G2p Analysis Minutes
From Hall A Wiki
Minutes of the weekly analysis meetings
Contents
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.
