G2p Analysis Minutes

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Minutes of the weekly analysis meetings


Agenda



07/12/2017

Present: Ryan, Toby, Karl, Ellie, David

Feature Presentations :

  • Ryan

07/05/2017

Present: Ryan, Karl, Toby, J.P., Chao, David

General Discussion:

  • Batch farm is prioritizing multi-threaded jobs so this will impact g2p replay and also Chao's acceptance simulation timeline.
  • Toby is going to start looking at the 2.5T dilutions this week.
  • David has generated asymmetries but results are consistent with zero so he will try larger binning (up from 10 MeV)

06/28/2017

Present: Ryan, Toby, David, Karl, Chao, JP, Alexandre, Xiaochao, Ellie

General Discussion:

  • 2.5T data quality. Based upon error bars from a quick moment analysis of the 2.5T data from Ryan it appears that the 2.2/1.7 GeV data is useful for publication with Q2 values of approx 0.04 GeV2 and 0.02 GeV2, respectively. The 1.1 GeV data error bars are very large, which is in part due to the very small asymmetry prediction at that low Q2 (0.009 GeV2).
  • Toby is leaving to start a job on July 24. He will try and get something together for the dilution and packing fraction analysis for the 2.5T settings.
  • Chao is making good progress with the longitudinal acceptance for the carbon data. He is able to produce a continuous spectrum with good agreement in the overlap regions at large nu. Unfortunately there is no overlap around the delta-resonance. He will do a similar study except at the transverse settings next.
  • David is going to work on the data quality check for the 2.5T asymmetries. His first step is to produce g2p asymmetries and compare to results from Ryan and Toby.

06/21/2017

No meeting because of Hall A collaboration meeting.

06/14/2017

Present: Ryan, Karl, Toby, J.P.,Chao

Feature Presentation :

  • Ryan

Showed the results of a quick analysis of the 1.7 and 1.1 GeV 2.5 T settings. The 1.7 GeV data looks pretty good and can most likely be used going forward. There is one momentum setting just previous to the delta where the majority of the data was taken with a mismatched septa and dipole configuration, so it is not included in these slides. He will try including this data to see the effect it has on the results. It should probably be OK for the asymmetry. The 1.1 GeV data looks worse statistically, which related to the much smaller asymmetry that we see as we go to lower and lower Q2. As we go to lower Q2 we also have the added complication of the Christy fit we're using for the unpol XS getting worse and worse. Going forward Ryan will do a quick moment analysis of this data. More details on his slides can be found here.

  • Toby

Showed different methods for calculating the low-x portion of the BC sum rule. These include the polarized PDF's and Hall B model. The problem is that none of these methods are really applicable at the g2p kinematics (PDF's hold down to Q2 = 1 GeV2), and that the low-x portion of the integral must be a sizable contribution for the BC sum rule to hold. Going forward we will most likely assume that the BC sum rule holds and use that assumption to place a limit on the low-x behavior of g2 at low Q2. More details on his slides can be found here.

06/07/2017

Present: Ryan, Karl, Toby, J.P.,Chao, Ellie

Feature Presentation :

  • Ryan

Showed the results of a quick analysis of the 2.2 GeV 2.5 T settings. The goal of this analysis was to check the overall quality of the data and includes the combined statistics of both the RHRS and LHRS. The overall statistical precision of the data is pretty good considering the much lower target polarization of the 2.5T settings (15% on average compared to the 70% for the 5T runs). Going forward he will do a similar study for the 1.1 GeV and 1.7 GeV settings and also complete a very preliminary moment analysis of these settings. These settings also need a completed dilution and packing fraction analysis slides.

Verbal Updates:

  • Jie

Published his BPM tech-note update to the wiki.

