|
|
| Line 100: |
Line 100: |
| | *Progress of acceptance study looks good, but could become an analysis bottleneck. | | *Progress of acceptance study looks good, but could become an analysis bottleneck. |
| | | | |
| − | ==12/17/2014==
| |
| | | | |
| − | Present: Min, JP, Jie, Jixie, Pengjia, Chao, Melissa<br>
| |
| − | By Phone: Vince, Toby, Ryan, Ellie<br>
| |
| − |
| |
| − |
| |
| − | '''Feature Presentations:'''
| |
| − | *Melissa
| |
| − | **Gave an update on packing fraction analysis. Previously, in her fitting routine to determine the level of "contamination" in the <br>elastic peak from the 2nd peak, she used a single Gaussian to fit the 2nd peak. For this time, she showed the updated fit to the <br>2nd peak, which includes the contributions from the Nitrogen quasi-elastic peak, the helium quasi-elastic peak, and the hydrogen <br>elastic peak. To understand the relative contributions from the different materials, she used the QFS model to help constrain the fit. <br>JP commented that the fermi momentum used for nitrogen (set to 240 MeV) may be slightly too large. Since the nitrogen parameters<br>(specifically the nucleon separation energy) are not as well constrained as the helium, she looked at the effect of adjusting these<br>parameters on the overal packing fraction. The effect is not large; this variation was included as part of the uncertainty. Next she will <br>work on extracting the packing fraction for different materials/settings, but first she will focus more on understanding the discrepancy <br>in the yields. More details can be seen in her slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/melissac/Elastic/Elastic_12_17.pdf here].
| |
| − |
| |
| − | *Min
| |
| − | **Gave an update on her acceptance study. To do the forward transport, she uses a forward transport function to go from the target <br>plane to the virtual plane, then applies a correction, then uses a forward transport function to go from the virtual plane to the focal plane. <br>A single function is used to do the transport backward from the focal plane to the target plane. This has been incorporated into the <br>g2psim package; the value for δ used in g2psim must be consistent with the value for δ used in the fits. At the focal plane, <br>she used the focal plane, dp and beam cuts from the data in the simulation. For the reverse transport to the target plane, she used the <br>exact same trajectories from the data to calculate x, y, θ, φ and δ and do the fit. Previously, she had tried using SNAKE to <br>generate a bunch of trajectories in the range of the acceptance to use for the fits, but found a discrepancy between the data and simulation <br>results. Next she will update the fits and compare the value of δ using the updated g2psim energy loss model. She will also look at <br>other dp settings and do a comparison of target y. More details can be seen in her slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/mhuang/12172014/12172014.pdf here].
| |
| − |
| |
| − |
| |
| − | '''General Discussion:'''
| |
| − | *As discussed at the last collaboration meeting, we will have an "unofficial" collaboration meeting on January 7th, during the normal meeting <br>time, in order to re-evaluate what progress has been made. All students should plan to give a short update (~5 minutes) on the status of their <br>analysis projects and a plan for the future.
| |
| − |
| |
| − | ==12/10/2014==
| |
| − |
| |
| − | Present: Chao, Pengjia, Yunxiu Ye, Jie, Min, JP, Jixie<br>
| |
| − | By Phone: Toby, Ryan, Ellie, Vince<br>
| |
| − |
| |
| − |
| |
| − | '''Feature Presentations:'''
| |
| − | *Toby
| |
| − | **Gave an update of the yield check for the 3.3 GeV energy setting. For 2.490 GeV momentum setting, the beam position looks stable <br>and different cuts on raster pattern does not suppress the yield spread. Pengjia suggests that the bpm available cut should be applied <br>to cut off the beam trips. He also checked the 2.2 GeV energy setting with 5.0 T transverse target field. In this case, the raster pattern <br>indicates some beam scraping in the runs with higher rate for 1.600 GeV setting. The other momentum settings looks reasonable. <br>Currently he is checking the 2.2 GeV, 5.0T longitudinal setting and may give a report next time. More details can be seen in his slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/toby/g2p%20meetings/12.10.14.pdf here].
| |
| − | *Jie
| |
| − | **Gave an update on trying to match the dp distribution between simulation and data. Compare to last time, he enlarged the smearing <br>of the focus plane variables by a factor of 10. The elastic peak of empty target (pure Helium) is still narrower than the data if there is no <br>cut on beam position. If the raster is cut with in a 2 mm radius circle, the width of the elastic peak agrees with the data but the central <br>value has a deviation. JP suggests him to use the most recent HRS transport functions from Min. More details can be found in his slides <br> [http://hallaweb.jlab.org/experiment/g2p/collaborators/jie/2014_12_10_simulation/Simulation_update_2014_12_10.pdf here].
| |
| − |
| |
| − |
| |
| − | '''General Discussion:'''
| |
| − | *Toby need help form other students to check the yields. He will send an email about remaining tasks.
| |
| − |
| |
| − | ==12/3/2014==
| |
| − |
| |
| − | Present: Chao, Pengjia, Yunxiu Ye, Jie, Min, JP, Melissa<br>
| |
| − | By Phone: Toby, Ryan, Ellie, Karl, Vince, Xiaochao<br>
| |
| − |
| |
| − |
| |
| − | '''Feature Presentations:'''
| |
| − | *Pengjia
| |
| − | **Looked at the change in the asymmetry for different acceptance cuts. He compared the asymmetry without any acceptance cuts, and with <br>cuts applied on dp and φ. He also tried combining the events into 3 W-bins, to improve the statistics in each bin. JP pointed out that, in <br>doing this, you lose information on the structure. He showed the asymmetry comparison for all of the energy settings, using LHRS data. For <br> the 2.5T settings, the uncertainty is larger due to the low polarization. Once the RHRS optics is ready, the right arm runs can also be included <br>to improve statistics.
| |
| − | **He also calculated the ungated total charge for each run and added it to the mysql database. He calculated the charge by taking the average <br>between the upstream and downstream sis3800, counting the charge between the first and last event. He checked the calculation using the <br>sis3801 and happex bcm values. More details can be seen in his slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/pzhu/12032014/asym_correct_accep.pdf here].
| |
| − |
| |
| − | *Min
| |
| − | **Gave an update on focal plane matching. A transport function is used to go from the target plane to the virtual plane, where a correction is <br>applied, and then a transport function is used to go from the virtual plane to the focal plane. This has been incorporated this into the g2psim <br>transport package. She showed a comparison between simulation and data of x vs y and θ vs φ. Overall the result looks good. In the θ vs<br> φ plot, there seems to be some strange structure in the last row of sieve holes. This only appears in the simulation results, so it's likely <br>due to the fitting function used in the simulation. She is also working on updating the fit of the reverse functions; the updated transport <br>functions alter the reverse functions. Once the energy loss model is updated in the g2psim package, she will update the fits. More details <br>can be seen in her slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/mhuang/12032014/12032014.pdf here].
| |
| − |
| |
| − | *Chao
| |
| − | **He has uploaded a draft of a technote on the helicity decoder [http://hallaweb.jlab.org/experiment/g2p/collaborators/chao/technotes/Chao_TechNote_HelicityDecoder.pdf here]. He would appreciate any feedback.
| |
| − | **Also gave an update on optics calibration for the RHRS. Previously, he showed that one of sieve holes had some strange structure in the dp <br>distribution. He compared the distribution from this sieve hole (7.6) to neighboring sieve holes, but the odd structure in the dp distribution <br>seems to be unique to this hole, suggesting that the beam was hitting some additional material. Since this issue was also seen in the LHRS <br>optics data, it's possible that there was something in the target chamber (symmetric on both sides) that is in the beam trajectory. More details <br>can be seen in his slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/chao/20141203/Chao_WeeklyMeeting_12032014.pdf here].
