Difference between revisions of "G2p Analysis Minutes"
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| + | ==2/11/2015== | ||
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| + | Present: Chao, Jie, Min, Melissa<br> | ||
| + | By Phone: Pengjia, Toby, Ryan, Ellie, Vince<br> | ||
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| + | '''Feature Presentations:''' | ||
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| + | *Toby | ||
| + | **Gave an update on dilution analysis. The dilution factor is define as one minus the ratio of background yield over<br>total yield. The background yield includes contributions from nitrogen, helium and the foil endcap on the target cell. <br>To extract the dilution factor he must tune the Bosted model (for helium and carbon) to match cross section data, <br>radiate the simulation results and take ratios to obtain necessary scaling constants, and then apply these scaling <br>constants to calculate the background yield. For tuning the Bosted model, he is currently using cross section data <br>from the UVa quasi-elastic database. The kinematics do not match ours exactly, but this will work until g2p cross <br>sections are available. He used a χ-squared minimization routine to determine the scaling factor for each kinematic. <br>He also showed the resulting cross sections ratios, which are used to determine the scaling factors α, β and γ.<br>Next he will apply the cross section ratios to yields from dilution runs to calculate the background yields and dilution <br>factor for the 2.2 GeV, 5T transverse setting, after which he will move on to other settings. More details can be seen <br>in his slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/toby/g2p%20meetings/dilution021015.pdf here]. | ||
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==2/4/2015== | ==2/4/2015== | ||
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'''General Discussion:''' | '''General Discussion:''' | ||
*Starting next week we will change the meeting start time to 9:30am. | *Starting next week we will change the meeting start time to 9:30am. | ||
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==1/28/2015== | ==1/28/2015== | ||
Revision as of 18:24, 11 February 2015
Minutes of the weekly analysis meetings
Contents
2/11/2015
Present: Chao, Jie, Min, Melissa
By Phone: Pengjia, Toby, Ryan, Ellie, Vince
Feature Presentations:
- Toby
- Gave an update on dilution analysis. The dilution factor is define as one minus the ratio of background yield over
total yield. The background yield includes contributions from nitrogen, helium and the foil endcap on the target cell.
To extract the dilution factor he must tune the Bosted model (for helium and carbon) to match cross section data,
radiate the simulation results and take ratios to obtain necessary scaling constants, and then apply these scaling
constants to calculate the background yield. For tuning the Bosted model, he is currently using cross section data
from the UVa quasi-elastic database. The kinematics do not match ours exactly, but this will work until g2p cross
sections are available. He used a χ-squared minimization routine to determine the scaling factor for each kinematic.
He also showed the resulting cross sections ratios, which are used to determine the scaling factors α, β and γ.
Next he will apply the cross section ratios to yields from dilution runs to calculate the background yields and dilution
factor for the 2.2 GeV, 5T transverse setting, after which he will move on to other settings. More details can be seen
in his slides here.
- Gave an update on dilution analysis. The dilution factor is define as one minus the ratio of background yield over
2/4/2015
Present: Chao, JP, Jie, Min, Melissa
By Phone: Toby, Ryan, Pengjia, Karl
Feature Presentations:
- Chao
- Gave a status update on optics analysis. For the 2.2 GeV, 5T settings (longitudinal and transverse) there was
limited optics data taken. Instead, the 1.7 GeV optics matrix matrix was used for this setting, with a 0th order
correction for the longitudinal setting, and a 1st order correction for the transverse setting. He showed the
longitudinal setting as an example, applying the 1.7 GeV matrix and including the 0th order correction to center
the sieve holes. JP commented that, if the offset is large, there may be higher order effects to consider. There
are no optics runs for the 3.3 GeV setting, so he plans to use g2psim to determine the optics matrix. He is
working on an optics technote, and a technote summarizing the last target field measurement. More details can
be seen in his slides here.
- Gave a status update on optics analysis. For the 2.2 GeV, 5T settings (longitudinal and transverse) there was
- Min
- Gave an update on her acceptance study. For this time, she improved the fitting at the virtual plane (for both
x/y and , and θ/φ) and projected the results onto the focal plane. The corrections on the forward transport
function were incorporated into g2psim. For the reverse transport function, the fit was done using all dp scan runs.