  • Chao

Summarized his acceptance study progress. So far he has applied his 8mm raster cut method (+/- 15mrad in ph and 20 mrad in th) to the elastic carbon long. setting and gets 5% agreement between the simulation and data. He is able to drastically reduce the uncertainty in the raster cut by cutting on current and not size. The timing information of the raster is known very well. He knowns the time the raster spends inside the area of the cut and the time it spends outside. The ratio between these two times is scaled to the total charge. He is currently applying this to all the carbon dilution data at longitudinal to see how this procedure works at other P0. He estimates this will take 2-3 weeks. After that he will move onto the transverse setting and estimates that will take an additional 1-2 months to complete.

05/31/2017

Present: Ryan, Karl, Toby, J.P.,Chao

Feature Presentation :

  • Toby

Showed an update on his g2 moment calculations. His moments included the BC sum rule and also DeltaLT. From his analysis it was concluded that it is very difficult to verify the BC sum rule at low Q2 because of the lack of data at low x. The DeltaLT results look much better. More details on his slides are found here.

Verbal Updates:

  • Jie

Still working on his BPM tech-note/update.

  • Chao

Planning on talking with JP about his acceptance study update. Had to leave early to go to another meeting.

05/24/2017

Present: Ryan, David, Karl, Toby, J.P., Jie, Ellie

Feature Presentation :

None

Verbal Updates:

  • Jie

Still working on his BPM tech-note/update. Hopes to have it done by next week. This might also be his last g2p meeting before he starts his new job. Will also add his thesis to the wiki.

05/17/2017

Present: Ryan, David, Karl, Toby, J.P. Chao

Feature Presentation :

  • Ryan

Showed an analysis for an explanation for why the 2.2 GeV Longitudinal polarized DS does not go to zero below the pion production threshold after tail subtraction. His idea is that the elastic radiative events come from a different part of the acceptance than the inelastic events. This effect could be potentially large if a large acceptance cut is used. The big unknown in this analysis is what is the exact angle difference. With the current reconstruction/simulation status it's very difficult to determine. In the future, if the simulation is able to reproduce the angular acceptance then the tails can be calculated and weighted for the simulated acceptance. This also raises potential problems for getting a polarized DS from an asymmetry and cross section calculated with different acceptance cuts. For now, the analysis will proceed with the old method and assume one scattering angle. Ryan will check the results of using a tight asymmetry and tight cross section cut to see how the tail subtraction is effected. More details on his slides are found here.

  • Chao

Showed an update on the optics simulation and he is currently trying to beat down the systematic error from making a raster cut. He is currently cutting on raster current as opposed to raster size to improve the uncertainty. With a raster cut the simulation is much better able to reproduce the data.

05/10/2017

Present: Ryan, Jie, David, Toby, Ellie, JP

Feature Presentation :

  • Ryan

Showed an analysis update of the results section of his thesis and includes analysis of all of the 5T settings. He evaluated the g1 moments and the hyperfine splitting contributions for g1 and g2. More details on his slides are found here.

05/03/2017

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

Feature Presentation :

  • David

Showed an update for calculating the acceptance correction by normalizing to the elastic cross section. His uncertainty in this method is slightly better than the results Toby showed before and his dominant uncertainty is the scattering angle reconstruction and it's effect on the Mott XS and elastic form factors. He will look into further separating the quasi-elastic and elastic peaks by subtracting out the elastic tail for helium-4. More details on his slides are found here.

4/26/2017

Present: Ryan, Jie, David, Karl, Toby, Ellie

Feature Presentation :

  • Ryan

Showed results of a parallel asymmetry analysis between Toby and Ryan. The asymmetries agree very well and the only slight difference is at the longitudinal setting. This difference is a result of slightly different acceptance cuts used in the analysis and goes away if the same cuts are used. More details on his slides are found here.

  • Toby

Posted an update on last weeks slides to include a model comparison to his calculated cross sections. His slides are found here.

