Difference between revisions of "G2p Analysis Minutes"
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| + | ==2/12/2014== | ||
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| + | Present: Chao, Jixie, Jie, JP, Min, Melissa <br> | ||
| + | By Phone: Toby, Ryan, Ellie, Karl, Pengjia<br> | ||
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| + | '''Feature Presentations:''' | ||
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| + | *Melissa: | ||
| + | **Showed a summary of checks she's done to try to understand the discrepancy in yields for packing fraction runs. Many different tests were <br>done testing the cuts (acceptance, PID and raster) as well as checking the multitrack efficiency and comparing the first and second half of each run.<br> JP pointed out a few odd things that should be resolved (such as the "spikes" in the reconstructed phi variable, events above the good electrons in <br>leadglass 2D plot, etc.) The difference in yields is still not clear, but it's possible that a Moller measurement that was taken between runs 3503 and <br>3574 could have altered the beam conditions. She will discuss with Pengjia to see if the Moller measurement had a large effect on beam position. <br> More details can be seen in her slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/melissac/Elastic/Elastic_2_12.pdf here]. | ||
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| + | *Min: | ||
| + | **Showed an update on her pointing study to determine the central scattering angle. She showed the details of calculating the uncertainty in the <br>scattering angle using survey results. She used the assumption that z and x are the same for both theta1 and theta2, which JP warned could in be <br>incorrect. Looking at the results for the left and right HRS, the results from pointing and survey agree for the LHRS, but not for the RHRS. The pointing<br>uncertainty is different for left and right HRS; this is determined using the difference in the carbon ground state and first excited state, compared to<br> the nominal value. Min is currently writing up the details of the pointing study so far. More details can be seen in her slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/mhuang/02122014/02122014.pdf here]. | ||
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| + | *Pengjia: | ||
| + | **Gave an update on the status of BPM calibrations. He is working on the calibration for the optics run near 3185, but unfortunately there are no straight <br>through calibrations with div=2. The closest calibration is from 3/6 with div=3. Looking at the results for run 3185 using this calibration gives a beam <br>position of -0.84mm(X) and 2.39mm(Y) at the target. Chao's fitting result for this run was -3.5mm(X). JP asked how much a change in beam position of <br>3mm would affect the central angle calibration. Pengjia will try to get the calibration as good as possible, then summarize his work and determine the <br>uncertainty for the beam position. Also, he will compile a table of all beam condition changed throughout the run. His slides can be seen [http://hallaweb.jlab.org/experiment/g2p/collaborators/pzhu/02122014/bpm_status_20140212.pdf here]. | ||
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==2/05/2014== | ==2/05/2014== | ||
Revision as of 19:25, 12 February 2014
Minutes of the weekly analysis meetings
Contents
2/12/2014
Present: Chao, Jixie, Jie, JP, Min, Melissa
By Phone: Toby, Ryan, Ellie, Karl, Pengjia
Feature Presentations:
- Melissa:
- Showed a summary of checks she's done to try to understand the discrepancy in yields for packing fraction runs. Many different tests were
done testing the cuts (acceptance, PID and raster) as well as checking the multitrack efficiency and comparing the first and second half of each run.
JP pointed out a few odd things that should be resolved (such as the "spikes" in the reconstructed phi variable, events above the good electrons in
leadglass 2D plot, etc.) The difference in yields is still not clear, but it's possible that a Moller measurement that was taken between runs 3503 and
3574 could have altered the beam conditions. She will discuss with Pengjia to see if the Moller measurement had a large effect on beam position.
More details can be seen in her slides here.
- Showed a summary of checks she's done to try to understand the discrepancy in yields for packing fraction runs. Many different tests were
- Min:
- Showed an update on her pointing study to determine the central scattering angle. She showed the details of calculating the uncertainty in the
scattering angle using survey results. She used the assumption that z and x are the same for both theta1 and theta2, which JP warned could in be
incorrect. Looking at the results for the left and right HRS, the results from pointing and survey agree for the LHRS, but not for the RHRS. The pointing
uncertainty is different for left and right HRS; this is determined using the difference in the carbon ground state and first excited state, compared to
the nominal value. Min is currently writing up the details of the pointing study so far. More details can be seen in her slides here.