The simulation does not match with the data at the edges; this is due to the boundary conditions in the simulation.
Min will try expanding the boundary to see if it better matches the data. More details can be seen in her slides here.
- Gave an update on her acceptance study. For this time, she improved the fitting at the virtual plane (for both
- Melissa
- Updated the data quality check for the 2.2 GeV, 2.5T setting to include RHRS runs. In general the problem
settings on the RHRS are consistent with the LHRS. She also gave an update on the packing fraction analysis;
there was a problem in the previous definition of the packing fraction. The updated method requires some input
from cross section models. The resulting packing fraction is slightly larger than the result from the previous
method. Next she will work on extracting packing fraction values for other settings. More details can be seen
in her slides here.
- Updated the data quality check for the 2.2 GeV, 2.5T setting to include RHRS runs. In general the problem
- Jie
- Calculated the energy loss using two methods; using his energy loss model (Monte Carlo, step by step), and
using a radiated cross section model (from Stein). He used a fixed initial energy and fixed scattering angle for
a carbon target, and didn't apply any acceptance cuts. He compared the dp spectra for the two methods and
found that his energy loss model agrees well with the radiation model. Next he will work on a full simulation
for a beam dependence study (once the acceptance is ready). More details can be seen here.
- Calculated the energy loss using two methods; using his energy loss model (Monte Carlo, step by step), and
General Discussion:
- Starting next week we will change the meeting start time to 9:30am.
1/28/2015
Present: Chao, JP, Jie, Melissa
By Phone: Vince, Ryan, Toby, Min, Pengjia, Ellie, Alexandre
Feature Presentations:
- Ryan
- Gave an update on data quality checks for the 1.1 GeV setting. He found that the spread in yields ranges
from 0.01% - 6.1%, with an average of ~2%. For this setting we also took runs on a short target cell (material
14). For settings with a large spread, there was a correlation between beam drift and yield drift. Overall, this
setting seems ok. Next he will move back to working on polarized radiative corrections. More details can be
in his slides here, and a detailed summary
of the data quality check can be seen here.
- Gave an update on data quality checks for the 1.1 GeV setting. He found that the spread in yields ranges
- Pengjia
- Gave an update on data quality checks for the 1.7 GeV setting. For settings with a large spread in yields,
he looked at the correlation with the calculated scattering angle. He found that in some cases the change in
yield was proportional to the change in scattering angle, but for some settings it was inverse proportional.
He also showed an example of a setting where the yield was drifting, but there was no change in the scattering
angle. He tried applying raster cuts to see the effect on the yield, but first needs to find a way to calculate the
charge while including the raster cut. There was some discussion how this could be done; it may be possible to
use the Happex DAQ, as it is triggered by helicity. More details can be seen in his slides here.
- Gave an update on data quality checks for the 1.7 GeV setting. For settings with a large spread in yields,
General Discussion:
- Toby will start replaying RHRS runs today, hopefully they will be done by the end of the week.
1/21/2015
Present: Jie, Min, Chao, JP, Kalyan, Melissa
By Phone: Pengjia, Vince, Ryan, Toby, Karl
Feature Presentations:
- Melissa
- Gave a summary of data quality checks for the 2.2 GeV, 2.5T, transverse setting. There are several momentum
settings with a significant spread (>2%) in the yields. In most cases, the spread in yields seems to be correlated
with a change in beam position, which often corresponds to beam down time during the run period. Examples of
problem settings can be seen in her slides here, and a summary of all settings is available here.
- Gave a summary of data quality checks for the 2.2 GeV, 2.5T, transverse setting. There are several momentum
- Chao
- Gave an update on the status of optics for the RHRS. For the longitudinal and transverse settings at 5T, only a
few optics runs were taken, so the plan is to use the 1.7 GeV optics matrix for these settings. He also included a
summary of the RMS value of each kinematic variable (δ, θ and φ) for each setting, and commented that
the RMS value for y_tg is around 3-4mm, but this is a rough estimation as the fitting is not as good for this variable.