4/19/2017

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

Feature Presentations :

  • Toby

Showed a comparison between calculating polarized cross sections using a model and using data. In the data method he multiplies the raw asymmetry by the raw cross section with no dilution correction. In the model method he applies the dilution to the asymmetry and then uses a unpolarized proton model (radiated). The two results agree pretty well except for the 3.3 GeV setting where the yield drifts present problems with the dilution and cross section calculation. We will most likely have to use a model at this setting. More details on his slides are found here.

Verbal Updates:

  • Chao

Talked about using the raster cut in the simulation to match data and simulation for the acceptance. He's going to soon try and apply this raster cut method across the momentum settings at the longitudinal setting and see how well the simulation can match data. He's currently using a 30 mRad phi cut, which is significantly larger than the cut Toby is using and will the systematic uncertainty from knowing the cut boundary. There is going to be an additional systematic from using a raster cut when it comes to calculating the accumulated charge. He is looking into this.

4/12/2017

Present: Ryan, Jie, David, Karl, Toby, JP, Ellie

No presentations this week. Toby and Ryan are working on comparing their asymmetry results to confirm that their methods agree. Jie's graduation date is May 9 and he is still working on finishing up his thesis.

3/29/2017

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

Feature Presentations :

  • Ryan

Showed an update including the Gamma1 and GDH moment calculations. The results have very good statistical error bars when compared with the Hall B data and also his integration of the Hall B data agrees with the published Hall B results. More details can be found in his slides here.

  • Chao

Showed an update on the simulation for Run 5612. He is able to reproduce the edges of the acceptance better if he places a very tight cut on the raster size. This suggests a beam position reconstruction issue. Going forward he is going to look at the uncertainty introduced by this raster cut and see which has the larger contribution to the uncertainty: raster cut or acceptance cut. More details can be found in his slides here.

3/22/2017

Present: Ryan, Jie, David, Karl, Toby, JP, Chao

Feature Presentations :

  • Ryan

Showed a comparison between the Bosted model and low Q2 SLAC data. The agreement between data and the model is better at larger Q2 and around 15% at the 5T setting kinematics. Ryan is waiting on an updated model from Eric Christy that includes the low Q2 data in the fit. More details can be found in his slides here.

  • Toby

Also showed a comparison between the Bosted model and the SLAC data but included a preliminary g2p cross section as well. The agreement is at the 15% level with our data. More details can be found in his slides here.

  • David

Showed a method for calculating the helium-4 elastic cross section from g2p empty dilution runs. He compares the g2p data to the Rosenbluth result from the MSW (McCarthy-Sick-Whitney) form factors and get's agreement at the 10% level. He will look into adding systematic uncertainty estimates to both his measured and calculated quantities. He will also investigate the 'Delta E' term in the elastic peak radiative corrections. More details on his slides can be found here.

Verbal Updates:

A request was made by Eva-Maria Kabuss for some g2p slides to present at DIS 2017 (April 3-7).

3/15/2017

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

Feature Presentations :

  • Chao

Showed an update on the optics and acceptance simulation. He showed that for a carbon run with no liquid helium and at the longitudinal target configuration he is able to match data to simulation with a very tight acceptance cut. He is working on expanding this cut to reduce the overall systematic uncertainty in the acceptance. Super elastic events and carbon excited states make expanding this range difficult. More details on his slides can be found here.

Verbal Updates:

  • Jie

Graduation date is set for May 9, 2017.

3/8/2017

Present: Ryan, Jie, David, Karl, Toby, JP

Feature Presentations :

  • Ryan

Showed an update on how he is extracting g1 from the longitudinal data and evolving it to a constant Q2. He also showed a preliminary calculation of the gamma0 moment, which agrees well with the current Hall B measurements and chiral perturbation theory predictions. More details on his slides can be found here.

3/1/2017

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

Feature Presentations :

  • Ryan

Showed an update on the systematic error analysis going into the asymmetries, polarized cross sections and radiative corrections. Currently the dominating systematic error is from the angle reconstruction and use of an unpolarized model to create the polarized cross sections. The angle reconstruction error is amplified at low angles because of the strong Mott dependence. The unpolarized cross section systematic could be reduced in the future by substituting in g2p data for that component. More details on his slides can be found here.