| |
| − |
| |
| − |
| |
| − | '''General Discussion:'''
| |
| − | *Pengjia will give the update for g2p at the Hall A collaboration meeting next week. There will be a dry run on Friday, at 2pm in room F226.
| |
| − |
| |
| − |
| |
| − | ==11/19/2014==
| |
| − |
| |
| − | Present: Chao, Pengjia, Jie, Min, JP, Kalyan, Melissa<br>
| |
| − | By Phone: Toby, Ryan, Ellie, Karl<br>
| |
| − |
| |
| − |
| |
| − | '''Feature Presentations:'''
| |
| − | *Toby
| |
| − | **Gave a summary of yield drifts for the 3.3 GeV energy setting, including a breakdown for different momentum settings. The two worst <br>settings are 2.490 GeV/c (~15% spread) and 2.342 GeV/c (~8% spread), both for material 19. He showed a thorough breakdown of the <br>quantities he checked for the 2.490 GeV/c momentum setting, including beam energy, septum current, scattering angle, beam current and <br>raster pattern. There does seem to be some drift in the beam energy, which is due to the fact that there was no energy lock during this time <br>(since only Hall A was running). Ryan commented that, in testing the effect of beam energy using the Bosted model, a change in the beam <br>energy of 10 MeV only changes the XS by ~0.5%. For next time, Toby will check the scalers and beam position as a possible reason for the <br>drift in yields. More details can be seen in his slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/toby/g2p%20meetings/19.11.14.pdf here].
| |
| − |
| |
| − | *Melissa
| |
| − | **Summarized the momentum settings that have a discrepancy in the yields for the 2.2 GeV, 2.5T energy setting. For many settings, the <br>change in yield seems correlated to a change in beam position, specifically the x-position. The change in beam position often occurs when <br>there is a gap in time when the runs were taken. She will work with Jie to see whether the shift in beam position/yields matches with the <br>expectation from simulation. We may need to include an acceptance correction based on the change in beam position. She also showed the <br>yields for packing fraction runs taken in this energy setting for material 7. Between the first run (3503) and the other 3 runs (3574, 3727, <br>3864), a Moller measurement was taken, and afterwards the rate in the 3rd arm suggested the beam was scraping something. The raster size <br>was changed from 2cm to 1.8cm to fix this problem. She will try comparing events at the edge of the raster to the center of the raster between <br>these 4 runs to see if it corrects the problem. More details can be seen in her slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/melissac/Yields/Yields_11_19.pdf here].
| |
| − |
| |
| − | *Pengjia
| |
| − | **Gave an update on looking at the effect of different acceptance cuts on the asymmetry. He looked at the 2.2 GeV, 5T longitudinal setting, <br>and combined runs from material 17 and 18 to improve statistics. He varied the cuts on the reconstructed variables in the target plane; dp <br>φ and θ. He also showed an example of the 3D acceptance cut relationship. The asymmetry seems to be sensitive to the cut on φ, but not <br>as sensitive to the cut on θ. More details can be seen in his slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/pzhu/11192014/asymmetry%20for%20different%20acceptance%20cut4.pdf here].
| |
| − |
| |
| − | *Jie
| |
| − | **Gave an update on trying to match the dp distribution between simulation and data. Last time he showed that the elastic peak for and empty<br>run (only helium) is much narrower than the data. He have a breakdown of the values used for smearing the elastic peak. The beam energy <br>resolution is probably alright when the energy lock is on, but might be larger for runs where the lock was not on. The VDC resolution is probably <br>actually worse than what he is currently using. He also included the HRS resolution, which hadn't been included previously. Including the HRS <br>resolution widens the peak, resulting in a better match with the data for an optics run on carbon without liquid helium (including all the sieve <br>holes). However, for the same run, but only the center sieve hole, the simulated peak is actually wider than the data. Also, the comparison for <br>the empty run still results in a simulation result that is much narrower than the data. He will continue to work on this problem, and will update<br> the g2psim package with the newest version of the energy loss model More details can be seen in his slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/jie/2014_11_19_simulation/Simulation_update_2014_11_19.pdf here].
| |
| − |
| |
| − |
| |
| − | '''General Discussion:'''
| |
| − | *There will be no meeting next week, we will meet again on December 3rd.
| |
| − |
| |
| − |
| |
| − | ==11/12/2014==
| |
| − |
| |
| − | Present: Chao, Kalyan, Jie, Pengjia, Min, JP, Jixie, Melissa<br>
| |
| − | By Phone: Vince, Toby, Ryan, Ellie, Karl, Moshe<br>
| |
| − |
| |
| − |
| |
| − | '''General Discussion:'''
| |
| − | *The main goal of this meeting was to identify each students approximate timeline for graduation, and any specific requirements for their <br>thesis from their university. A brief summary is listed below, more details can be seen in the slides listed in the agenda [https://hallaweb.jlab.org/wiki/index.php/G2p_Weekly_Analysis here]:
| |
| − | **Melissa: Spring 2015
| |
| − | **Ryan: Spring 2016-Fall 2016
| |
| − | **Chao: August 2015
| |
| − | **Toby: Spring 2016
| |
| − | **Jie: Summer 2016
| |
| − | **Min: May 2015
| |
| − | **Pengjia: May 2015
| |
| − |
| |
| − | *For Friday's meeting, each student should also have a detailed short and long term plan for completing analysis goals before their <br>anticipated graduation date. If known, plans for after graduation should also be included.
| |
| − |
| |
| − | *Future paper topics were also discussed, possibilities include:
| |
| − | **Asymmetries
| |
| − | **g2
| |
| − | **Moments of g2 (BC sum rule, polarizabilities)
| |
| − | **hyperfine splitting
| |
| − |
| |
| − |
| |
| − | ==11/05/2014==
| |
| − |
| |
| − | Present: Jixie, Jie, Min, Chao, Pengjia, JP, Melissa<br>
| |
| − | By Phone: Toby, Ryan, Ellie, Karl, Moshe<br>
| |
| − |
| |
| − |
| |
| − | '''Feature Presentations:'''
| |
| − |
| |
| − | *Melissa
| |
| − | **Working on updating the fitting routine used in her packing fraction analysis. Currently, she is estimating the quasi-elastic peak <br>as a single gaussian, but really it contains contributions from multiple sources (nitrogen quasi-elastic, helium quasi-elastic and hydrogen <br>elastic). To better understand the different contributions, she is using the QFS model to determine the relative contributions to the peak. <br>She started with an empty dilution run to determine the parameters for helium, then the results to model carbon dilution run. The carbon <br> parameters could then be used to estimate the nitrogen parameters in modeling a production (ammonia) run. For next time, she will try <br>subtracting the elastic tail from the data, to better match the model with data. More details can be seen in her slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/melissac/Elastic/Elastic_11_05.pdf here].
| |
| − |
| |
| − | *Chao
| |
| − | **Gave an update on the status of optics calibrations. He tested the optics portion of the g2psim package for the RHRS, including ray <br>tracing and HRS transport functions; it seems to be working well. A small problem was found in the RHRS calibration; for one sieve hole, <br>the dp spectrum has additional structure, as if events were hitting something. This structure was only seen in one hole, and it wasn't seen <br>in the straight through data. JP suggested examining nearby holes to look for a gradual change in the dp distribution. He also showed the <br>results of using an event by event simulation to calculate the effective theta and phi angles. There appears to be some "smearing" in the <br>distribution of BPM X vs Y; JP suggested cutting out these smeared events for determining the effective theta and phi angles. He will <br>working on calibrations for the remaining energy settings and septum settings. More details can be see in his slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/chao/20141105/Chao_WeeklyMeeting_11052014.pdf here].
