Hi Rich,

well spotted. As Nick has pointed out a long time ago, the LCIO  
document is inconsistent and the d0 sign is wrong.
At least in eq. 3 if that's what you mean. That's one reason why I  
have linked the L3 note in our javadoc and not the LCIO doc, yet. If  
there's an updated version, we should link that, of course.
I have written up the track parameters in org.lcsim, which are also  
what I think the real LCIO parameters are, in contrib/JanStrube/ 
vertexing/vertexing.pdf.
This is just a draft, but very detailed, and it underlies the  
conventions that are used in HelixSwimmer and everything else I am  
working on.

Cheers,
     Jan


On Nov 27, 2007, at 6:36 PM, Richard Partridge wrote:

> Hi Rob,
>
> It looks to me like the note on the helix parameter convention  
> differs from
> my understanding of what we have previously agreed on.  Namely, I  
> believe
> the sign of d0 is opposite to the "L3 convention".  There is a link  
> to the
> note describing this in the getTrackParameters method for the track
> interface javadocs:
>
> "getTrackParameter(int i)
>           Get an individual track parameter The track parameters  
> for LCD are
> defined as follows IndexMeaning 0 d0 = XY impact parameter 1 phi0 2  
> omega =
> 1/curv.radius (negative for negative tracks) 3 z0 = z of track  
> origin (z
> impact parameter) 4 s = tan lambda Parameters according to the L3
> conventions"
>
> There is a link to
> http://www.lcsim.org/software/lcsim/apidocs/org/lcsim/util/swim/doc- 
> files/L3
> _helix.pdf in the text L3 conventions.
>
> I don't particularly care what convention we use as long as we are
> consistent.  So far, I think we follow the L3 convention, and not  
> the LCIO
> doc you found.
>
> Rich
>
> -----Original Message-----
> From: [log in to unmask]
> [mailto:[log in to unmask]] On Behalf Of Robert  
> Kutschke
> Sent: Tuesday, November 27, 2007 6:20 PM
> To: [log in to unmask]
> Subject: Revised notes now on the wiki
>
> Hi All,
>
>    I have revised the notes that I sent around earlier.  They are  
> now on the
> wiki:
>
> https://confluence.slac.stanford.edu/display/ilc/FastMC+Track 
> +Discussion
>
> The main changes are:
>    1) Added Caroline's comments.
>    2) Added a link to the official LCIO document that defines the  
> track
> parameters
>        and the reference point.
>    3) Added a link to the definition of what is in the persistent
> representation.
>    4) Changed point 2 and 3 to better represent what we said.
>
>      Rob
>
>