  • Jie

Gave an update on the BPM calibration process. Showed that there is a strong position dependence to the off-sets determined from Harp scans. Through the reconstruction procedure he is unable to reproduce the location of the harp scan points because of this position dependence. More details on his slides can be found here.

  • Toby

Presented the status of the dilution analysis for the 3.3GeV settings. The analysis is complicated by the large yield drifts seen in the data. He is still trying to figure out a method to give reasonable dilution results at this setting. But whatever method he settles on will most likely come with an increased level of systematic error. More details on his slides can be found here.

2/22/2017

Present: Ryan, Toby, David, Jie, JP

Feature Presentations :

No feature presentations this week. Everyone is planning on presenting next week.

2/15/2017

Present: Ryan, Toby, David, Jie, JP

Feature Presentations :

  • Jie:

Showed an update the BPM calibration. There was some discussion on the base assumptions Jie is making in removing potential position dependence on some calibrations constants (b-/b+). More details on his slides can be found here.

General Discussion :

  • Toby:

Updated target polarizations are available now.

  • Ryan:

HERMES publication from 2013 of new BC Sum Rule calculation at Q2 = 5 GeV2. Data is consistent with 0 but with large error bars.

2/8/2017

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

Feature Presentations :

  • Ryan:

Showed the final systematics for the inelastic and elastic RC's. The end result is 2-3% for the elastic tail and 3-5% for the inelastic RCs. More details on his slides can be found here.

General Discussion :

  • Toby:

Updating his systematic uncertainty on the target polarization analysis.

2/1/2017

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

Feature Presentations :

  • Jie:

Gave an update on the BPM analysis. Still have trouble solving the position jumps. More details on his slides can be found here.

  • Ryan:

Showed the outline of the g2p radiative corrections procedure, including the polarized elastic tail and RADCOR and POLRAD formulations of the inelastic RCs. Also presented systematics for the unfolding procedure. He will next finalize the theory systematics for the RCs. More details on his slides can be found here.

  • Chao:

Gave an update on the acceptance study. He showed that at the longitudinal setting the shift from 0 in the theta_tg histogram is caused by the target field. The effect is more pronounced at transverse settings. More details on his slides can be found here.

General Discussion :

  • Toby:

g2p dilutions are now available on the wiki.

1/18/2017

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

Feature Presentations :

  • Jie:

Hoping for a May graduation with his thesis split between three topics (g2p is one). Point was made that Jie must finish his BPM study before graduation because at this point he is the only one that can do it. More details on his slides can be found here.

  • Toby:

Hoping for a May graduation with a close-to-final g2 his goal for his thesis. Finishing up the dilution analysis for 3.3 GeV 5T. More details on his slides can be found here.

  • Ryan:

Hoping for a June-August graduation with a close-to-final g2/hyperfine point his goal for his thesis. Finishing up the g2p radiative corrections procedure setup. More details on his slides can be found here.

  • Chao:

Gave an update on the acceptance study. He is still having a hard time matching the simulation to data. More details on his slides can be found here.

General Discussion :

  • Karl:

is looking into the EG1b data for our highest Q2 settings as the parallel component for g2.

1/11/2017

Present: Ryan, Toby, Karl, Jie, David, Chao

Feature Presentations :

  • Ryan:

Showed the effect a 0.3 degree scattering angle difference between HRSs would have on the data. Calculated this difference using models and then compared the data to it. The data is consistent with a straight line fit at 0, so the statistics of g2p are not sufficient to make a definitive statement. Also showed a calculation for the uncertainty in the out-of-plane polarization angle using a psuedo Monte-Carlo method. The uncertainty is around 1%. Details of his slides can be found here.