| |
| − |
| |
| − | *Pengjia
| |
| − | **Looking at the effect of different acceptance cuts on the asymmetry. He is looking at asymmetries for the 2.2 GeV, 5T setting for material <br>17. He started by fixing dp, y and φ and varying the cut on θ. He then followed the same procedure, but varying the cut on dp, y and φ. <br>Karl suggested that, since the error bars are so large, it might be useful to use larger W bins to get getter statistics. Pengjia will try this for <br>next time. More details can be seen in his slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/pzhu/11052014/asymmetry%20for%20different%20acceptance%20cut2.ppt here].
| |
| − |
| |
| − | *Ryan
| |
| − | **Uploaded a draft of a technote on radiative corrections [https://userweb.jlab.org/~rbziel/Weekly_Meetings/Unpol_Rad_Draft.pdf here]. He would appreciate any comments or feedback.
| |
| − |
| |
| − |
| |
| − | '''General Discussion:'''
| |
| − | *We will have a collaboration next Friday (Nov. 14th), the registration link and program can be found [https://hallaweb.jlab.org/wiki/index.php/14th_Nov%2C_2014 here].
| |
| − | *Students will prepare a 15/20 minute summary of analysis progress and future plans.
| |
| − | *For next week's analysis meeting, each student should come prepared with expected dates/time constraints for graduation along with any<br> specific requirements from their university.
| |
| − |
| |
| − |
| |
| − | ==10/29/2014==
| |
| − |
| |
| − | Present: Jie, Chao, Pengjia, Min, Kalyan, Jixie, Melissa<br>
| |
| − | By Phone: Toby, Ryan<br>
| |
| − |
| |
| − |
| |
| − | '''Feature Presentations:'''
| |
| − |
| |
| − | *Min
| |
| − | **Gave an update on focal plane matching. The focal plane data and simulation results at the target are matched using a fit at the "virtual<br> plane". She showed a comparison of simulation and data for the virtual plane fit, and for the focal plane projection. Overall, the results <br>look good! For now she has done a visual matching, but for next time she will include a quantitative comparison of the results. She will <br>continue with this acceptance study for next time. More details can be seen in her slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/mhuang/10292014/10292014.pdf here].
| |
| − |
| |
| − | *Jie
| |
| − | **Gave an update on the energy loss model being used in the g2psim package. Last time, he showed a comparison of different ionization <br>models for the straight thru case with a carbon target (no liquid helium) and found agreement between simulation and data. This time, he <br>checked the ionization model with different materials and compared the results with data. He compared the fluctuation model with the <br>(new) Landau function for both a layer of NH3 and a layer of LHe, and found consistency between the models for both materials. However, <br>in the comparison with data, he found that the width of the elastic peak in the simulation is much narrower than in the data. For next time, <br>he will provide a detailed list of what is included in the simulation. More details can be seen in his slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/jie/2014_10_29_simulation/Simulation_update_2014_10_29.pdf here].
| |
| − |
| |
| − | *Toby
| |
| − | **Gave an update on dilution analysis. For the 3.3 GeV energy setting, he has updated his results to include bin averaging (to account for <br>overlapping acceptance), which is weighted by statistical uncertainty. He also averaged over all the production runs at each momentum <br>setting, and included the systematic uncertainty from the nitrogen model. He moved on the to 2.2 GeV, 5T transverse setting and looked at <br>the discrepancy in the yields for some kinematic settings. He found that using an estimated total charge, as opposed to the helicity gated <br>total charge which is currently listed in the mysql database, solved the disagreement in the yields. He will continue to look in this problem. <br>More details can be found in his slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/toby/g2p%20meetings/10.29.14.pdf here].
| |
| − |
| |
| − |
| |
| − | ==10/22/2014==
| |
| − |
| |
| − | Present: Chao, Pengjia, Min, Moshe<br>
| |
| − | By Phone: Toby, Ryan, Ellie<br>
| |
| − |
| |
| − |
| |
| − | '''Feature Presentations:'''
| |
| − |
| |
| − | *Pengjia
| |
| − | **Gave an update on studying the effect of different acceptance cuts on the physics asymmetry. Target plane variables (x, theta, y, phi)<br> calculated by most recent optics package are chosen to apply cuts instead of the focus plane variables. An overall dilution factor 0.15<br> is applied to all runs instead of Toby's calculation. The physics asymmetries of 2.254 GeV longitudinal setting has been calculated<br> with different acceptance cuts. The result can be found in the elog entry [https://hallaweb.jlab.org/dvcslog/g2p/184 https://hallaweb.jlab.org/dvcslog/g2p/184]. More details<br> can be seen in his slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/pzhu/10222014/asymmetry%20for%20different%20acceptance%20cut.ppt here].
| |
| − |
| |
| − | *Chao
| |
| − | **Gave an update on optics calibration of right arm. The same method to calibrate target y variable of LHRS is applied to RHRS. The<br> sieve holes for upstream aluminum window can not be distinguished very well in some dp scan runs so the y calibration result are a<br> bit worse than LHRS. The results after the second iteration looks pretty good. The longitudinal field setting of RHRS only has one<br> optics run. Compare to LHRS, RHRS is more influenced by the broken septum but it seems still to be correctable. The optics calibration<br> with target field requires some input from simulation package. He is currently testing the simulation with right arm and the aluminum<br> window target. More details can be seen in his slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/chao/20141022/Chao_WeeklyMeeting_10222014.pdf here].
| |
| − |
| |
| − | *Ryan
| |
| − | **Gave an update on the study of Small Angle GDH nitrogen cross sections. Last time he showed a compare between Bosted model and<br> data which does not agree well at the quasi-elastic peak possibly caused by the 2 MeV binning. He rerun the analysis with a 10 MeV<br> binning in nu. He also made a change of handling of punch-through in elastic tail to make it consistent. After tuning, the overall scale<br> factors are with in +/-5%. He is curretly working on dealing with the jumps in the data. More details can be seen in his slides [https://userweb.jlab.org/~rbziel/Weekly_Meetings/g2p_102214.pdf here].
| |
| − |
| |
| − |
| |
| − | ==10/15/2014==
| |
| − |
| |
| − | Present: Chao, Jie, Pengjia, Min, Melissa <br>
| |
| − | By Phone: Toby, Ryan, Ellie<br>
| |
| − |
| |
| − |
| |
| − | '''Feature Presentations:'''
| |
| − |
| |
| − | *Min
| |
| − | **Gave an update on focal plane matching. The goal is to match focal plane data to simulation at the virtual plane. Previously, she <br>was doing the fit at the virtual plane using (x,θ,y,φ), this time the fit was done using (δ,θ,y,φ). Since δ doesn't change due to the<br> magnetic field, only θ, y and φ need to be fit. She showed the comparison between data and simulation without the fit and with up <br>to a 3rd order fit; the results match very well after the fit is applied. Next she will work on projecting onto the focal plane to make <br>the simulation match the data. More details can be seen in her slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/mhuang/10152014/10152014.pdf here].
