www.slac.stanford.edu/~daniele/vub/deltamstudy/bpcocktail.ps
 http://www.slac.stanford.edu/~daniele/vub/deltamstudy/bpcocktail_MD0.ps
 http://www.slac.stanford.edu/~daniele/vub/deltamstudy/bpcocktail_mx.ps


 Signal
 ------

 Again same plots in

 http://www.slac.stanford.edu/~daniele/vub/deltamstudy/sigocktail.ps
 http://www.slac.stanford.edu/~daniele/vub/deltamstudy/sigocktail_MD0.ps
 http://www.slac.stanford.edu/~daniele/vub/deltamstudy/sigocktail_mx.ps


 Efficiencies (.14<deltaM<.16)
 ------------

 - B0 cocktail (b->clnu)

   Eps (no cut on MX) = 76%
   Eps (MX<1.6) ~90%


 - B+ cocktail (b->clnu)

   Eps (no cut on MX) = 97%
   Eps (MX<1.6) ~97%


 - Signal (b->ulnu)

   Eps (no cut on MX) = 98.4%
   Eps (MX<1.6) = 98.5%


 Conclusions:

 This cut seems to be useful for B0's even if it is less effective at low
Mx.
 I will try to investigate the possibility to apply a looser cut on delta
M (to include D** soft pions) and to study pions with the "wrong" charge.
I will try to perform a similar study removing pi0's and photons (for Bch)
even if it should be more challenging.


  Daniele