[Frost] Z-Vertex w/ and w/o CLcut(10%)

[Michael Dugger]

Sung,

The vertex plots I showed are from my COBRA code, and that code had very 
bad numbers for the target and start counter positions. I am currently 
running the code with the proper g9a maps generated by Franz. This means 
that my previous COBRA stuff can not be trusted. I should have some new 
plots soon.

Your vertex plot looks nice. The terminology "upstream shifted" was meant 
to describe the z-vertex end points for the Butanol. From your plot, it 
looks like the 10%CL Butanol distribution starts at about -3.5 cm and ends 
at about 3.0 cm. Half a cm is probably not a huge problem but does point 
to an asymmetry in how events will be corrected in eloss. For forward 
going protons near the end caps, the downstream Butanol events will have 
less momentum corrections applied than upstream Butanol events. Making 
cuts interior to the Butanol would mitigate this, but it is a shame to 
have to do that when the vertex separation for p pi+ pi- is so nice!

Thanks for the info, and I'll let you know when I have new z-vertex plots.

Take care,
Michael

On Wed, 20 Oct 2010, Sungkyun Park wrote:

> Hi, Michael
>
> I made ZVertex plot with and without CLcut(10%).
>
> * 28 Runs in Period 7
> * Reaction: #gamma p -> p pi+ pi-
> * with and without 10% confidence level cut
> * angel is mad in Lab. System
>
> Plot:
> w/o CLcut :  http://www.jlab.org/Hall-B/secure/g9/sungkyun/IMG/Oct2010/ZVertex_Sit01_wo_CLcut0.1.gif
> w/ CLcut : http://www.jlab.org/Hall-B/secure/g9/sungkyun/IMG/Oct2010/ZVertex_Sit01_w_CLcut0.1.gif
>
> In plots, I can not find the exact effect about z-vertex "upstream" shifted.
>
> Sung
> Florida State University
>