Hi Kerstin,

> >     What are the cuts on the momentum/energy of charged
> >     and neutral particles in the recoil?
> We have a table in the next version of BAD 1212 that lists the selection 
> criteria. You can see it on page 6 of this unofficial version:
> It is the selection proposed in BAD 1111 (but we picked it up from the 
> BRecoilUser package, so we should not be affected by the typos in earlier 
> version of that BAD).
> >     The total charge distribution for the enriched sample
> >     of neutral B gets very asymmetric in data.  Is this a loss
> >     of negative slow pions in data due to interactions?
> Is there a reason why we would expect to lose negative slow pions with 
> higher probability than positive slow pions? 

The cross section for low energy pions with nucleons is different 
for pi- and pi+ due to the different combination of isospin states.

That is in particular relevant if the energy corresponds to an 
excitation of a Delta resonance (pi N -> Delta -> pi N).

E.g. at T_kin(pi)=195 MeV: sigma(pi+p)>>sigma(pi-p). 
For small pion energies:   sigma(pi+p)< sigma(pi-p).


> And if so, would we think that for the charged B, the asymmetry is from 
> slow pions that come from fragmentation processes or such (not from D* and 
> so they would be in both B charge samples)?
> Spontaneously, I don't have an idea how we could test this easily.
> Shouldn't this be something we should know from the B0->D*lnu analyses?
> >     the effect is much smaller in the charged B, for which
> >     you do not apply the D* l nu veto.
> >   - have you tried to change the purity of the Breco selection,
> >     to see whether this might cause problems?
> We have changed purity cuts earlier in the analysis, but not recently,
> so we have not tried looking at this in this context. We could try this.
> >     or enlarge the q2 cut on the recoil?
> Do you mean q2 = the invariant mass of the W? We do not apply any cut on 
> q2. So are you suggesting we should try cutting on it?
> >   - Do you understand the large change in charged multiplicity between
> >     enriched and depleted samples?  The neutral multiplicity increases
> >     for the enriched samples, the charged multiplicity decreases.
> >     Does this point to problems with the enriched MC?  Jet-set
> >     fragmentation?
> Are you looking at the background subtracted spectra or the spectra before 
> background subtraction? I am not quite sure, but I think the trend is 
> similar whether or not we look before or after background subtraction.
> I guess in the neutrals it could be JetSet fragmentation. Backgrounds from 
> the detector should also show up in the depleted sample.
> Not sure how we could test this easily.
> >   - the enriched Emiss-Pmiss and MM*2 distributions do not
> >     show the expected peaks. Emiss-Pmiss= MM2/(Emiss+Pmiss) assumes
> >     a linear dependence of the MM2 resolution on Emiss.
> For Emiss-pmiss I think it is fair to look at this after the mm2 cut (as 
> we tend to think of the mm2 cut as cut to suppress background and 
> Emiss-pmiss to then improve the mX resolution). The enriched sample then 
> shows a good peak, the depleted is not so great.
> >     Have you checked MM2 vs Emiss?
> Not on release 18. But we have studies we performed on release 14, which 
> you can find here:
> It does not have mm2 vs Emiss, though, but a bunch of other plots related 
> to the neutrino (and also other things, resolution and truth matching 
> studies). We could check mm2 vs. Emiss on the current ntuples.
> >     I do not understand the motivation of the additional
> >     cut on the MM^2.
> It's really more the Emiss-pmiss cut which is additional. The mm2 cut 
> removes a lot of charm background at low mX (the long positive shoulder in 
> the enriched sample). We showed this at the June CM:
> Basically, mm2 suppresses charm background, Emiss-pmiss improves mX 
> resolution. Kinematically it makes sense when you consider what losing a 
> kaon does to these distributions.
> >   - Have you tried to look at these distribution with fewer bins
> >     on Mx?
> I am not sure I understand the question. Do you mean whether we have 
> performed data-MC comparisons for a restricted range of mX? We have not 
> tried that, since we are using the full range for the unfolding. But maybe 
> we could learn from making the comparisons in the low mX only, as we would 
> change the S/B significantly. Is that what you are thinking of?
> Kerstin
> > So many questions, no clear answers?
> > Ciao,
> > Vera
> > -----Original Message-----
> > From: [log in to unmask] [mailto:[log in to unmask]] On Behalf Of Kerstin Tackmann
> > Sent: Friday, August 31, 2007 2:26 PM
> > To: vub-recoil
> > Subject: Data-MC Agreement (again)
> >
> >
> > Dear vub-recoilers,
> >
> > as you probably know, we are seeing some problems in the data-MC
> > agreement. The most recent plots are here:
> >
> >
> > We obtain these plots as follows:
> > *Remove the cut on the given variable from the analysis.
> > *Perform the fit to the mX spectrum with this selection.
> > *Rebin the data and MC in the variable under study and use
> >  the *comp from the previous fit to mX to scale the MC
> >  components.
> >
> > The main concern is about the neutrino variables and Qtot.
> >
> > If we could have plots using this technique for the Vub analysis, that
> > would be a very interesting comparison, from which we could hopefully
> > learn and which would help us a lot in the review. I would really
> > appreciate if someone could look into this (as soon as possible)
> > -- please let me know if that would be possible. I'd be happy to give
> > more technical details, just let me know if something isn't quite clear!
> >
> > Thanks so much,
> > Kerstin
> >
> >
> >