Hi Urs,

> Why is the B0 default value higher  than what we had last week (BRBR =
> 0.0279 +- 0.0049)? Now it seems to be very close to 0.03.
>

non res MC vs hybrid MC produces this difference

> Why  the  variation by  150  MeV?  I thought  we  had  decided to  use
> something like 90 MeV?

in order to see the impact of this effect I used a large shift

>
> The scans assume the default to  be at 1.55, not your latest "optimal"
> value of 1.63, right?

yes but I just wanted to be consistent with the results of the last weeks

>
>
>  >  As you can notice, moving mb down and a up, fixs part of the discrepancy
>  > at low Mx low values.
>
> I would not say this (i.e. I disagree). In the DATA scans, compared to
> the default,  the diff  plots would indicate  that the lower  mb scans
> have  higher level  of disagreement.   The overall  shape seems  to be
> independent of the mb value.  The same  seems to be true for mb = 4.95
> (again,  from the diff  plots).  I  would conclude  from this  that we
> cannot measure mb competitively with this analysis.

I fully disagree. Generic MC is able to reproduce part of the problem. If
we are sensitive to this effect, we are able to measure it.

If you are talking about the errors in the diff plots, I agree that the
difference in quadrature is not optimal. We should finally figure
out the way to compute them correctly.

>
>  >  4) our measurement is so clean and we have so many events that we are
>  > sensitive to these theoretical parameters. We can start thinking about
>  > fitting a and mb.
>
> I think  before we do that,  we should understand the  reco level cuts
> and effects a bit better.
>
>
>  >  5) I am a bit less worried about this slope now
>
> I am a man of constant sorrow (as blind Richard Burnett would sing) ...

I am short of ideas now.

Our control samples work fine.

Data-MC comparisons are ok (except the one on the variable we use to
extract Vub)

Bchs work fine (except some disagreement at low values but I think this is
compatible with the theo systematics).

either new ideas or let's assign a new systematics or let's demonstrate
that what we are seeing is covered by the present systematics.


Daniele