| |
| − |
| |
| − | *Jie
| |
| − | **Gave more details on his update to the energy loss model. Previously, he showed a comparison of data with simulation, including <br>only the energy loss due to ionization in the simulation, and found that the simulation result was wider than the data. The ionization <br>model used in SAMC is a Landau distribution with the most probable value at 0 and a FWHM at 4ε. He updated the model to have <br> a most probably value of -0.22278 and a FWHM of ε. He compared both landau distributions to a fluctuation model, and found that <br>the updated Landau model (with FWHM=ε) matched much better than the previous model (with FWHM=4ε). He also showed a<br> comparison of data from a carbon run without helium with simulation results including the complete energy loss model (ionization,<br> internal and external Bremsstrahlung), which match reasonably well. Next he will work on comparing data with simulation for other <br>target types. More details can be seen in his slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/jie/2014_10_08_simulation/Simulation_update_2014_10_08.pdf here].
| |
| − |
| |
| − |
| |
| − | ==10/8/2014==
| |
| − |
| |
| − | Present: JP, Chao, Jie, Pengjia, Min, Kalyan, Melissa <br>
| |
| − | By Phone: Ryan, Ellie, Karl, Vince<br>
| |
| − |
| |
| − |
| |
| − | '''Feature Presentations:'''
| |
| − |
| |
| − | *Melissa
| |
| − | **Gave an update on packing fraction analysis. In order to combine yields from dummy and production runs, it is necessary to scale <br>the radiation lengths to match. The yields are generated using two different radiation thicknesses; one using the length of helium in <br>the dummy run, and the length of helium in the production cell. The ratio of these results gives the factor used to scale the radiation <br>length of the dummy run to match the radiation length of the production run. The scaling factor from using this method is close to 1. <br>Instead of using just the radiation length of helium in the production, the contributions from all materials should be considered, which <br>should make the correction larger. She is also planning to update her fitting routine to determine the contamination to the elastic peak. <br>Currently, the quasi-elastic peak is fit with a single gaussian, but ideally the fit should account for the helium quasi-elastic, nitrogen <br>quasi-elastic, and hydrogen elastic peaks. JP also suggested checking for temperature fluctuations in the target nose, since at these low <br>temperatures, small fluctuations could have a large effect on the density of the helium. More details can be seen in her slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/melissac/Elastic/Elastic_10_08.pdf here].
| |
| − |
| |
| − | *Ryan
| |
| − | **Gave an update on his study of the Small Angle GDH nitrogen cross sections. Showed an overview of his method and a summary of the <br>saGDH data available. We won't be able to get a ratio of nitrogen/carbon, because the only available carbon data has difference acceptance <br>cuts than the nitrogen data. He showed an example of unfolding the data for 2.1GeV at 6 degrees, using the Bosted model for the lowest <br>energy spectrum in the unfolding. Karl suggested checking the effect of changing the central energy of the model. To get an experimental, <br>unfolded cross section, the difference between the unfolded and radiated interpolated spectrum is applied to the saGDH data. He is using the<br> difference method, as opposed to the ratio method, because the cross section gets close to zero at some points. He also discussed his method <br>of error propagation. Based on conversations with Vince, he starts with a 6% systematic, and combines this with contributions from the elastic <br>tail subtraction and inelastic unfolding. The raw statistical error is scaled using the ratio of the unfolded and inelastic radiated cross sections. <br>To tune the Bosted model, he is trying to find one set of parameters that describe the saGDH data. JP pointed out that there is a visible difference <br>between the model and data at the quasi-elastic peak. It's possible the 2MeV binning is too fine; Ryan will look at the 10 MeV bin data to see if <br>it smooths out the peak. More details can be seen in his slides [https://userweb.jlab.org/~rbziel/Weekly_Meetings/g2p_100814.pdf here].
| |
| − |
| |
| − | *Pengjia
| |
| − | **Is working on studying the effect of different acceptance cuts on the physics asymmetry. For each variable (x, y, theta, phi), he split the <br>distribution into several regions and compared the asymmetry in each region. JP suggested splitting each variable into equal regions statistically <br>instead of equal regions in size. For now, the dilution factor can be left out, and can be applied later when dilution factor analysis is complete. <br>His slides can be seen [http://hallaweb.jlab.org/experiment/g2p/collaborators/pzhu/10082014/asym_20141008.pdf here].
| |
| − |
| |
| − | *Chao
| |
| − | **Gave an update on optics analysis, specifically the y calibration using the target chamber upstream window. Last time he showed a first <br>iteration of the calibration using events from only one large hole in the sieve slit. For the second iteration, he included any possible events from <br>the target and the aluminum window. In addition, he added a focal plane cut to make it easier to distinguish between the sieve holes. The results <br>from the second iteration look pretty good, so for the LHRS calibrations he will stop here for now. The RHRS straight through calibration (with good <br>septum) is completed, so he will start on the longitudinal field setting for the RHRS. More details can be seen in his slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/chao/20141008/Chao_WeeklyMeeting_10082014.pdf here].
| |
| − |
| |
| − | *Jie
| |
| − | **Gave a quick update on the energy loss model for g2psim. The main update is that the Landau distribution used for the ionization model should <br>be Landau(x,ε) instead of Landau(x,4ε). He will give more details next week. His slides can be seen [http://hallaweb.jlab.org/experiment/g2p/collaborators/jie/2014_10_08_simulation/Simulation_update_2014_10_08.pdf here].
| |
| − |
| |
| − |
| |
| − | '''General Discussion:'''
| |
| − | *A room has been booked for the collaboration meeting on November 14th. Kalyan will set up a formal registration for the meeting.
| |
| − |
| |
| − |
| |
| − | ==10/1/2014==
| |
| − |
| |
| − | Present: JP, Chao, Jie, Pengjia, Min, Kalyan, Jixie, Melissa <br>
| |
| − | By Phone: Moshe, Toby, Ryan, Ellie, Karl<br>
| |
| − |
| |
| − |
| |
| − | '''Feature Presentations:'''
| |
| − |
| |
| − | *Toby
| |
| − | **Gave an update on dilution analysis. His current method involves building the total background yield from dilution runs, which are scaled <br>appropriately to match the radiation lengths between runs. To determine the overall systematic uncertainty, contributions come from the <br>packing fraction and the scaling factor gamma, which is the radiation length/nucleon scaling factor for scaling carbon dilution runs to <br>nitrogen. The scaling parameters alpha and beta, which are determined using simulation with the Bosted model, may also contribute to the <br> overall systematic. The results for the dilution factor (for the 3.3 GeV setting) seem reasonable but have a large uncertainty currently. He <br>also described a possible new method, which has been used previously for the RSS and SANE experiments. In this method, the yields are <br>determined from simulation, where the packing fraction value is an input. In this method, some of the systematics will cancel out in the <br>ratio used to determine the dilution factor. The downside to this method is that it requires the ratio of the simulation/data to be <br> kinematically independent. JP suggested trying to improve this method to rely less on the model. More details can be seen in his slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/toby/g2p%20meetings/10.01.14.pdf here].
| |
| − |
| |
| − | *Min
| |
| − | **Gave an update on matching focal plane data in SNAKE. Her goal is to match the simulation results and focal plane data at the "virtual <br>plane", which is located at the entrance of Q1. This location is chosen so that changes can be applied in the septum region, not at the HRS.<br>She showed the comparison of simulation with data for each sieve hole before and after applying the first order fit. There was much discussion <br>on how to do the fit; Jixie suggested fixing the parameters a2/b2 to begin with, then tune them during the second iteration and JP suggested <br>fitting the offset first. There was also some discussion on how to determine the chi-squared value, specifically whether chi-sqared can be <br>minimized in y and phi at the same time, or whether they should be minimized separately. Jixie and Min will discuss this more offline. More <br>details can be seen in her slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/mhuang/10012014/10012014.pdf here].
