On Tue, 20 Feb 2001, Bjorn H Samset wrote:
>
> Ho :-) A quick reply before I have to run:
>
> > - Looking at Fig.4 in the report of Claus and Christian (AnNote#22),
> > one can see clearly that around the nominal intersection point
> > there is no significant dependence of Mcut on the vertex (all
> > histograms and curves are absolutely flat). Therefore, I would
> > expect that both centrality recipes (JH and NBI) should give
> > exactly the same results if a narrow cut is imposed on the vertex.
> > It would be therefore very nice if you could compare the results
> > (centrality dependence of dN/deta) using both methods under
> > (for example) a +-5cm vertex cut (statistics should be sufficient,
> > in my old analysis I even used +-3cm).
>
> Not if you look at their figure 5. There you can see that the different
> selections actually pick out different percentages of the total
> MinBias. The 0-6% cut in GetCentrality actually looks like it picks close
> to 10% of the events, even for a narrow vertex cut. Also the 0-50% cut
> only selects a total of 40% of the events. The NBI cuts also have a few
> similar problems, but not as severe. I do have enough statsitics to do the
> check you propose and I can check it pretty quickly once I can sit down
> with it (there's a lot going on this week, so I'm a bit stressed), but I
> really don't think that the results are comparable.
>
The bin size in Fig.4 and 5 is = 8cm.
I am talking about a narrow cut of +-5cm (or even +-3cm).
It is hard to believe that moving the vertex by 3cm could
change significantly the acceptance of the tiles.
JH or Hiro might have some numbers from GEANT simulations.
Fouad
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