Next he will test 2.5T transverse optics matrix on the 5T settings to see if it works. His slides are available here. - The simulation package has been updated to cover the RHRS and include some upstream geometries. The most
recent version of g2psim is available through github here: https://github.com/asymmetry/g2psim
- Gave an update on the status of optics for the RHRS. For the longitudinal and transverse settings at 5T, only a
- Min
- Gave an update on her acceptance study. For this time, she combined all dp scan runs in order to do the
corrections at the virtual plane, which was then projected onto the focal plane. The agreement at the virtual
plane looks good, but there is still some disagreement at the focal plane. Next she will fit the reverse transport
functions and compare target plane variables. More details are available in her slides here.
- Gave an update on her acceptance study. For this time, she combined all dp scan runs in order to do the
1/14/2015
Present: Chao, Jie, JP, Melissa
By Phone: Pengjia, Ryan, Toby, Ellie, Karl, Min, Vince, Alexandre
Feature Presentations:
- Jie
- Gave an update on the dp simulation, specifically trying to understand why the simulation result for elastic dp was
narrower than the data. Comparing the data (with just PID cuts) to the simulation result (using full acceptance, and
a raster diameter of 2cm), the simulation is narrower than the data. However, if he applies acceptance cuts to the data
and simulation, and uses a beam size of 4mm (which matches with the data), the results show a better match between
data and simulation. He also tried dividing the beam spot into 5 different zones, and looked at the resulting dp
distribution for each. He did see a shift in the central value of dp between zones, however this shift was not seen in the
simulation. He also compared the shift in θ and φ for the 5 zones. JP commented that the θ distribution in
the data is symmetric and centered around zero, while the simulation result is not. It is possible that this is due to the
fact that Jie is using the old SNAKE model; he will get the updated version from Min and see if it makes a difference.
More details can be see in his slides here.
- Gave an update on the dp simulation, specifically trying to understand why the simulation result for elastic dp was
- Pengjia
- Posted his false asymmetry results to the ELOG.
- Working on data quality check for the 1.7 GeV, 2.5T setting. It looks like the spread in yields in some settings is
strongly dependent on the scattering angle. JP suggested looking at beam position or other raw variables, since the
scattering angle is a calculated value and depends on optics. It seems most settings with problems correspond to a
break in time when the runs were taken, which may suggest a problem with the spectrometer. Pengjia will look into
this next. More details can be seen in his slides here.
- Toby
- Gave an update on his yield drift study for the 3.3 GeV setting. For this time, he looked at the target field (central
NMR value) over the 2.34 GeV momentum setting, a period of about 6 hours. While there are some jumps in the signal,
there isn't a consistent drift like is seen in the yields. However, there is a period where the signal jumps significantly; he
will look into a possible cause for this. He also looked at the scaler BCM counts and trigger rates for these runs. There
was no noticeable drift in the scaler rates, but the beam current was not stable during this time.. He also computed the
"scaler yield" by dividing the total triggers by the BCM counts and saw a drift similar to what is seen in the normalized
standard yield. Previous to these runs being taken, there was a flood in the hall resulting in a power outage. It's possible
that the drifting is a result of systems not being stable while these runs were taken. More details can be seen in his
slides here.
- Gave an update on his yield drift study for the 3.3 GeV setting. For this time, he looked at the target field (central
- Ryan
- Working on a data quality check for the 1.1 GeV, 2.5T setting. In general the setting looks pretty good; the maximum
spread is 10% and the minimum is 0.01%, with an average of ~2% spread. Fewer runs were taken in this setting, and the
runs were taken consecutively, resulting in smaller spreads overall. In addition, there was data taken at this setting at
3 different momentum settings, all looking at elastic, and all on the same material. Next he will try to determine the
problem for the settings with a large spread (~10%). More details can be seen in his slides here.