| |
| − |
| |
| − |
| |
| − | '''General Discussion:'''
| |
| − | *Based on the results of the poll, November 14th is the best day for a collaboration meeting. Each student will give a summary of analysis <br>
| |
| − | progress (~30 minutes) and there will be time for discussion of thesis topics.
| |
| − |
| |
| − |
| |
| − | ==9/24/2014==
| |
| − |
| |
| − | Present: JP, Chao, Jie, Pengjia, Min, Kalyan, Jixie, Melissa <br>
| |
| − | By Phone:Toby, Ryan, Ellie, Karl<br>
| |
| − |
| |
| − |
| |
| − | '''Feature Presentations:'''
| |
| − |
| |
| − | *Pengjia
| |
| − | **Gave a summary of BPM calibrations for entire experimental run. The best situation for calibrations is for data taken between May 3-7, which <br>includes some optics and production data. For runs taken during this time period, the average beam position and angle is 1mm and 1.1 mrad,<br>respectively. The biggest uncertainties are seen in data taken between March 29-31 and April 26-30. During March 29-30, both production and <br>optics data was taken, and the calibration became worse due to large uncertainty in the pedestal. During April 26-30, only production data was<br> taken and the calibration of BPM B had to be done using BPM A and harp data. JP asked how reliable these uncertainties are; Chao said that optics <br>data can be used to try to reconstruct the beam position, as a cross check, but he is not sure of the uncertainty of this method. The run-by-run <br>uncertainties are available in the mysql database. For next time, he will compile a table of contributions to the systematic uncertainty. More details <br>can be seen in his slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/pzhu/09242014/bpm_summary2.pdf here].
| |
| − |
| |
| − | *Ryan
| |
| − | **Showed a systematic error study for inelastic radiative corrections. He wanted to do a sanity check of his method to unfold/radiatively correct the <br>nitrogen data. He started with the Bosted model, which he radiated using SAGDH settings. He then unfolded/radiatively corrected this model, and <br>used the result to compare to the original Bosted model. In radiating the model, he didn't average over the scattering angle at all, and used 3MeV as <br>the value for Delta-E. To radiatively correct this model, it is not possible to directly unfold the equation to get an experimental Born XS, instead he <br>must use an iterative procedure. He showed a comparison of the Bosted model, the radiated model, and the unfolded model. The ratio of the Bosted <br>model compared with the radiated-then-unfolded model agree at low nu to ~1-3%. At higher nu the disagreement becomes larger, but it is never <br>more than 5%. This is good evidence that his method works, so going forward he will start to unfold the SAGDH data and see if he can tune the Bosted <br>model to match the SAGDH data set. More details can be seen in his slides [https://userweb.jlab.org/~rbziel/Weekly_Meetings/g2p_092414.pdf here].
| |
| − |
| |
| − |
| |
| − | '''General Discussion:'''
| |
| − |
| |
| − | *Pengjia will be at JLab for 3 months. We should have another discussion soon about analysis tasks for students as some projects start to finish up.
| |
| − | *Will we try to have a collaboration meeting in mid November. Kalyan has set up a Doodle Poll to select a date - please respond!
| |
| − |
| |
| − |
| |
| − | ==9/17/2014==
| |
| − |
| |
| − | Present: JP, Kalyan, Min, Jie, Chao, Jixie, Melissa <br>
| |
| − | By Phone:Toby, Ryan<br>
| |
| − |
| |
| − |
| |
| − | '''Feature Presentations:'''
| |
| − |
| |
| − | *Melissa
| |
| − | **Gave an update on packing fraction analysis. As was suggested previously, the differing radiation lengths between the dummy and production runs<br> needed to be accounted for. Following the method previously described by Toby, the he4 cross section was radiated using two different radiation <br>thicknesses, one that matched the empty run and one that matched the production run. The ratio of these two cross sections is then used to scale the <br>yield from the dummy run. The scaling factor was larger than expected, most likely due to the fact that the "radcor" program was used to radiate the <br>he4 cross section, and is not meant for elastic radiative corrections. Using this scaling factor, the value of the packing fraction is 0.432. The uncertainty <br>is still large (0.045). This includes a contribution from the difference between the sum and fitting method used to get the area of the peaks. Since the fit <br>is only used to determine the level of contamination, JP suggested that it shouldn't be included directly in the uncertainty. He also suggested that, in the <br>fit of the production run, using one gaussian peak to fit the the second peak may not be a good approximation, since the second peak contains <br>contributions contributions from hydrogen elastic, nitrogen quasi-elastic and helium quai-elastic. More details can be seen in her slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/melissac/Elastic/Elastic_9_17.pdf here].
| |
| − |
| |
| − | *Jie
| |
| − | **Gave an update on the energy loss model used in g2psim. He showed several comparisons of simulation results with data using different ionization<br> models. He showed a simulation results using the ionization model from geant4 combined with the bremsstrahlung model from g2psim, compared to <br>results using the SAMC energy loss model. There is a shift between the two results, which may result from using the mean value vs the most probable <br>value of the distribution. Comparing the simulation results with data, the combination of the SAMC ionization model with the SAMC bremsstrahlung <br>model seems to match best with the data. One update from last time, instead of using data from all sieve holes, he cut on just the center sieve hole. He <br>showed the step-by-step energy loss process (from SAMC), and tried switching the order to see the effect on the results. JP pointed out that the 3 <br>middle steps actually happen simultaneously, so breaking them into steps is an approximation. More details can be seen in his slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/jie/2014_09_16_simulation/Simulation_update_2014_09_17.pdf here].
| |
| − |
| |
| − | *Chao
| |
| − | **Gave an optics status update, specifically a revision of the y-target calibration. Using the beam position scan isn't ideal; since we only took data at <br>dp=0%, the calibration will only work for a small dp range. Jixie results (using geant4) suggest that the upstream window of the target chamber has <br>some acceptance by the Q1 entrance. Since they have seen something upstream in the optics data, he will try to use this data to do the y-target <br>calibration. This result will be more reliable, as it will take all dp settings into account. He identified the data from the window, and used a vertex cut <br>to select them. In each setting, one hole was selected to do the calibration. The calibration result was compared to the known location of the sieve <br>hole. There was good agreement, which suggests the method is working. He is currently on figuring out how to check that the data is actually <br>coming from the upstream window. More details can be seen in his slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/chao/20140917/Chao_WeeklyMeeting_09172014.pdf here].
| |
| − |
| |
| − |
| |
| − | ==9/10/2014==
| |
| − |
| |
| − | Present: Chao, JP, Jie, Jixie, Kalyan, Melissa <br>
| |
| − | By Phone: Pengjia, Toby, Ryan, Ellie<br>
| |
| − |
| |
| − |
| |
| − | '''Feature Presentations:'''
| |
| − |
| |
| − | *Ryan
| |
| − | **Gave an update on using SAMC to compare the Bosted model to SAGDH nitrogen cross sections. SAMC can include both energy loss and inelastic <br>radiative corrections, which makes it the best comparison to the SAGDH cross sections. However, the radiative corrections take a long time to run, <br>so it may not be worthwhile. To test the results of SAMC, he threw 10M events for each momentum setting, but did not turn on energy loss. He <br>compared this to his previous method of averaging the Bosted model result over the scattering angle. The ratio of the two methods is close to 1, <br>suggesting that both methods give similar results. He also did the same comparison, but first radiating SAMC/angle averaged Bosted model, (see <br>slide for equations). There was some discussion on whether this is the proper method to apply these corrections, but it seems that Ryan's method is <br>consistent with what was done previously. Of the two methods, Ryan concluded that the SAMC method isn't any better than his previous method, so <br>it is not worth the extra time it takes to run. JP suggested checking how much the scattering angle varies over the length of the target; if it is linear, <br>than using the average is a good approximation, but this may not be the case. Since there is no SAGDH carbon data that matches our kinematics (that <br>has been analyzed), we won't be able to do a comparison of nitrogen/carbon. Ryan plans to nail down the Bosted model so that it can be used instead; <br>he will scale the Bosted model to match SAGDH nitrogen data, do the same with the SAGDH carbon data, then use the ratio of these to translate the <br>results to our data. More details can be seen in his slides [https://userweb.jlab.org/~rbziel/Weekly_Meetings/g2p_091014.pdf here].
