# Difference between revisions of "G2p Analysis Minutes"

Minutes of the weekly analysis meetings

## 8/17/2016

Present: Ryan, Toby, Ellie, Chao, Vince, Jie, Alexandre

Feature Presentations

• Ryan

Showed a comparison between asymmetries between LHRS and RHRS for the three 5T settings: 2.2 GeV long/trans and 3.3 trans. Overall there is good agreement between the HRS's, and the biggest disagreement is between the arms at the 2.2 GeV trans setting. Ryan will check that scattering angle dependence of the asymmetries next to see if this can improve the agreement. Currently the RHRS scattering angle reconstruction is not correct. Chao believes this is a coordinate system issue in his code.

• Chao

Back at JLab for one year. First thing he will focus on is correcting the scattering angle reconstruction for the RHRS replay. After this he will move onto the acceptance study for the 5T longitudinal setting.

• Jie

Working on understanding Pengjia's BPM code.

• Toby

Working on updating the target polarizations for the HRS's. Found a bug in his code in converting UNIX times. Also developing two parallel methods to determine packing fraction, one using fits and another using simulation.

## 8/03/2016

Present: Ryan, Toby, Karl, Vince, Jie, Alexandre

No Presentations.

• Jie

Got code for BPM calibration from Pengjia. Still waiting on some further explanation from Pengjia on the code. He will focus on the 5T settings first in the calibration

• Toby

Working on the g2psim package and using it for calculating the packing fraction. Replayed RHRS 5T transverse data, and according to Chao it should have final optics.

• Ryan

Has a working model dilution code.

## 7/27/2016

Present: Ryan, Toby, Jie, Vince, Kalyan, JP, Karl

Feature Presentations:

• Jie

Working on trying separate two peaks in the BPM pedestal runs. It does not appear that the two peaks can be filtered based upon the frequency using an FFT. Moving forward he will check how the double peaks affect BPM calibration uncertainty and check the BPM calibration procedure. More details can be found in his slides here

• Ryan

Presented raw asymmetries with three difference acceptance cuts to highlight the angle dependence on the asymmetry in the delta-region. Was able to produce a similar trend in models using scattering angles from the data. Going forward will try to find acceptance cuts that select similar numbers of events and see if the ratio between data points is the same as the ratio of model points to do a bin-centering type correction. More details can be found in his slides here

## 7/20/2016

Present: Ryan, Toby, Jie, Vince, Alexandre , Kalyan, Karl, Ellie

• Jie

Looking into 2-peak pedestal issue for the BPMs. Checking to see if the two peaks are at different frequencies and can be separated. If they cannot then the 2-peak pedestals will increase the BPM reconstruction uncertainty at the target to ~3-4mm (from 1-2mm) for runs with the double peak. Previously Pengjia did not consider any RMS value above 2000 in his analysis.

• Toby

Still working on getting the g2p simulation package to match g2p data. Able to now produce elastic peaks in the correct locations to match data. Requesting that someone familiar with g2psim make a post on the wiki detailing the variables in the output of the simulation root tree because they are not straight-forward to understand.

• Ryan

Completed setting up a python version of the radiated model code. Uses MAID/Hall B for the polarized and Bosted for the unpolarized. Does the unpolarized and polarized elastic tail but only uses RADCOR for the inelastic radiating.

## 7/13/2016

Present: Ryan, Toby, Jie, Vince, Alexandre , JP, Karl, Ellie

Feature Presentations:

• Jie

Showed a comparison between the BPM pedestals calculated during dedicated pedestal runs and during beam trips. The two methods agree, so Jie is moving forward with the beam trip method to fill in gaps for BPM pedestal calculations. His next step is to move onto checking the BPM calibration. More details can be found in his slides here

• Toby

Still working on getting the g2p simulation package to match g2p data. This will be used for calculating the packing fraction

• Ryan

Working on producing radiated models to compare to the g2p data.

## 7/6/2016

Present: Ryan, Jie, Kalyan, JP, Karl, Ellie

• Jie

Working on comparing pedestal values from dedicated pedestal runs and from beam-trip's. He's mostly found agreement and is working to settle the few outliers. After this he is moving onto to checking the BPM calibration.

• Ryan

Working on setting up radiated models to compare with the radiated data asymmetries.

## 6/29/2016

Present: Ryan, Toby, Jie, Vince, Kalyan, JP, Karl, Ellie

Feature Presentations:

• Jie

Gave an update on the BPM pedestal issues. In his slides he shows the pedestal histograms to demonstrate that the pedestal value is really shifting with time. Some pedestal's also exhibit a multi-peak structure, which ultimately will effect the uncertainty of the BPM calibration. He also showed the effect of using different BPM pedestal values for different runs and effects the BPM reconstruction. The resulting BPM position change is much larger than simulation would predict indicating that again that the BPM pedestal value is really changing with time. Going forward he will look to determine an accurate BPM uncertainty from the fluctuating pedestal values. More details on his slides can be seen here.