- Working on a data quality check for the 1.1 GeV, 2.5T setting. In general the setting looks pretty good; the maximum
1/7/2015
Present: Chao, Jie, JP, Min, Kalyan, Jixie, Melissa
By Phone: Yunxiu, Vince, Pengjia, Toby, Ryan, Ellie, Karl, Todd, Nilanga, Haiyan
Feature Presentations:
Each student gave a short update on their analysis projects since the last collaboration meeting on November 14th:
- Melissa
- Method for packing fraction analysis is complete; the packing fraction values for each material still need to be
extracted. This will probably take ~1 week, but the yield discrepancies need to be understood before it can be
completed. She is also working on data quality checks for yields, specifically the 2.2 GeV, 2.5T setting. After these
projects are complete she will work on the PbPt check using elastic asymmetries. More details can be seen in her
slides here.
- Method for packing fraction analysis is complete; the packing fraction values for each material still need to be
- Toby
- Focusing on data quality checks of yields for production runs. He has completed the 2.2 GeV 5T settings, both
longitudinal and transverse, and the 3.3 GeV setting. The 2.2 GeV 5T settings have few problems, but the 3.3 GeV
has many momentum settings where the yields drift over time. He sees a similar drift in the left and right arm data.
He is still trying to figure out the cause for the drift. In addition, he is working on tuning the Bosted model to helium
and carbon dilution runs to simulate the background for dilution analysis, with a goal of finishing the dilution analysis
by mid-march. More details can be seen in his slides here. - Information on data quality checks can be found on the wiki here.
- Focusing on data quality checks of yields for production runs. He has completed the 2.2 GeV 5T settings, both
- Jie
- Looked at the effect of changing the scattering angle on the cross section for carbon, nitrogen, helium and hydrogen.
This may help explain the discrepancy we see in the yields, but is problem not the only cause. He is also working on
finishing the dp simulation, which should be done soon, and will begin working with Min to learn more about the acceptance
study. More details can be seen in his slides here.
- Looked at the effect of changing the scattering angle on the cross section for carbon, nitrogen, helium and hydrogen.
- Chao
- Gave an update on the status of optics analysis. He is finishing up the 2nd iteration of the optics calibration; the LHRS
is complete and the RHRS has one setting to go (1.158 GeV). For the 2.2 GeV, 5T, transverse setting, there is no full
dp scan, so the longitudinal data taken at that energy setting will be used. Once the 2nd iteration of the calibration is
complete, he and Min will compile a technote on the optics study. He has also modified the geometry part of the g2psim
package to make it more configurable. More details can be seen in his slides here.
- Gave an update on the status of optics analysis. He is finishing up the 2nd iteration of the optics calibration; the LHRS
- Min
- Working on the acceptance study. In the focal plane, there seems to be good agreement between simulation and data.
In the target plane, in the θ vs φ plot, there seems to be a shift in φ for all dp settings; it seems to be a linear
correlation with dp. Next she will work on a correction for φ-target vs dp and compare target plane variables. To finish the
good septum, straight through setting it will probably take 1-2 months, then an additional 1-2 months for the other 2 septum
settings. More details can be see in her slides here.
- Working on the acceptance study. In the focal plane, there seems to be good agreement between simulation and data.
- Ryan
- He has completed a draft for a PRC paper on unpolarized He3 cross section data. He still needs to complete the He3 radiative
correction analysis for saGDH, but is waiting on updated nitrogen cross sections for saGDH. He is also working on the carbon/
nitrogen ratio for saGDH, but is waiting on updated analysis from Vince before continuing. He is also working on data quality
checks for production runs for the 1.1 GeV setting, and is starting to look into polarized radiative corrections. More details can
be seen in his slides here.
- He has completed a draft for a PRC paper on unpolarized He3 cross section data. He still needs to complete the He3 radiative
- Pengjia
- Calculated the false asymmetry by comparing the asymmetry before and after applying detector cuts. He found the false
asymmetry to be small; less than 200 ppm for all energy settings. He's also working on a data quality check for the 1.7 GeV
data set. More details can be seen in his slides here.
- Calculated the false asymmetry by comparing the asymmetry before and after applying detector cuts. He found the false
General Discussion:
- Yields stability/overall data quality check is the main issue at this time.
- Progress of acceptance study looks good, but could become an analysis bottleneck.
