[Clas_cascades] Minutes April 7 2010

[Elton Smith]

Present: Elton, Hovanes, Stepan, Kijun
On the phone: Lewis<br>
Notes by Elton.

== Announcements==
# Hovanes has been elected chair of the Nuclear Physics Working Group.
Congratulations!
# Zhiwen was on shift.
# Discussed whether 10:00 am on Wed is a good meeting time. Despite the
lackluster attendance today, it was agreed to keep it at this time.

== Comments on Normalization Note ==
# [[Tagger multiple hit study]] Zhiwen and Lewis are checking the effect
of selecting multiple tagger hits on acceptance
# The present goal is to take all events. For events with more than one
photon, loop over all photons and chose the one that satisfies the missing
mass selection. Preliminary corrections to the cross section is given in
[[Multiple Hit CRS Difference]].
# Kijun: Why the correction is not constant with energy (Old black
triangles and new Red squares cross over). The g11 multi-photon correction
was energy independent. Elton noted that if only single photon events are
selected, the correction is indeed energy independent (depends only on the
rate of the tagger), however, if all events are selected, and the photon
is collected randomly, this might be energy-dependent.
# Hovanes: The correction looks like it is much larger than 10%. Lewis
said that he was unsure if he was using the same code for the comparison.
For this purpose, it is important to start with the same code and only
compare the effect due to multiple hits.
# g11 Delta++ (Kijun). Has compared the correction or multiple hits for 4
GeV (same as previous g11 and gets about 18%), but for the 5 GeV data it
is smaller about 10%.
#* The accidental rate depends only on the range of tagger hits read out
and the luminosity. Double check that these are the same for the two data
sets.
#* Kijun also confirmed the +/- 1 ns tagger timing cut from g11 to be
about 6%. Note that eg3 had a +/-2ns timing cut, so that the efficiency
should be quite small.

== Comments on Phi-- Note ==
# Elton drafted response to many questions and placed document under cvs.
# Elton checked the trigger rates, which are summarized with some relevant
links at [[Comments on rate dependence of Lambda rates]].
#* Hovanes will check these numbers
# Hovanes is adding moe answers and making corrections to the response.
Will update the note and replace into CVS. By next week we should have
finalized all responses except for a few that might require some work.


== Next Meeting April 14, 10:00 am ==
# Check eg3 correction for multiple photons using the otherwise exact code
(Lewis).
# Update Delta produdction for both G11 and eg3 based on committee
comments.


Elton Smith
Jefferson Lab MS 12H5
12000 Jefferson Ave
Suite # 16
Newport News, VA 23606
elton at jlab.org
(757) 269-7625
(757) 269-6331 fax