• Toby

Working on updating Melissa's packing fraction code to use simulation to match the quasi-elastic peak, instead of relying on fits because the packing fraction result is highly-sensitive to the fit parameters.

• Ryan

Working on raw asymmetries and comparing them with Toby to make sure they agree.

• Vince

Has updated ChiPT calculations that he will send out over the mailing list.

## 6/22/2016

Present: Alex, Ryan, Toby, Jie, Vince, Kalyan

Feature Presentations:

• Toby

Received Melissa's packing fraction code. Found that there is now a difference in the nu histograms for the elastic runs when compared to what Melissa used in her analysis. Melissa's tech-note shows only a single elastic peak, but new root-files have both a elastic nitrogen and helium peak. The two peaks are separated by about 5 MeV at E0 = 2.2 GeV. The existence of an additional peak effects the applicability of Melissa's fitting routines to these new root-files. Toby will contact Melissa and see what she can provide. Slides are here.

• Jie

Jie is still talking with Pengjia over the BPM pedestal issue. He hopes to have slides for next week's meeting.

• Ryan

Ed Folts confirmed the presence of helium bags in the septum bores and local dump box. In contact with Jessie Butler to find Ed's old pictures of the g2p target platform. Assuming helium is present in radiation thicknesses after scattering. Will update if there is any change. Tech-note with the radiation lengths can be found here

## 6/15/2016

Present: JP, Karl, Alex, Ryan, Toby, Chao, Jie, Vince, Ellie, Xiaochao, Kalyan

No presentations. Just verbal updated

• Jie

Jie gave a little more detail on the carbon cover from last week's slides. The carbon cover is a porous carbon sponge added to the BPM to help with radiation. This in itself shouldn't effect the pedestal but opening up the BPM to install it could have an effect. It's possible the pedestal change is also related to configuration changes in the target magnetic field. Jie will show more at meeting next week.

• Ryan

Confirmed from Chao that DP is not corrected for ELOSS. Still waiting to hear back from Ed Folts on g2p helium bags.

• Toby

Getting Melissa's packing fraction code this week. Will use it to update packing fraction calculations.

## 6/8/2016

Present: JP, Karl, Alex, Ryan, Toby, Chao, Jie, Vince, Ellie

Feature Presentations:

• Ryan

Gave an update on the radiation length calculation. He checked the energy loss calculation people did before and found out that we did not use the He bag during the experiment but before people built the He bag in the simulation. However the difference between He and air should not cause serious problem for us. More details can be seen in his slides here.

• Jie

Gave an update on the beam position problem. He worked together with Pengjia on this problem. The bpm database is updated so that the beam current dependence of the BPM is removed. Another problem is that the reported beam position would jump suddenly within the same momentum setting. Pengjia and he guess the pedestal of the BPM might be a possible reason. And between the two run they compared, a carbon cover was added which might influence the pedestal. So they did some study of the BPM pedestal values. The current cut Pengjia used before to select no-beam events is replaced by a more tight one. However, the results do not change much. More details can be seen in his slides here.

## 5/25/2016

Present: JP, Alex, Ryan, Toby, Chao, Jie, Vince, Ellie

Feature Presentations:

• Toby

Gave an update of his study on the scattering angle. The problem he mentioned on 5/11 has been solved. Both of the formulas are correct. However, he found that the central scattering angle jumped within one momentum setting for more than 3 deg. Chao mentioned that his calculation result does not show this behavior and they will discuss this offline. More details can be seen in his slides here.

## 5/18/2016

Present: JP, Karl, Alex, Ryan, Toby, Chao, Jie, Vince, Ellie

Feature Presentations:

• Chao

Gave an update of the acceptance study. He used the elastic scattering data to calibrate the resolution of the simulation. He found that the simulation package does not treat the resolution of the beam position properly. Thus the simulation package is updated to generate the events according to the beam profile. With this new update, the resolution of the simulation agrees with the data. More details can be seen in his slides here.

## 5/11/2016

Present: JP, Karl, Alex, Ryan, Toby, Jie, Vince, Ellie

Feature Presentations:

• Toby

Gave an update of the scattering angle calculation. He used two formulas from Pengjia and Chao to calculate the scattering angle and suggests that the results do not agree. People suggests that this two methods are equivalent and we should just use one of them. More details can be seen in his slides here.