| |
| − |
| |
| − |
| |
| − | ==9/3/2014==
| |
| − |
| |
| − | Present: Chao, Kalyan, Jie, Min, JP, Jixie, Melissa <br>
| |
| − | By Phone: Pengjia, Toby, Ryan, Ellie, Karl, Alexandre<br>
| |
| − |
| |
| − |
| |
| − | '''Feature Presentations:'''
| |
| − |
| |
| − | *Toby
| |
| − | **Gave an update on dilution analysis. His previous method for scaling carbon data to the Bosted nitrogen model had some issues; it left a large gap<br>at the delta resonance, the yield was not continuous at higher values of nu (which is most likely an acceptance issue), and he assumed a constant<br>scaling factor in nu. In his updated method, he ran the Bosted simulation for both carbon and nitrogen, and used the ratio between the two models<br>as a bin-by-bin scaling factor for carbon. He also showed a method for matching the radiation lengths of the different materials. To match the<br>radiation lengths of two different targets, for example carbon and production, he produces two radiated carbon models. The first has the radiation<br>length of the carbon target, while the second uses the radiation length of the production target. The ratio of these two models is the scaling factor to<br> matchthe radiation length of carbon to production. JP suggested building both radiation lengths into the model, to make the process one step versus <br>two. Toby will look into the difference in results for the two methods. The preliminary results for the dilution factor are smaller than expected, but he <br>is still working on determining the uncertainty. More details can be seen in his slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/toby/g2p%20meetings/09.03.14.pdf here].
| |
| − |
| |
| − | *Min
| |
| − | **Working on matching focal plane data to SNAKE. To accomplish this, she first divides the transport functions into two steps; the target to the virtual <br>plane, then the virtual plane to the focal plane. She focused on tuning the functions that included contributions from the septum field, and worked on <br>aligning the center sieve hole. The results look good, so for next time she will work on aligning the other sieve holes. More details can be seen in her <br>slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/mhuang/09032014/09032014.pdf here].
| |
| − |
| |
| − | *Jie
| |
| − | **Gave an update on the energy loss model. Last time he showed a comparison of the ionization models used in geant4 and SAMC. This time, he looked <br>at how internal and external Bremsstrahlung are included in SAMC and the g2psim package. Ryan suggested looking at the size of the contribution from <br>internal/external Bremsstrahlung to the overall energy loss, as he found it was much smaller than the contribution from ionization. Jie showed a comparison <br>between data and simulation including two different ionization models; in one case (geant4 model) the simulation was too narrow compared to the data, in <br>the other case (SAMC model), the simulation was wider than the data. Jixie suggested to only look at the data from one sieve hole when comparing with <br>simulation, as opposed to all the sieve holes. More details can be seen in Jie's slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/jie/2014_09_03_simulation/Simulation_update_2014_09_03.pdf here].
| |
| − |
| |
| − |
| |
| − | ==8/27/2014==
| |
| − |
| |
| − | Present: Min, JP, Jie, Jixie, Melissa <br>
| |
| − | By Phone: Moshe, Pengjia, Toby, Ryan, Ellie, Karl, Alexandre<br>
| |
| − |
| |
| − |
| |
| − | '''Feature Presentations:'''
| |
| − |
| |
| − | *Moshe
| |
| − | **Gave an update on dilution analysis with GEp data. GEp needs an accurate dilution factor in the hydrogen-elastic region, which is tough to achieve <br>since there is little data and few good models for nitrogen and helium in the quasi-elastic region. One solution is to use small angle GDH data and <br>extrapolate to different kinematics. The second solution is to use carbon data, if it is possible to scale the carbon data to nitrogen in the quasi-elastic <br>setting. He showed results from simulation comparing carbon, nitrogen and helium. In the Bosted model, the quasi-elastic region of carbon and <br>nitrogen are scaleable, while in the QFS model, carbon, nitrogen and helium are all scaleable. In the elastic region, he scaled carbon and nitrogen data <br>to the same number of elastic events. With both models, this made a good match at the quasi-elastic region. Following this same procedure for <br>comparing helium and nitrogen, however, did not give a good match in the quasi-elastic region. Based on his simulation, the contribution from helium <br>is relatively small in both models. More details can be seen in his slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/moshe/dilution_friedman_081714.pdf here].
| |
| − |
| |
| − | *Melissa
| |
| − | **Gave an update on extracting the packing fraction using data. She updated her previous method, which included input from simulation, to include <br>only production/dilution runs. This method assumes a uniform acceptance throughout the target cell, which can be corrected for once the acceptance <br>analysis is complete. Toby pointed out that helium and nitrogen have different radiation lengths, which will need to be accounted for. The resulting <br>value for the packing fraction agrees with the expectation, but with a large uncertainty (~10%). She will work on reducing this uncertainty, as well as <br>extracting the packing fraction for other materials/settings. More details can be seen in her slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/melissac/Elastic/Elastic_8_27.pdf here].
| |
| − |
| |
| − | *Ryan
| |
| − | **Gave an update on using SAMC to generate nitrogen cross sections. He got the version of SAMC setup for SAGDH experimental conditions from Vince,<br> and used the Bosted model as the cross section model. An advantage of using SAMC is that it can include energy loss corrections and inelastic radiative <br>corrections. This will probably allow for the best comparison between the Bosted model and SAGDH nitrogen cross sections. However, the radiative <br>take a long time to run, so it may not be worthwhile. For next time, he will work on comparing the SAMC results for the XS with his method for averaging <br>the cross section over the acceptance as well as the SAMC radiative corrections with his method of radiative corrections. More details can be seen his <br>slides [https://userweb.jlab.org/~rbziel/Weekly_Meetings/g2p_082714.pdf here].
| |
| − |
| |
| − |
| |
| − | ==8/20/2014==
| |
| − |
| |
| − | Present: Kalyan, Min, JP, Jie, Jixie Melissa <br>
| |
| − | By Phone: Toby, Ryan, Ellie, Karl, Pengjia, Moshe, Alexandre<br>
| |
| − |
| |
| − |
| |
| − | '''Feature Presentations:'''
| |
| − |
| |
| − | *Jie
| |
| − | **Gave an update on the energy loss model being used in the g2psim package. Previously, he showed a discrepancy in the delta when comparing<br> data with simulation results. He was able to better match the data with simulation by using a different ionization model. The old ionization model<br>(taken from Geant 4) used a continuous energy loss, with fluctuations, below an energy threshold. Above the threshold, the energy loss is simulated <br>by the explicit secondary particles. The updated ionization model (taken from SAMC) assumes the probability distribution of energy loss by ionization <br>is a Landau distribution. He showed a comparison of the energy loss from ionization for g2psim and the SAMC model. If g2psim includes continuous <br>energy loss, but not delta-ray production, it does not match with the model. But, if g2psim includes 1 delta-ray production along with continuous energy <br>loss, it agrees much better with the model. More details can be seen in his slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/jie/2014_08_20_simulation/Simulation_update_2014_08_20.pdf here].
