Hi,

 another check to study the non-resonant background events for rho/omegalnu

 These are the invariant masses of the Xu system for the nonresonant MC. I
did the plots in two cases that are interesting here.

 - Xu decays in 2 charged pions
 - Xu decays in 2 charged pions + other stuff(not charged pions)

 here they are

 Xu -> 2 charged pions
 http://www.slac.stanford.edu/~daniele/exclvub/2pi.eps

 Xu -> 2 charged pions + other stuff(not charged pions)
 http://www.slac.stanford.edu/~daniele/exclvub/2pim.eps

 These plots show the reason why rholnu is much more affected by the
addition of nonres MC below 1.2GeV while the omegalnu is not. The cut on
deltam<.1GeV should select basically events with two charged pions and
nothing else. Their invariant mass is going to peak around the rho mass
(as shown by the first plot). On the other hand if other particles are
present (deltam>.1GeV) the invariant mass is far from the omega mass.


 Daniele





On Mon, 9 Jun 2003, Daniele del Re wrote:

>
> Hi all,
>
>
>  I studied a bit more in detail the problem of the vub reweighting in
> the exclusive analyses.
>
>  First, these are the mx plots for the generic MC hybrid and for the
> reweighted one
>
>  Gene MC
>  http://www.slac.stanford.edu/~daniele/exclvub/ometest3both.eps
>
>  Our rew
>  http://www.slac.stanford.edu/~daniele/exclvub/ometestboth.eps
>
>  Blue is non-res and red is resonant.
>
>
>  Looking at the integral after reweighting we have the following:
>
>  http://www.slac.stanford.edu/~daniele/exclvub/ometestintegrals.eps
>
>  and the region around .7 GeV is very badly reproduced. This imply that we
> have to redo the reweighting with a finer binning is we want to use it
> also for the exclusive analyses (this does not imply that it will be
> possible).
>
>
>  Then I studied the non-resonant events that survive the cuts. Here
> I compare the hybrid MC with the pure non resonant one.
>
>
>  Rho:
>  ---
>
>  hybrid
>  http://www.slac.stanford.edu/BFROOT/www/Physics/Analysis/AWG/InclusiveSL/recoilXSL/plotrhotest/mxhadfit0-vubcomp.ps.gz
>
>  nonreso
>  http://www.slac.stanford.edu/BFROOT/www/Physics/Analysis/AWG/InclusiveSL/recoilXSL/plotrhotest2/mxhadfit0-vubcomp.ps.gz
>
>
>  Omega:
>  -----
>
>  hybrid
>  http://www.slac.stanford.edu/BFROOT/www/Physics/Analysis/AWG/InclusiveSL/recoilXSL/plotomegatest/mxhadfit0-vubcomp.ps.gz
>
>  nonreso
>  http://www.slac.stanford.edu/BFROOT/www/Physics/Analysis/AWG/InclusiveSL/recoilXSL/plotomegatest2/mxhadfit0-vubcomp.ps.gz
>
>  (white is signal and blue is vub background)
>
>  Consider that for the hybrid MC none of the vub background events is due
> to non-res decays.
>
>
>  Looking at these plots I see two major points:
>
>  - since the reweighting factor is ~1 below 1.2GeV you can imagine to add
> the hybrid and the non-res plots. This implies that the amout of
> non-resonant MC is huge after the cuts.
>
>  - the difference between rho and omega is clear. For the rho the non-res
> background is "peaking" around the rho mass while for the omega has
> basically  the same shape of the hybrid background. Then, once you
> switch from the old hybrid to our hybrid, you get a large difference for
> rho and negligible difference for omega (as shown in my plots today).
>
>
>  Then:
>
>  * we have to redo the rewegthing with bins around the rho/omega mass and
>    hope that the resulting non-res background will be small
>
>  * BTW, are we sure that such a reweighting (same integral for very low
>    masses) makes sense?
>
>  * in SP5 we have the new reweighting, correct? I think that people that
>    will do rholnu and omegalnu analyses will be not so happy about it...
>
>
>
>  Daniele
>
>
>
>
>