1/04/2017

Present: Ryan, Toby, Karl JP, Jie,

Feature Presentations :

  • Ryan:

Showed an update on the comparison between the LHRS and RHRS asymmetries for 2.2GeV 5T transverse. Using course 70 MeV bins and cutting out runs with large livetime and charge asymmetry he was able to get good agreement between the two spectrometers. The agreement is independent of the out-of-plane polarization angle correction. There is some question about the effect of the minor difference in the scattering angle between HRS's and the asymmetry. He will present on this difference at the next meeting. More details on his slides can be found here.

  • Jie:

Still looking into the BPM calibrations and the source of the BPM position jumps that don't see a corresponding yield change. He hopes to have this analysis wrapped up by the end of January. More details on his slides can be found here.

  • Other news:

At the 1/18/2017 weekly meeting we're planning on having a discussion on the analysis path forward. The primary focus on this discussion will be the experimental cross sections.

12/21/2016

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

Feature Presentations :

  • Toby:

Showed an update on the packing fraction analysis with a new method that is similar to his dilution calculation. This method gives a lower uncertainty than his elastic fit method. His two methods agree within the uncertainties for almost all of the settings. He will check the few kinematic settings where this isn't true and also try to pin down the systematic error from using the Bosted model to scale C12 to N14. More details on his slides can be found here.

  • Other news:

Vince's last day at g2p meetings. Good luck at your new job Vince!

12/14/2016

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

Feature Presentations:

  • Jie:

Showed a status update on the BPM calibration procedure. More details can be found in his slides here.

  • Chao:

Still having trouble matching the width of the simulation peaks to peaks from data. Even getting rid of all apertures did not sufficiently widen the simulation peak. He is continuing to look into it. More details can be found here.

12/07/2016

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

Verbal Updates:

  • Toby

Working on getting his dilution code back up and running

  • Ryan

Working on asymmetry comparisons between the LHRS/RHRS at 2.2 GeV 5T Transverse.

  • Jie

Talking with Pengjia still about the BPM calculation procedure. Will give an in-depth update on the status of the BPM analysis at the next meeting.

11/30/2016

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

Feature Presentations

  • Ryan

Showed an update on the out-of-plane polarization angle calculation. The calculation agrees with Chao's result but still seems too large (40 - 65 degrees). Chao is working on confirming the results. Details of his slides can be found here.

  • Toby

Showed an update on the packing fraction analysis. He presented final values for all settings except for 1.1 GeV 2.5 T. The difficulty at this setting is that the quasi-elastic peak is barely separable from the elastic peak so he is unsure of how to fit it. This is also a problem at the other 2.5 T settings and is manifest in the larger systematic uncertainties. Details of his slides can be found here.

Verbal Updates:

  • Chao

working on out-of-plane polarization angle calculation and will also confirm the proton elastic simulation results for Toby.

  • Jie

Talking with Pengjia still about the BPM calculation procedure.

11/23/2016

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

  • Jie

Discussed BPM calibration method

  • Ryan

Working on calculating the out-of-plane polarization angle, with help from Chao. Hoping to confirm method with Chao and present something soon.

11/16/2016

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

Feature Presentations

  • Jie

Showed an update on the BPM calibration procedure. His correlation method for calculating the pedestals improves the uncertainty but does not affect the position reconstruction. In the calibration procedure there is an offset term that as large variations between calibration points. Pengjia fit this constant for current dependence but it is also possible it might have some positional dependence. Jie is going to talk with Pengjia about this. More details on his slides can be found here.

Verbal Updates:

  • Toby is working on finalizing the uncertainties for the packing fraction analysis and is running into some issues with g2psim.
  • Ryan is working on calculating the out-of-plane polarization angle, with help from Chao.

11/02/2016

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

Feature Presentations

  • Ryan

Showed a brief update on calculating the out-of-plane angle correction to the perpendicular polarized cross sections. He will talk to Chao about how to make this calculation using the reconstructed variables in the replayed ROOT files. More details on his slides can be found here.

