Hello Vera,
On Tue, 4 Nov 2008, Luth, Vera G. wrote:
>
> Hello Everybody,
>
> I have been thinking about ways to enlarge the generic MC sample,
> without doubling the generic production.
>
> Should we consider a sample of BB events in which
> one B decays generically
> the second B decays semileptonically (all decay modes)
One issue I've with this proposal is that the Breco reconstruction depends
on the signal side, so this sample would be very similar to Breco
cocktail samples that we already have (and for which we can ask more MC).
The deadline to present our proposal has been moved to the end of the
week. Marcello and Roberto already provided estimates for the Vub
analysis and I'll do some work too. At this point we can have a discussion
next monday in the AWG meeting.
David
> This would allow us to check backgrounds from
> - all other semileptonic B decays
> - from the second B in the event, combinatorics,
> either Breco tagged analyses or untagged analyses.
>
> For one of our core analyses, B to D tau nu, the statistical errors
> of the MC are
> B+- B0
> PDF shape 11.5% 4.5%
> Constraints 4.2% 6.1%
> Total MC stat 12.2% 7.6%
> compared to total systematic errors of 15.6% and 9.4%.
> So, by more than doubling the MC sample, we could reduce this
> error by a factor of 1.5, in parallel to improvements in our
> understanding of the background modeling.
>
> Also analyses with semileptonic tags, the other B could serve for
> background assessment, for instance in b to s gamma and
> other rare decays.
>
> With 2x11% prompt semileptonic decays, plus 2x2.5% with tau decays,
> we could get a factor 4 for 500 million events generated.
>
> Another issue is, can we get more continuum MC, uds 2x for
> muon fake background, and may be also more ccbar since this gives
> real leptons.
>
> We are asked to make requests by tomorrow,
> Shouldn't we discuss this?
>
> Ciao
> Vera
>
>
>
> ============================================
> Vera Luth
> SLAC - Stanford University
> 2575 Sandhill Road, Menlo Park, CA 94025
> Phone: 650 926 2702 FAX 650 926 2657
> ============================================
>
> -----Original Message-----
> From: [log in to unmask] [mailto:[log in to unmask]] On Behalf Of Roberto Sacco
> Sent: Monday, November 03, 2008 8:34 AM
> To: vub-recoil
> Subject: generic samples + NO meeting tomorrow
>
> Dear all,
>
> we are not going to meet tomorrow, as we are still working on what was
> decided during the collaboration meeting.
>
> Regarding the generic MC samples, let me remind you that, in our
> published analysis, the uncertainty due to limited MC statistics is
> our second highest, at around 4%, depending on phase space cuts.
> Increasing the generic MC statistics by a factor 4 could bring this
> uncertainty down to about 2%. We expect the new mES fit uncertainty to
> be, too, at the 2% level. Would you agree with requesting a factor 4
> increase? Do we want more?
>
> Cheers,
>
> Roberto
>
>
>