- Showed an update on her pointing study to determine the central scattering angle. She showed the details of calculating the uncertainty in the
- Pengjia:
- Gave an update on the status of BPM calibrations. He is working on the calibration for the optics run near 3185, but unfortunately there are no straight
through calibrations with div=2. The closest calibration is from 3/6 with div=3. Looking at the results for run 3185 using this calibration gives a beam
position of -0.84mm(X) and 2.39mm(Y) at the target. Chao's fitting result for this run was -3.5mm(X). JP asked how much a change in beam position of
3mm would affect the central angle calibration. Pengjia will try to get the calibration as good as possible, then summarize his work and determine the
uncertainty for the beam position. Also, he will compile a table of all beam condition changed throughout the run. His slides can be seen here.
- Gave an update on the status of BPM calibrations. He is working on the calibration for the optics run near 3185, but unfortunately there are no straight
2/05/2014
Present: Kalyan, JP, Chao, Jie, Min, Jixie, Melissa
By Phone: Toby, Ryan, Ellie
Feature Presentations:
- Toby:
- Working on dilution analysis. Gave an explanation of his method to determine the background yield in terms of the dilution runs (carbon,
empty, dummy). He also needed to create a scaling factor to relate the carbon runs to the nitrogen background. Using Moshe's nitrogen
simulation he was able to scale the carbon production data (with the "empty" run yield subtracted out) to match the nitrogen yield. He made
a graphical cut on the carbon and empty dilution to isolate the elastic/quasi-elastic channels so that each channel could be scaled separately.
He can then use these scaling factors to determine the overall background yield. The current scaling factors result in a background contribution
that is much too large; the yield is greater than the yield for a production run. This is most likely due to the fact that Toby currently doesn't
include any radiative corrections, which he will include in his method for next time. The details of his method can be seen in his slides here.
- Working on dilution analysis. Gave an explanation of his method to determine the background yield in terms of the dilution runs (carbon,
- Chao:
- Gave an update on the status of optics calibrations. He is currently working on longitudinal optics for the 2.2 GeV, 5T setting, since Min will
need this for her pointing study. He first used a simulation to show the effect of the longitudinal field, setting the beam position to the average
value of the BPM readout. The beam positions actually vary slightly between different optics runs, so he had to approximate the beam position for
"bunches" of 5000 events. An event by event simulation was used to calculate the effective theta and phi angle. The calibration looks pretty good
for this setting. The calibration tool kit, which combines the optimizer and the simulation, is almost finalized. He is currently working on updating
the reconstruction script to calculate the kinematic variables. More details can be seen in Chao's slides here.
- Gave an update on the status of optics calibrations. He is currently working on longitudinal optics for the 2.2 GeV, 5T setting, since Min will
- Jie:
- Working on updating the simulation package to include radiative corrections. There are two pieces to the correction; the radiation effect and the
straggling effect. The radiation effect includes the contribution from the dynamical effect (Bremstrahlung), which Jie has approximated as two
external radiator lengths. Ryan suggested just doing the full internal calculation, as it doesn't require much extra computing power. Since our target
thickness is ~0.03, the straggling effect is significant. He showed the simulated yields for the elastic nitrogen peak with and without the radiative
corrections, but neglected to include the radiative tail, which he will include this for next time. He also looked at the simulated yields using the actual
beam positions for the packing fraction runs 3503, 3574 and 3864. The yields agree within 4.5%, meaning that the differences in beam position is not
what is causing the discrepancy in the yields of the packing fraction runs. Jie's slides can be seen here.
- Working on updating the simulation package to include radiative corrections. There are two pieces to the correction; the radiation effect and the
1/24/2014
Present: Kalyan, JP, Chao, Jie, Min, Melissa
By Phone: Toby, Ryan, Karl, Pengjia
Feature Presentations:
- Melissa:
- Gave an update on packing fraction analysis. Compared the x/y beam positions for the four packing fraction runs for material 7; one
run (3727) has unreliable beam position information, but the other 3 runs seem fairly consistent. There is still a large discrepancy in the
yield for one run (3503). This is the earliest run taken; she will go through the logbook to look for any condition changes that could cause
this discrepancy. The results for the packing fraction for the other 3 runs seem fairly consistent, but lower than expected. More details can
be seen here.
- Gave an update on packing fraction analysis. Compared the x/y beam positions for the four packing fraction runs for material 7; one
- Pengjia:
- Gave an overview of his calibration method; the raw signal received in the antenna is compared to the recorded ADC value, and the
linear region is fit. This can then be rewritten using a diff/sum value and the nonlinearity corrected for. The position is then calibrated
using data from harp scans. Some of the calibrations were used for runs with different currents, assuming that the beam position
didn't change for these runs, which JP suggested was a dangerous assumption to make. There were several periods where the pedestal
was different between the calibration and production runs. This fluctuating pedestal could change the resulting beam position by ~2mm.