| |
| − |
| |
| − | *Min
| |
| − | **Gave an update on her acceptance study. Last time, she showed that there is some discrepancy between the peaks (in delta, theta and phi variables), <br>between data and simulation. She showed comparisons of the data and simulation with the "true" locations, and a sanity check of the transport functions, <br>which seem to fit our requirements for the resolution. There was some discussion about whether or not the exit/entrance windows (made of kapton and<br> titanium) were included in the energy loss model. Jie says they are both included right after the sieve slit. In the simulation, Min modified the VDC resolution <br>to be 0 and made the x-tg inputs the same, and saw good agreement between the data and simulation. However, when the VDC resolution was included back <br>in, she again saw a discrepancy between the data and simulation. For next time, she will also include focal plane variables. More details can be seen in her <br>slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/mhuang/08202014/08202014.pdf here].
| |
| − |
| |
| − | *Jixie
| |
| − | **Simulated optics events scattering from the target chamber window to see if they make it to the focal plane. He used a 1cm raster with no target field, and <br>found that events originating from the target chamber entrance window do indeed make it to the focal plane. The ratio of events from the chamber window to <br>events from the target is 3.6%. More details can be seen in his slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/jixie/20140820_SCWin_Sim/G2P_SC_win_elas.pdf here].
| |
| − |
| |
| − |
| |
| − | ==8/13/2014==
| |
| − |
| |
| − | Present: Kalyan, Min, JP, Jixie Melissa <br>
| |
| − | By Phone: Pengjia, Moshe, Alexandre, Chao <br>
| |
| − |
| |
| − |
| |
| − | '''Feature Presentations:'''
| |
| − |
| |
| − | *Melissa
| |
| − | **Gave an update on packing fraction analysis. In her current method to extract the packing fraction, the g2psim package is used to determine a value<br> for the cross section of different materials (nitrogen, hydrogen and helium). She showed an updated comparison of the simulation with data. The results <br>look better, but there are still some problems (simulation needs to be weighted by cross section, for example). There were also some questions raised <br>about the fitting routine used to fit the data; the Landau-Gaussian convolution fit does a good job of fitting the elastic peak, but not the radiative tail. Once <br>radiative corrections are included, the values of Ax (normalization factor used in packing fraction equation) will most likely change; the contribution from <br>Nitrogen should be larger. A suggestion was made to not use cross sections from simulation as input, but rather just use yields from data instead. She will <br>try this for next time. More details can be seen in her slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/melissac/Elastic/Elastic_08_12.pdf here].
| |
| − |
| |
| − | *Pengjia
| |
| − | **Posted yields calculated from pass-3 rootfiles to the ELog. The unusual shape seen in some cases is most likely due to acceptance. There is still a <br>discrepancy in the yields between different runs for some settings.
| |
| − |
| |
| − |
| |
| − | ==8/6/2014==
| |
| − |
| |
| − | Present: Min, JP, Jie, Jixie, Melissa <br>
| |
| − | By Phone: Chao, Toby, Ryan, Ellie, Pengjia, Alexandre, Karl<br>
| |
| − |
| |
| − |
| |
| − | '''Feature Presentations:'''
| |
| − |
| |
| − | *Min
| |
| − | **Gave an update on acceptance studies. In the simulation, the events are generated uniformly over the area of the raster, so she did a study to check<br> the beam distribution for the data. Within the raster pattern, she divided each event by the XS (which was calculated event by event using the Bosted <br>model). By doing this, the 2D plot of the raster pattern appears to be uniform. She also showed the corresponding 1D plots of beam x and beam y; <br>the beam y distribution appears to be flat while the beam x distribution has a slope on the left side. She also used the same procedure, but divided by <br>the Mott cross section, and saw similar results.
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| − | **Also showed a comparison between data and simulation for a 2.2 GeV optics run with 0T target field. Last time, she showed a discrepancy between the <br>two. For this time, she updated the simulation to include a different ionization model and used the same energy loss used in optics calibrations. Using the<br>updated simulation, there is much better agreement between data and simulation. JP commented that we should make sure we understand where the <br>discrepancy came from in order to choose the best model, not just choosing the one that matches the data best, so as not to introduce bias to the analysis. <br>For next time, Jie will show a comparison of the two models. More details can be seen in Min's slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/mhuang/08062014/08062014.pdf here].
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| − |
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| − | *Ryan
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| − | **Gave an update on his comparison of the nitrogen XS from SAGDH data with the Bosted model. The raw XS results from SAGDH now include a multi-track<br>analysis study. To find the best scaling factor to match the data with the model, he uses a reduced chi-squared method. Vince gave him the results of an <br>elastic tail Monte Carlo used to simulate the acceptance, which also includes the "punch through" correction. Although this can't be compared to older SAGDH <br>nitrogen analysis (since the acceptance cuts have changed), but he can use the results to compare Vince's method to his. He found that his method is consistent <br>with the Monte Carlo results, and the small difference (which is a maximum of 5% in the tail), is only ~1% difference in the subtracted XS. He showed the <br>comparison of the XS from data with the Bosted for all the SADGH kinematics; each setting has a different scaling factor and shift in nu. The shift in nu is quite <br>large (6-16 MeV). To understand the energy shift, Karl suggested trying to reproduce the shift with a change in scattering angle. JP also suggested making the <br>outgoing thickness of the cell a parameter, as a small change could have a large effect. There was a question of what was included in the radiating of the Bosted <br>model; for next time he will show a comparison of the model before and after radiation. He will also work on full inelastic radiative corrections for the SAGDH data <br>so that he can extract the Born XS, which can then be compared to the Bosted model. More details can be seen in his slides [https://userweb.jlab.org/~rbziel/Weekly_Meetings/g2p_080614.pdf here].
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| − |
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| − | ==7/30/2014==
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| − |
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| − | Present: JP, Melissa <br>
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| − | By Phone: Toby, Ryan, Ellie, Pengjia, Alexandre<br>
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| − |
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| − |
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| − | '''Feature Presentations:'''
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| − |
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| − | *Toby
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| − | **Gave an update on dilution analysis. Last time, he showed a comparison of yields from data with the prediction from the Bosted model, and then<br> scaled the model by computing an "acceptance factor". This time, he did the same thing for the 2.2 GeV settings, but found that the same acceptance <br>factor did not work for all energy settings, due to the fact that the scattering angle is different for each energy setting. Since the scattering angle is <br>dependent on nu, the acceptance factor will have to be momentum dependent. He showed plots of the scattering angle vs nu for the 3.3 and 2.2 GeV <br>settings, and fit the distribution with an exponential function (see Jixie's elog post 49 for more details). The parameters from the fit can then be used <br>to calculate the scattering angle for each momentum value in the Bosted model. This method looks promising, but there appears to be a suppression <br>of the delta in our data that does not match with simulation. From this, he will be able to extract a rough value for the dilution factor, which should be <br>available soon. More details can be seen in his slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/toby/g2p%20meetings/07.30.14.pdf here].
