Weekly Minutes 2008-08-08
At JLab: Pawel Ambrozewicz, Ashot Gasparian, Mark Ito (chair), Subhash
Khanal, Yelena Prok
On phone: Dan Dale, Tulio Rodrigues, Dan Sober
See the [1]meeting page for the agenda.
Contents
* 1 GlueX Monte Carlo work
* 2 Collaboration Meeting
* 3 Paper Status Review
+ 3.1 Pion lifetime paper
+ 3.2 Photon flux paper
* 4 Compton Differential Cross Section
* 5 Next Secretary
GlueX Monte Carlo work
Work is progressing. Beni Zihlmann of Hall D is working on the geometry
for the lead tungstate insert. He has also implemented a scheme where
the list of particles, and their momenta, impinging on the front face
of the standard GlueX forward calorimeter are written to the Monte
Carlo output.
Collaboration Meeting
Again, no change in plans. Current thinking is to have the meeting in
the second part of September.
Paper Status Review
Pion lifetime paper
Dan D. and Aron are collaborating on a first draft. Outlines have been
exchanged. Dan presented [13]his outline and collected comments. Dan
and Aron will get together and sharpen the definition of their roles in
this effort.
Photon flux paper
Dan D. presented recent work by Alexei on a [15]comparison of
measurements versus simulation of the effect of the insertion of the
experimental target on the absolute tagging ratio for various photon
energies. The deviations are of order a percent. These are mainly a
validation of the pair production cross section included in GEANT and
are consistent with statements from the GEANT documentation; the
lifetime result depends only weakly on this agreement. Dan initiated a
discussion on whether it should be included in the paper. Dan will go
ahead and put it in, but its inclusion may be raised again later.
Compton Differential Cross Section
Pawel explained how we can take the angular distribution of Compton
events where we do not distinguish the electron from the photon (veto
not used) and convert that to a measurement of the photon angular
distribution, as is usually calculated in textbooks. See [17]his
webpage for the transformation formalism.
Next Secretary
Pawel will record the minutes next time.
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References
1. http://www.jlab.org/primex/wiki/index.php/PrimEx_Weekly_Meeting%2C_August_8%2C_2008
13. http://www.jlab.org/primex/weekly_meetings/slides_2008_08_08/physics_paper_toc_a.pdf
15. http://www.jlab.org/primex/weekly_meetings/slides_2008_08_08/abs_tag_R.pdf
17. http://www.jlab.org/primex/weekly_meetings/slides_2008_08_08/pawel/cdiff_csec.html