  • Toby

Showed a slide on the yield spectra for the elastic runs in PF analysis at all kinematic settings. The nitrogen and helium peaks are only clearly visible at the 2.2 GeV 5T transverse setting, so he will need to adjust his fitting routine to account for this at the other settings. More details on his slides can be found here.

10/26/2016

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

Feature Presentations

  • Ryan

Showed an update on the polarized radiative corrections using POLRAD at the g2p kinematics (non-constant scattering angle). He showed that using the same angle fit for all the input spectra (as opposed to individual fits representing measured data) the systematic error was similar to that of data taken at a constant scattering angle. For this study he used the MAID 2007 model. He recommends using models for the RC'ing of g2p data but those models could be tuned and checked using measured data. More details on his slides can be found here.

Verbal Updates:

  • Chao

Working on the optics and acceptance simulation and tuning the simulation aperatures. Showed a short slide with better agreement between data and simulation. Still working on improving this.

  • Jie

Working on the BPM position calibration procedure.

10/19/2016

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

Feature Presentations

  • Toby

Showed an update on his method for calculating the packing fraction, along with his estimate for the systematic uncertainty. He's hoping to finalize the results for the 5.0 T settings within the next few weeks. More details on his slides can be found here. There was some discussion that his uncertainty of ~8% in the fitting method is overestimated as described in the slides, so hopefully the systematic uncertainty is at the 10% level, maximum.

Verbal Updates:

  • Chao

Working on the optics and acceptance simulation and tuning the simulation aperatures.

  • Jie

Working on the BPM position calibration procedure. Still trying to fully understand Pengjia's method.

  • Ryan

Working on setting up inelastic radiative corrections procedure for changing angle of g2p.

10/12/2016

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

Feature Presentations

  • Jie

Showed final results for the BPM pedestal uncertainty using his new correlation method for the 2.2 GeV 5T transverse setting. The uncertainties are about a factor of 3-4 better than previous and are approx. 1mm and 1mrad at the target. He is moving on to finishing this study at other settings and also looking into the BPM calibration procedure and beam position jumps. More details on his slides can be found here.

Verbal Updates:

  • Chao

Working on the optics and acceptance simulation. Believes that the previous mismatch he showed with data and simulation at bigger angular acceptance was due to the simulation aperatures blocking more events than seen in the data. Current size estimates of the aperatures is from a combination of g2p survey and historical Hall A information.

  • Toby

Working on packing fraction results and updating the systematic error analysis. Hoping to finalize shortly.

  • Ryan

Working on setting up inelastic radiative corrections procedure for changing angle of g2p.

10/05/2016

Present: Ryan, Toby, Karl, Ellie, Jie, JP, Jixie

Feature Presentations

  • Ryan

Showed the reconstructed angle for a loose cut on all of the LHRS g2p production data. The fit is a combination of a linear and exponential fit; this form is suggested from a Jixie ELOG post. For the most part there is good agreement with the data to the fit, and outliers from the fit is a potential criteria for selection of good runs. He used these fits to mimic g2p data and test RC procedures on data at different angles. He found that he could do RC's with small systematic error if he used the same fit for all input spectra. This is not the case for g2p data, so he's working on improving the method. More details on his slides can be found here.

Verbal Updates:

  • Jie

Working on the BPM pedestal issue. He's now considering correlations between all channels in the BPM pedestals. This slightly increases his uncertainty but it is still smaller than Pengjia's result and helps alleviate the triple peak issue.

  • Toby

Working on packing fraction results and updating the simulation calculations needed for the cross section ratio input.

  • SPIN 2016

Chi-PT calculations of the polarizabilities are still bad. NEED DATA!

9/21/2016

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

Feature Presentations

  • Jie

Showed an update on the BPM pedestal calculation. Found a correlation between the pedestals on BPM channels. By using a rotated coordinate system, he can decouple the correlation. This allows for a reduced uncertainty in the BPM pedestal uncertainty contribution to the BPM calculation. More details on his slides can be found here. Will work on finalizing the updating uncertainty calculations and continue with checking the BPM calibration.