• Ryan

Gave an update of his study of the scattering angle dependence of the cross-section. He used the radiated Bosted model and calculated the cross-sections with three different scattering angle. And the results shows ~20% difference. More details can be seen in his slides here.

• Jie

Gave an update on his study of the yield drift problem. He is still working together with Pengjia to correct the beam current dependence of the beam position. He summarized the beam current distribution for all production runs and found that ~90% of our data was taken with current less than 50 nA, where the beam position need to be corrected. He also studied the "sudden jump" of the beam position which means that the BPMA and BPMB readout did not changed much but the reported beam position changed a lot. It probably could be explained by the pedestal change but still need more study. More details can be seen in his slides here.

## 4/20/2016

Present: JP, Karl, Alex, Chao, Ryan, Toby, Jie, Vince, Ellie

Feature Presentations:

• Ryan

Gave an final update of the nitrogen cross-section study of the saGDH experiment. The radiative correction is done and the uncertainty carry-over from the elastic tail analysis is 1.5%. The radiative correction is calculated in two different way: the classic unfolding and the ratio of un-radiated and radiated Bosted model. He also did a bin center correction and compared the result with Vince's calculation. Two methods agrees at a 1-2% level. The radiative corrected cross-section for each kinematics setting is summarized in his slides and he will prepare a tech note for the analysis. More details can be seen in his slides here.

## 4/13/2016

Present: Karl, Chao, Ryan, Toby, Jie, Vince, Ellie

Feature Presentations:

• Jie

Gave an update on his study of the yield drift problem. Last time he showed some plots which indicates that the beam position might not be accurate and he did some study on this problem. He found out that the BPM readout shows some linear relations with the beam current. After carefully check the data, it seems that only the BPM B have this correlation. And this problem could be found in all beam energy settings. The uncertainty of beam position is very large if this problem is not corrected. More details can be seen in his slides here.

• Ryan

Gave an correction to his presentation on last week. He mentioned there was a mistake when he compared the formulation for the full internal bremsstrahlung tail and the angle-peaking approximation. And the results agree after the mistake was corrected. More details can be seen in his slides here.

## 4/6/2016

Present: JP, Karl, Chao, Ryan, Toby, Jie, Vince, Ellie

Feature Presentations:

• Ryan

Gave an update on his radiative correction study. He already studied the uncertainty for the elastic tail and he continued his study with the inelastic radiative correction. He explained how the angle approximation was applied in the internal bremsstrahlung. There is an equivalent correction in the angel approximation which is dropping the soft photons compare with doing a full integration. Difference between these two calculation is 5-10% for proton. He is still working on applying the calculation to other nuclei like Nitrogen. More details can be seen in his slides here.

• Toby

Gave an update on the his calculation of the asymmetry and cross-section. He applied the dilution factor calculated from the data to the asymmetry calculation. On the other side, he also applied the radiative correction factor calculated from the MAID model to the asymmetry calculation. He then applied the same factors to the cross-section calculation and got the cross-section and cross-section differences. The dilution seems not continuous and JP suggests to do a deeper study for each momentum in the longitudinal setting to understand what is the reason, for example the yield problem studied by Jie. More details can be seen in his slides here.

## 3/23/2016

Present: JP, Karl, Chao, Ryan, Toby, Jie, Vince, Ellie

Feature Presentations:

• Jie

Gave an update on his study of the yield drift problem. He continued his study with dilution runs. The method he used is similar as what he did for the production runs. He made a 6mm radius circle cut and compare the simulation result with the data. There are a few runs which were measured with beam current less than 50nA. After discussion with Pengjia, Jie mentioned that those runs' BPM readout might not be accurate since the BPM is calibrated at 50nA~100nA. He will do further study together with Pengjia to understand this effect. More details can be seen in his slides here.

## 3/9/2016

Present: JP, Karl, Chao, Ryan, Toby, Jie, Vince, Ellie

Feature Presentations:

• Toby

Gave an update on the dilution study. He summarized the dilution calculation for the 2.2GeV 5T transverse settings. He also used the dilution result to calculate the asymmetry for this setting. The radiative correction was considered in the calculation. And he concluded that the uncertainty of the calculation is dominated by the packing fraction uncertainty. More details can be seen in his slides here.

• Ryan

Gave an update on his cross-section analysis of the small angle GDH data. Based on the discussion from previous meetings, he checked the uncertainty of the elastic tail. The calculation includes three different sources: the correction factor representing higher order virtual photon diagrams, bremsstrahlung and multiple photon corrections. For the multiple photon corrections, he mentioned that G.Miller has an alternative multiple photon correction result. He applied the calculation to the saGDH data and it seems that the Miller multiple photon result is better representation of saGDH elastic tails. More details can be seen in his slides here.

