[Clas_cascades] Minutes April 29

[Elton Smith]

Present: Elton, Hovanes (toward end of meeting), Stepan, Kijun
On the phone: Lewis, Ralf, Zhiwen, Haiyun <br>
Notes by Elton.

== Announcements==
# Haiyun will defend his thesis on Friday.
# Some confusion about the meeting start time due to a typo in previous
minutes. We reaffirmed the new day/time Thursday at 9:00 AM.

== Comments on Normalization Note ==
# Ralf summarized: Comparison between eg3 and g11 is within abou 20%, but
backgrounds due to high lying resonances have not been subtracted (nor
were they before).
# Note that there are some MM cuts on the data to enhance exclusivity, but
background still leaks through and this has not been corrected (in neither
eg3 nor g11 data)
# Elton: suggest to make the eg3/g11 comparison without this background
subtraction first, so that we can make a direct comparison between the new
multi-photon correction and previous comparisons.
# Haiyun mentioned that for his data set the feeddown from high lying
resonances into his data sample was about 10%.
# Ralf: Plan is to use 3pi background sample to estimate feedthrough into
exclusive sample. Subtraction may be guided by calculations.
# [[Multiple Hit CRS Update#New EG3 Compared to New G11 | Latest
comparison between eg3 and g11]]
#* G11 (blue) and EG3 (green). Comparison matches well up to 4.5 GeV.
Above 4.5 the comparison is within 20% but there could be some systematics
due to the trigger correction factor.
#* Ralf: Still need to look into the higher resonance background
subtraction which may energy dependent.
#* Kijun: Asked why the shape of the comparison between EG3 and G11 has
changed, if the correction should be independent of the beam energy.
#* Elton: The spectrum (uncorrected for multipler photons) could have
changed, since different photons can be chosen for the event.
#* Lewis: Multiple photons analysis: loop over all photons in the event
and pick the closest to the expected MM.

== Data vs simulation ==
# [[Eg3 simulation]]: Zhiwen. Changes made to wiki but forgot to commit
until recently
#* Kijun helped with simulations, but timing is still not completely
understood
#* Kijun: Removed trigger particle (pi-) from tcl file and this changed
results. Stepan claims this should only happen for electron runs. Photon
runs should ignore this flag and use the tagger instead.
#* Stepan: Need to determine whether the GSIM was processed as an electron
or photon run (Userana prints out run type)
#* Zhiwen: Acknowledges that treatment of trigger particle might not be
ideal, but should treat data and simulation in the same way. Once
understood these scripts can become standard for other eg3 studies.

== Comments on Phi-- Note ==
# Hovanes has updated the response draft on Sunday and checked it into
cvs.
#* Three plots still need to be produced and one systematic study (check
how the cuts were selected for the time difference between proton and
pion)
# Elton will take a look at the updated note.


== Next Meeting May 6, 9:00 am ==
# Phi-- response to committee
#* Check updated response (Elton)
#* Progress on remaining plots and systematic study (Hovanes).
# Normalization note (USC)
# Haiyun to give an update on thesis


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