For next time, Pengjia will summarize the assumptions made for these calibrations so the uncertainty can be assessed for each one. More
details of his calibration method can be seen in his slides here.
- Gave an overview of his calibration method; the raw signal received in the antenna is compared to the recorded ADC value, and the
- Min:
- Gave an update on the pointing study to determine the central scattering angle. She showed the equation for elastic scattering
(which includes energy loss); she will look at the difference in the scattered energy for two different nuclei. She included two different
methods for calculating the pointing uncertainty. The first method uses the carbon-12 ground state and first excited state, and gave
a result for d-theta/theta <1%. JP suggested Min will probably need to combine left and right data to get the precision we need. The
second method combines various uncertainties (from survey, beam_x, etc.) and uses 2 different scattering angles; one including the
z-offset and one without. Using just one scattering angle to compute d-theta gives an uncertainty of ~2mr, using the quotient of the
two scattering angles gives an uncertainty of ~0.2mr, and using the difference of the two angles gives an uncertainty of ~0.04mr. She
still needs to include input for the incoming beam angle, and include the uncertainty from energy loss. More details can be seen in her
slides here.
- Gave an update on the pointing study to determine the central scattering angle. She showed the equation for elastic scattering
General Discussion:
- Ryan:
- Working through Rosetail to understand radiative correction calculations/code.
- Toby:
- Looking at scaling carbon data to nitrogen for dilution analysis.
- Chao:
- Working on longitudinal optics calibration.
1/15/2014
Present: Kalyan, Chao, Jie, Min, JP, Jixie, Melissa
By Phone: Ellie, Toby, Ryan, Karl, Alexandre, Pengjia
Feature Presentations:
- Jie:
- Gave an update on using the simulation package to determine the packing fraction. He showed multiple methods for extracting
the packing fraction, which account for different contributions to the overall yield. He used the g2psim package to get relative cross
sections for each contributing material. Next he will work on including the radiative corrections to the elastic peak and include the
calibrated beam position information (once it is ready). Details for the methods used can be seen is his slides here.
- Gave an update on using the simulation package to determine the packing fraction. He showed multiple methods for extracting
1/8/2014
Present: Kalyan, Chao, Jie, Min, Melissa
By Phone: Ellie, Toby, Ryan, Karl, Alexandre, Pengjia
Feature Presentations:
- Melissa:
- Gave a short update on yields for packing fraction runs. For one run (3864), the ungated livetime is significantly different then
the helicity-gated livetime. Using the average of the helicity gated LT values for the normalization makes this run agree better with
other packing fraction runs (3574 and 3727). She will check the beam position for these runs to see if this could have a large effect
on the yields. Her slides can be seen here.
- Gave a short update on yields for packing fraction runs. For one run (3864), the ungated livetime is significantly different then
- Chao
- Gave an update on the simulation package. Previously, the real theta and phi were not determined event by event, but for an entire
run. Since we know the position of the reaction point and the sieve hole, and the momentum of the electron, it is possible to use a
bisection method to determine the real theta and phi for each event. With this update it will be easier to determine the calibration for
different dp settings. Next he will work on finishing the optics calibration for the first setting with the target field. His slides can be
seen here.
- Gave an update on the simulation package. Previously, the real theta and phi were not determined event by event, but for an entire
- Min
- Gave an update on pointing analysis. The calculation was done using the March 14th calibration, using a carbon foil in liquid helium.
Using the carbon-12 ground state and first excited state to do the calibration of d(delta-E'), the results for the LHRS (4.40MeV) and
RHRS (4.42 MeV) agreed within the uncertainty with the nominal value (4.44MeV). However, including other uncertainties (survey and
beam x), add up to ~0.11 deg uncertainty in the scattering angle. She concluded that using the carbon foil in LHe is not ideal for a
pointing study. Next she will try CH2 run in longitudinal target field setting, once the optics calibration is complete for this setting. Her
slides can be seen here.
- Gave an update on pointing analysis. The calculation was done using the March 14th calibration, using a carbon foil in liquid helium.
- Pengjia
- Gave an update on the status of the BPM calibrations. He has finalized the calibrations for data taken from April 11th to May 18th,
which includes three different BPM gain settings. For settings before April 11th, the process is more complicated (larger pedestals,
auto-gain), but he will try to finalize the calibrations soon. He will provide a technote of his procedures and results. More details can
be seen here.
- Gave an update on the status of the BPM calibrations. He has finalized the calibrations for data taken from April 11th to May 18th,
General Discussion:
- If any students are interested in giving a talk at the APS April Meeting, please circulate an abstract to the group. The deadline for abstract submission is this Friday, January 10th.