• Jie

Gave an update on his study of the yield drift problem. He and Pengjia fixed the problem in the raster size calculation. He then made some cuts on the raster size to remove the boundary effect. He mentioned some of the runs had hot spot and was able to be corrected by the raster cut. He also summarized the yield spread with raster cuts for all kinematic settings. More details can be seen in his slides here.

## 2/24/2016

Present: Karl, Chao, Ryan, Toby, Min, Ellie, Jie

Feature Presentations:

• Toby

Gave an update on the dilution study. He need the scattering angle to calculate the scaling factor between the carbon and nitrogen. However, his study suggests that the scattering angle calculated for the carbon target is larger than the production target. The simulation shows opposite result which is expected to be reasonable from geometries. People suggests Chao to check the scattering angle calculation in the optics package. More details can be seen in his slides here.

## 2/17/2016

Present: JP, Jixie, Chao, Ryan, Min, Ellie, Jie

Feature Presentations:

• Chao

Gave an update on the optics study. He finished the matrix recalibration on right arm. The database is updated and is ready to use. The RMS values for angle and momentum calibration are summarized in his presentation. JP and Jixie has some concern about the broken septa seems to cause worse effect on left arm comparing with right arm. They suggested to check this more carefully. More details can be seen in his slides here.

• Ryan

Gave an update on his cross-section analysis of the small angle GDH data. Based on the discussion from the last week's meeting, he removed the extrapolation part in RADCON and then test the code with some test cross-sections from Pbosted Model. There is no problem in this case. So he compared the Pbosted model with saGDH data at large $\nu$. He is waiting for the response from Vince about the uncertainty of the saGDH cross-section at large $\nu$. More details can be seen in his slides here.

## 2/10/2016

Present: JP, Karl, Alex, Jixie, Toby, Chao, Ryan, Min, Ellie, Vince

Feature Presentations:

• Ryan

Gave an update on his cross-section analysis of the small angle GDH data. He is dealing the problem that after doing the tail subtraction and radiative correction the cross sections go negative at high $\nu$. He did a refit of the few low $Q^2$ points using a charge form factor fit. The results still deviated from the PBosted model at high $\nu$. However, JP and Karl suggests that the code RADCOR code should not give negative cross section result. There might be some problems in the extrapolation part. Karl suggests to check the input data to see if there are constrains at the high $\nu$ region. More details can be seen in his slides here.

## 2/3/2016

Present: JP, Karl, Alex, Jixie, Toby, Jie, Chao, Ryan, Ellie, Vince

Feature Presentations:

• Min

Gave an update on her acceptance study. She continued to compare the simulation result with data. Since the optics database is updated with the vertical beam position correction. The result suggests that the delta distribution is improved however the phi distribution still shows large discrepancy. She used this result to calculate the acceptance factor and applied it to the cross-section calculation. The result shows a factor of two difference. JP suggests that the acceptance calculated from the compare between the simulation and the data could still be influenced by the cross-section difference at small scattering angle. More details can be seen in her slides here.

• Toby

His presentation on 1/12 is reviewed. JP mentioned his concern about the uncertainty propagation. Toby is going to check it again and update his tech note about it.

General Discussion:

• The replay package is restored on the work disk.
• Toby will talk to Melissa and take over her packing fraction study.

## 1/26/2016

Present: Jixie, JP
By Phone: Jie, Chao, Ryan, Ellie

General Discussion:

• The analysis meeting will be moved back to 10 am Wednesday starting from next week.
• There is no meeting room available thus everyone will join by bluejeans. The meeting ID is 4828802914.

## 1/12/2016

Present: Melissa, Jixie
By Phone: Jie, Chao, Ryan, Toby, Ellie

Feature Presentations:

• Ryan

Gave an update on his cross-section analysis of the small angle GDH data. yield study using simulation. He is working on the problem that after doing the tail subtraction and running the inelastic Radiative Correction code the fully corrected cross sections go negative at high $\nu$. To solve this, he did a fit on the Nitrogen form factor. During the fitting, two models is considered: the oscillator model and the Fermi Model and the Fermi Model is proved to be better. He will complete the calculation of the elastic tail by using the form factor in a few weeks. More details can be seen in his slides here.

• Toby

Gave an review on the polarization uncertainty estimation. He claimed that the reason of the small uncertainties for the target polarization is because we took large amount of TE for each material. Thus the uncertainty of the calibration constant is reduced by average. Jixie suggests that the error propagation still need to be carefully checked. More details can be seen in his slides here

General Discussion:

• Chao updated his optics technical note.
• There is no meeting next week due to the Hall A collaboration meeting.