Hi Urs,
as we already discussed at the meeting there are probably two different
problems, the high momentum (un matched) SVT tracks and the theta=pi/2
problem.

I have just two warnings from past experiences with tracking:
	- don't forget to look at everything in terms of pt and not just
p, it can fake a lot of low angle effects.
	- forget about the chi^2 of the individual tracks, it has (or at
least, used to have) more problems than information

As far as the high mom SVT tracks I suggest to require that if pt>300MeV
we require >0 Dch hits. I have produced the corresponding root files and
will post the comparisons.

	ciao
	ric

>
> As already  mentioned by  Ric, there is  a non-negligible  fraction of
> SVT-only tracks with high momenta:
>
>   http://www.slac.stanford.edu/~ursl/talks/100202/momentum-svtonly.ps.gz
>
> Looking at the theta distribution of (nearly) all tracks,
>
>   http://www.slac.stanford.edu/~ursl/talks/100202/theta-all.ps.gz
>
> you can 'clearly'  see the problem if you know where  to look. To make
> it more obvious, now for SVT-only tracks with momentum <0.18 GeV:
>
>   theta:     http://www.slac.stanford.edu/~ursl/talks/100202/svt-only.ps.gz
>   dcaz:      http://www.slac.stanford.edu/~ursl/talks/100202/dcazPrimVtx.ps.gz
>   chi2/ndof: http://www.slac.stanford.edu/~ursl/talks/100202/chi2-ndof.ps.gz
>
> I don't know how to interpret the last plot, but the band at theta=1.5
> going down to 0 is from Svt-only tracks.
>
> If you require at least one DCH hist, all looks fine:
>
>     http://www.slac.stanford.edu/~ursl/talks/100202/with-dch.ps.gz
>
> I think it's time for a serious  study, and I'll do that over the next
> few days. It might affect a few things, though.
>
>
> Cheers,
> --U.
>