G2p Analysis Minutes
From Hall A Wiki
Minutes of the weekly analysis meetings
Contents
7/8/2015
Present: JP, Min, Chao, Melissa
By Phone: Toby, Vince
Feature Presentations:
- Pengjia
- Working on comparing asymmetries determined from MAID to those calculated from
data; last time he showed a factor of 6 difference between the two results. This
time, he showed two different methods for calculating the differential XS from the
virtual photon XS. The first method calculates the differential XS directly from
the virtual photon XS, and the second method calculates the differential XS using
F1, F2, g1 and g2. He also showed two different methods for calculating the
asymmetry from the virtual photon XS; one method uses A1 and A2, while the other
is calculated from the virtual photon XS. There was a discrepancy between the two
methods, but he found that there was actually a mistake in one of the equations.
While the results from the two methods agree with each other, they are still a factor
of 6 larger than the results from data. More details can be seen in his slides here.
- Working on comparing asymmetries determined from MAID to those calculated from
- Toby
- Showed an update of his scattering angle study for model reconstruction. He is
using BPM and optics data to determine the scattering angle. He showed an example
of the calculated scattering angle; JP questioned whether the range was really from
0-16 deg. Toby pointed out that there really aren't many events at the boundaries,
the distribution is peaked between 4.5-9 deg. He then uses this scattering angle as
input for the Bosted model. At low ν the simulation results match reasonably well
with the data, but the discrepancy starts to become larger as ν increases. He took
a closer look at the reconstructed scattering angle for each central momentum, and
found that a second peak is visible for smaller values of p0. If this second peak was
real, the simulation should recreate the data, so this could suggest a problem with
the reconstruction. However, Chao pointed out that, for this energy setting, the optics
calibration is not complete (currently using the longitudinal optics matrix), so the
reconstructed θ and φ may not be correct yet. For next time, Toby will test this
analysis using the 1.7 GeV setting, which has calibrated optics. More details can
be seen in his slides here.
- Showed an update of his scattering angle study for model reconstruction. He is
- Melissa
- Gave a summary of packing fraction analysis. For some settings, the variation in the
yields (and Pf) is due to a fluctuation in the beam position. This will hopefully be
resolved by Jie's beam position/acceptance study. For the 2.2 GeV, 2.5T transverse setting
there is also an issue of a shift in ν between runs. For the 1.1 GeV, 2.5T transverse
setting, the yields vary depending on the beam current used for each run. JP suggested
a few things to check as the possible cause for these discrepancies including drift in the
BCM calibration, anneals of the target material, drift in field (HRS or septum), etc. She
has posted a technote draft here, feedback would be appreciated. More details can
be seen in her slides here.
- Gave a summary of packing fraction analysis. For some settings, the variation in the
- Min
- Gave an update on her acceptance study. Last time, she showed that the simulation results
are more narrow than the data. For this time, she tried cutting on just the center hole,
and found that the dp distribution from data better matched the simulation. JP suggested
cutting on each of the different holes individually to determine which hole causes the dp
distribution to be wider. More details can be seen in her slides here.
- Gave an update on her acceptance study. Last time, she showed that the simulation results
- Chao
- Gave an update on optics analysis, currently checking whether simulation results match
with data, starting with optics data. First he checked whether the geometry was correct,
some deviation was found in the recent optics meeting. The position of the BPMs is hard-
coded into the simulation, and the drifting algorithm is used to drift the electrons
backward to the BPMs to simulate the readout of BPM A and B. He compared the θ
distribution before drifting in the target field using a fixed and non-fixed BPM location.
The results using a fixed BPM match well with the data. He is currently working on
checking this for all momentum settings, and will follow up with Pengjia about the BPM
problem. More details can be seen in his slides here.
- Gave an update on optics analysis, currently checking whether simulation results match
7/1/2015
Present: Chao, Vince, Jie, JP, Min, Melissa
By Phone: Pengjia
Feature Presentations:
- Min
- Gave an update on acceptance studies. She showed a summary table of each energy
setting and septum configuration. There hasn't been any problems in the 2.2 GeV, 5T
longitudinal and 1.7 GeV, 2.5T transverse settings, but some settings (2.2 GeV, 2.5T
transverse, 1.2 GeV, 2.5T transverse and 2.2 GeV, 5T transverse) have a discrepancy
in the focal plane between data and simulation. She compared the data divided by the
Mott XS to the simulation results without XS, and found that the simulation results
of θ and φ are narrower then the data. JP commented that, while including the Mott
XS might change the shape of the distribution, it shouldn't change the boundary. She
work on figuring out the cause for this discrepancy before calculating the acceptance.
More details can be seen in her slides here.
- Gave an update on acceptance studies. She showed a summary table of each energy
- Pengjia
- Comparing asymmetries determined from the MAID model to those calculated from data.
Last time he showed a factor of 6 difference between the two results. He determined the
scattering angle and Q2 by fitting the data and compared them to the quantities calculated
from MAID. He also showed the results of calculating the quantities g1, g2, F1, F2, AL, AT,
dXSL, dXST, XStot andXSmott using MAID. He hasn't included radiative corrections in his
calculations, but this probably won't account for the factor of 6. More details can be seen
in his slides here.
- Comparing asymmetries determined from the MAID model to those calculated from data.