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| − |
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| − |
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| − | ==7/16/2014==
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| − |
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| − | Present: Jie, Min, Jixie, Melissa <br>
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| − | By Phone: Toby, Ryan, Ellie, Karl, Pengjia<br>
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| − |
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| − |
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| − | '''Feature Presentations:'''
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| − |
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| − | *Min
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| − | **Working on an acceptance study for the 1st and 3rd septum settings. For looking at data from optics runs, she applies focal plane and target cuts to <br>get rid of junk events and select only elastic events. For this time, she updated the beam cut to match what Chao used for the optics calibrations. For <br>the simulation, elastic events are generated according to the beam position in the cut. For the dilution run (empty run), the procedure is similar, but she <br>applies a target plane graphical cut on the data instead of a focal plane cut. To simulate the empty run, she used the same target plane cuts that were <br>applied to the data, but generated events in an ellipse. For both the optics and dilution runs, the theta and phi variables agree reasonably well, but there <br>is a discrepancy in the dp variable. For next time, she will look into this discrepancy as well as look at the other settings. More details can be seen in her <br>slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/mhuang/07162014/07162014_acceptance.pdf here].
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| − |
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| − | *Ryan
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| − | **Showed a comparison of the Bosted Model with SAGDH data. He generated the nitrogen cross section using the Bosted model for each of the SAGDH <br>kinematics, then he can radiate the model for each reconstructed scattering angle, within acceptance. In order to compare to SAGDH data, he averaged <br>over the scattering angles. Previously, he tried to determine a single scaling factor for all the kinematic settings, this time he chose different scaling <br>factors for each setting to best match the data. For each setting, he found that averaging over the scattering angle decreases the scaling factor by about<br>5%. Karl suggested using another data set to compare, possibly using our data to extract the carbon cross section. For the future, he will consider the <br>effect of the punch through from the collimators, which effectively increases the radiation length. He will also look at the SAGDH data for <br>two settings that he hasn't looked at before (9deg/2234 MeV and 9deg/3319 MeV), among other things. More details can be seen in his slides [https://userweb.jlab.org/~rbziel/Weekly_Meetings/g2p_071614.pdf here].
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| − |
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| − | *Jie
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| − | **Gave an update on packing fraction analysis. Last time, he used runs from the 2nd septum setting (40-32-16). Since the SNAKE model is not quite <br>ready for this setting yet, this time he analyzed a set of runs from the 2.2 GeV, 5T, longitudinal setting, which uses the 3rd septum setting (40-00-16). <br>He applied a 2D graphical cut to select elastic events, though Karl pointed out that this isn't a 100% pure elastic sample, as there could be a tail underneath <br>the peak. Using this set of runs, he determined the packing fraction to be 0.51, with an uncertainty of 7.6%. The largest contribution to this uncertainty <br>comes from the uncertainty of the absolute beam position. Ellie suggested showing a comparison of the XS models (that are used as input) to data to test <br>how well they match, which Jie will work on for next time. More details can be seen in his slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/jie/2014_07_15_simulation/Simulation_update_2014_07_15.pdf here].
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| − |
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| − |
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| − | '''General Discussion:'''
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| − | *Ryan and Toby have circulated their abstracts for the GRC. Please provide feedback!
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| − |
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| − | ==7/9/2014==
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| − |
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| − | Present: Jie, Min, Melissa <br>
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| − | By Phone: Toby, Ryan, Ellie, Karl, Pengjia<br>
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| − |
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| − |
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| − | '''Feature Presentations:'''
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| − |
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| − | *Melissa
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| − | **Showed updates to her method to extract the packing fraction. Biggest change is that the input for cross sections for the various materials will be <br>determined using g2psim. Also, different runs, which have consistent beam position information, were used for the analysis. To test the conditions of <br>the simulation, she showed a comparison between simulation and data for a helium dilution run. The parameters of the simulation will need to be <br> adjusted, as there is a clear discrepancy between the simulation and data. Using the updated values for the XS, the value for the packing fraction <br>increases slightly, but will likely change as the simulation results are improved. More details can be seen in her slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/melissac/Elastic/Elastic_7_9.pdf here].
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| − |
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| − |
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| − | ==7/2/2014==
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| − |
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| − | Present: Kalyan, JP, Chao, Jie, Min, Jixie, Melissa <br>
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| − | By Phone: Toby, Ryan, Ellie, Karl, Pengjia, Alexandre<br>
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| − |
| |
| − |
| |
| − | '''Feature Presentations:'''
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| − |
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| − | *Min
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| − | **Working on an acceptance study for the 3rd ("very bad") septum configuration, using a Monte-Carlo simulation. She started with optics and dilution runs, <br> since they have a simple target. Loose cuts were applied to throw away junk events, and to select elastic events. She showed a comparison of simulation vs <br>data; for the 1.7 GeV setting (empty cell run), the simulation results are smaller than the data, but for the 2.2 GeV setting, the simulation is larger than the data. <br>Also, the shape <br>of the phi distributions from simulation do not match the data. JP suggested this could be a result of the momentum calibration or energy<br> loss being slightly off. For next time, she will look at a setting with the "good" septum configuration. Also, she will look into the delta discrepancy for the elastic<br>setting and will work on tuning the apertures for theta/phi matching (boundary matching). Additionally, the simulation needs to be updated to reflect the true <br>shape of the beam, which is elliptical, not circular. More details can be seen in her slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/mhuang/07022014/07022014_acceptance.pdf here].
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| − |
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| − | *Jie
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| − | **Gave an update on simulations. Last time he showed an update to the event generator. This time, he wanted to check the difference in the phase space <br>density. He showed a comparison of the density function vs theta for two different values of phi-target; the difference between them was very small. He also <br>showed an update of the packing fraction uncertainty. He determined the relative uncertainty to be 7.19% for a 1mrad shift in the scattering angle. He showed <br>the beam information for the 3 runs being used in the packing fraction calculation (a production, dummy and carbon run), and the beam position seemed <br>consistent for all 3 runs. JP expressed concern that this beam position calibration is too good, and doesn't reflect the actual beam conditions. For next time, <br>Jie will show the beam position event by event. More details can be seen in his slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/jie/2014_07_01_simulation/Simulation_update_2014_06_30.pdf here].
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| − |
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| − | *Ryan
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| − | **Showed a comparison of small angle GDH data with the P. Bosted model. He generated a nitrogen cross section using the Bosted model, then inelastically <br>radiated it so that it could be compared with the SAGDH data (the SAGDH data already has the elastic tail subtracted). He showed comparisons for several <br>different energy settings, in all cases the Bosted XS had been scaled down by 30%. For next time, he will check the effect of averaging over the scattering angle; <br>the Bosted model is calculated at one scattering angle, while the SAGDH data is broken up into multiple bins. He will also repeat this study using QFS and do full <br>inelastic radiative corrections on the SAGDH data in order to extract the Born cross section. More details can be seen in his slides [https://userweb.jlab.org/~rbziel/Weekly_Meetings/g2p_070214.pdf here].
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| − |
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| − | *Toby
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| − | **Gave an update on dilution analysis. Last time there was a question about using the radiated vs unradiated Bosted model, this time he showed a comparison <br>of the two. He also updated his method to extract the dilution factor. The number of counts is defined in terms of the acceptance, luminosity, cross section and <br>time. This way, the yield scales by the acceptance, which can be assumed to be the same for each run. The yield from carbon (and helium) can be calculated using <br>dilution runs, which can then be related to a cross section using the P. Bosted model. Using the acceptance scaling factor, he can relate the nitrogen and carbon <br>yields. Using the data from the 3.3 GeV setting, the scaling factor ("a") that relates carbon to nitrogen is 1.17, but this may need to be adjusted regions (quasi-<br>elastic, delta, beyond the delta, etc.) More details can be seen in his slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/toby/g2p%20meetings/07.02.14.pdf here].
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Each student gave a short update on their analysis projects since the last collaboration meeting on November 14th:
