Hoi Ric,

I realized  one drawback  (for b->s gamma,  not us): Filtering  on the
tagbits precludes  dumping all true  signal events.  This was  a point
specifically raised by Henning. Is  there the possibility to filter on
the truth block?

Of course we  can skip the tagfilter business  and just save diskspace
by dumping events with either
   
   reco'ed lepton or photon 
   true b -> s gamma
   true b->u l nu (?)

I am  not 100% familiar with  the terminology of  "PID weighting", but
even PID killing is fine as long as we have data/MC PidTables.

Another drawback is brem recovery if the cut-off is high.  But I think
the diskspace gains would be  high enough even when requiring a lepton
with p*>0.5GeV (i.e. effectively the same cutoff as now).

Cheers,
--U.


Riccardo Faccini writes:
 > Hi Everybody,
 > regardless of the availability or not of the hbook disk space, I think we
 > need to seriously consider the option of saving only events with an
 > energetic lepton or photon. I would also consider applying a purity cut
 > (looser than the final one) at the ntuple generation level.
 > 
 > I would say that, assuming we use PID weighting for PID systematics, the
 > semileptonic and b->s gamma analyses would not be affected.
 > 
 > While I test the filter to do this, does anybody see any drawback on such
 > a decision?
 > 	ciao
 > 	ric
 >