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Re: updated talk for PID



Hall D PID Mail List:

On Tue, 25 Mar 2008, Matt wrote:

Dear Matt,

I have one remark below.

>
> Hi Eugene,
>
>
>
> > More PID will be most likely needed for non-overdefined reactions
> > (with a missing particle). It would be nice to get some idea from Matt,
> > how large the additional suppression should be.
> > I doubt that a 1C fit can sufficiently improve the PID.
> >
>
>
>     You're right that a 1C fit will definitely let in more background. As
> Alex has pointed out though, GlueX has been designed with excellent
> detection of neutrals in mind, so hopefully we rarely miss pi0's. As for the
> missing neutron, I would not be surprised if we do OK since it is hard to
> mess up pi's and nucleons and the missing neutron peak should be well
> separated.
>
>     The 1C fit studies are just one of a number of studies that we will need
> to do following the review. I would suggest a PID meeting dedicated to
> mapping out what studies need to be done to further investigate some of
> these numbers that we have come up with. It is obvious there are different
> camps regarding PID and we should work hard to come to some sort of
> convergence on how we approach this work. While it is always good to have
> cross checks, there's no sense in duplicate effort or bifurcating code.

I think cross checking always duplicates some effort.
Actually in HERMES we had a rule which I think was one of the best things
we ever invented. Every result which was supposed to be shown in public
needed a cross check with an independent code. both people had to analyse
the exact data or MC set and come to agreement on 1% level on track level.

A lot of bugs have been found like that. In some cases we even choosen
different methods to get a result and assigned the difference in results
as systematic error. Of course both methods had to be cross checked on track
level.

So I think some dublication is unavoidable to iron out all hick ups.
I actually thought it was nice to see that Eugene could reproduce your
results. Please don't take this remarks as any critism of your work, I
just wanted to point it out because it is important to me.

Cheers and have a nice day
elke




>
>    A few comments about the talk:
>
> Slide 17: I don't understand what you mean by 3C or 4C fits. There should be
> no point where you are performing a 3C fit on that reaction. Unless you are
> doing spatial vertexing?
>
> Slide 19: Similar comment. You are making a 3C fit and cutting at 1% and
> then making a 4C fit and cutting a 1%? Perhaps if I heard the talk it would
> make sense, but the slide on it's own is very confusing.
>
> Slide 20:
> 2nd main bullet - This can probably be reworded. "Additional methods of
> increasing..." or something like that.
>
> 3rd main bullet - If you feel it necessary to list the challenges in getting
> the kinematic fitter working, you should also mention that there is
> experience within the collaboration in overcoming these issues (Curtis, et
> al) and reference the successful kinematic fitter in use in CLAS analysis.
>
>
> --
> --
> ----------------------------
> Matt Bellis
> Carnegie Mellon University
> (office)  412-268-6949
> (cell)    412-310-4586
> ----------------------------
>

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