  • Ryan

Showed the reconstructed angles for three different asymmetry cuts for both the transverse longitudinal asymmetries. There is a difference between the hot-spot angle in the transverse asymmetry. The RHRS accepts smaller angles in the transverse configuration but this cannot account for the difference in the HRS asymmetries between L/R. More details on his slides can be found here. He will try different cuts on different variables to try and find a set that gives agreement between the LHRS/RHRS.

    • NO MEETING NEXT WEEK BECAUSE OF SPIN 2016

9/14/2016

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

Feature Presentations

  • David

Showed a statistical analysis between the LHRS and RHRS asymmetries for the 2.2GeV 5T transverse/longitudinal data. Concluded that for long. data the two spectrometers are statistically measuring the same thing. Further work still needs to be done on for the transverse asymmetries. His slides can be found here.

  • Toby

Showed an updated packing fraction calculation where he replaces fits to the quasi-elastic and quasi-elastic contamination with the Bosted model. His packing fractions are in much better agreement with this method and the consensus is that the fit method was driving the large differences previously seen. He was given suggestions on trying to better quantify the quasi-elastic contamination, including using other models and separating the kinematic regions using acceptance cuts. More details can be found in his slides here.

  • Jie

While on the schedule, he will present next week.

9/7/2016

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

Feature Presentations

  • Chao

Gave an update on the acceptance study of the 5T longitudinal setting. He's currently working on tuning the resolution of the simulation package. He finds that he can match the width of the elastic peak for a small range in theta and phi target but as he increases that range his simulation produces too narrow of a spectra. He is working on fixing this issue. His slides can be found here.

  • Ryan

Showed a comparison between the 5T longitudinal asymmetries using different acceptance cuts. He demonstrated that within our statistical error bars we do not need to make a bin-centering correction to the asymmetries for the longitudinal setting. He also tried to see if a model accurately described the asymmetry change with angle but was not successful. More details can be found in his slides here.

8/31/2016

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

Feature Presentations

  • Jie

Gave an update on the BPM pedestal analysis. He showed results from the pedestal analysis of beam trip runs for both the Happex DAQ and HRS DAQ. HRS DAQ has cleaner pedestals but the HRS DAQ is less precise. The pedestal shift seen in the HAPPEX DAQ is continuos with time. He will continue to look at the BPM calibration procedure and try and quantify the effect the pedestals have on the BPM uncertainty. More details can be found in his slides here.

Verbal Updates:

  • Ryan

Continuing to look at HRS asymmetry angle dependence

8/24/2016

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

Feature Presentations

  • Toby

Showed an update on the packing fraction analysis. He has been able to successfully fit the two elastic peaks (N2 and He4) and quasi-elastic peak to produce packing fraction results. He also presented an alternative calculation to the packing fraction, just using the helium peak from production and a dummy/empty run. His two methods agree at the ~10% level but differ greatly from what Melissa showed previously. Toby will continue to look at his fits and see if there is room for improvement there because there is some fit dependence on the result. One suggestion was to fit the simpler dummy run He4 elastic peak and use those fit parameters in the production runs. More details can be found in his slides here.

Verbal Updates:

  • Ryan

Continuing to look at HRS asymmetry angle dependence

  • Jie

Working on understanding Pengjia's BPM code.

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. Slides can be found here.

Verbal Updates:

  • 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.

Verbal Updates:

  • 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

Verbal Updates:

  • 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

Verbal Updates:

  • 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

Verbal Updates:

  • 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.

Verbal Updates:

  • 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.

Verbal Updates:

  • 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 <math>\nu</math>. He is waiting for the response from Vince about the uncertainty of the saGDH cross-section at large <math>\nu</math>. 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 <math>\nu</math>. He did a refit of the few low <math>Q^2</math> points using a charge form factor fit. The results still deviated from the PBosted model at high <math>\nu</math>. 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 <math>\nu</math> 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 <math>\nu</math>. 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.



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