# Difference between revisions of "G2p Analysis Minutes"

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+ | ==5/7/2014== | ||

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+ | Present: Kalyan, Chao, Jie <br> | ||

+ | By Phone: Toby, Ryan, Ellie, Pengjia, Alexandre<br> | ||

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+ | |||

+ | '''Feature Presentations:''' | ||

+ | |||

+ | *Pengjia: | ||

+ | **Gave an update on determining the uncertainty of BPM calibrations. He tested the method to use the rms value for a run range to estimate uncertainty. It was <br>calculated for each run before. With this method the uncertainty of theta angle is ~0.0009rad. A method to calculate the uncertainty in auto-gain mode is also <br>proposed by him. Several runs with relatively stable beam position were used to get the maximum beam position deviation to replace the pedestal uncertainty. <br>The angle uncertainty is ~0.002rad with this method. More details can be found in his slides [http://hallaweb.jlab.org/experiment/g2p/collaborators/pzhu/05072014/bpm_status_20140507.pdf here]. | ||

## Revision as of 13:38, 7 May 2014

Minutes of the weekly analysis meetings

## Contents

- 1 5/7/2014
- 2 4/30/2014
- 3 4/23/2014
- 4 4/16/2014
- 5 4/9/2014
- 6 4/2/2014
- 7 3/26/2014
- 8 3/19/2014
- 9 3/12/2014
- 10 3/5/2014
- 11 2/26/2014
- 12 2/19/2014
- 13 2/12/2014
- 14 2/05/2014
- 15 1/24/2014
- 16 1/15/2014
- 17 1/8/2014
- 18 June-Dec 2013
- 19 Jan-May 2013
- 20 April-Dec 2012
- 21 Jan-March 2012
- 22 July-Dec 2011
- 23 Jan-June 2011

## 5/7/2014

Present: Kalyan, Chao, Jie

By Phone: Toby, Ryan, Ellie, Pengjia, Alexandre

**Feature Presentations:**

- Pengjia:
- Gave an update on determining the uncertainty of BPM calibrations. He tested the method to use the rms value for a run range to estimate uncertainty. It was

calculated for each run before. With this method the uncertainty of theta angle is ~0.0009rad. A method to calculate the uncertainty in auto-gain mode is also

proposed by him. Several runs with relatively stable beam position were used to get the maximum beam position deviation to replace the pedestal uncertainty.

The angle uncertainty is ~0.002rad with this method. More details can be found in his slides here.

- Gave an update on determining the uncertainty of BPM calibrations. He tested the method to use the rms value for a run range to estimate uncertainty. It was

## 4/30/2014

Present: Kalyan, Jixie, Jie, Chao

By Phone: Karl, Toby, Ryan, Ellie

**Feature Presentations:**

- Toby:
- Gave an update on dilution analysis. Normalized Carbon yields of 2.254 GeV setting was calculated. The yields do not match well, probably because of

optics. Karl suggested that some acceptance input might fix this problem. Toby also calculated the 3.350 GeV Carbon yields and compared it with Nitrogen QFS

cross sections to find the scaling factor. Karl suggested to compare the carbon yields with model directly at first. 3.350 GeV dilution factors was also calculated.

The plot showed a huge jump due to the matching problem of the yields in production data. As the next step, he will run the simulation with P. Bosted model

and compare with data. Karl suggested that he could use Vince's data for carbon too. More details can be seen in his slides here.

- Gave an update on dilution analysis. Normalized Carbon yields of 2.254 GeV setting was calculated. The yields do not match well, probably because of

- Chao:
- Gave an update on optics. He showed a table of the first order matrix results from a new fitting which limit the matrix up to the 2nd order. New matrix elements

do not show clear dependence of the septum settings, which is different from the previous result. The offset of the theta and phi matrix is still large in the new

calibration result. He did an extended target correction to remove the theta offset and reduce the high order effect. The correction constants still need to be

improved. Since the first iteration of LHRS optics is almost done, he also suggested that it is a good time to replay the longitudinal production data and check

the optics with data. He will work together with Toby to do this. More details can be seen in his slides here.

- Gave an update on optics. He showed a table of the first order matrix results from a new fitting which limit the matrix up to the 2nd order. New matrix elements

- Jie:
- Gave an update on yield results from simulation. He did the simulation again to study the influence of beam position to the yields. An updated HRS transportation

model with some acceptance cuts was used. However, he still found that the yield would increase when the shift in beam-x became larger. It might be because

the acceptance cuts of this transportation model still need to be tuned and he will start to work on that. More details can be seen in his slides here.

- Gave an update on yield results from simulation. He did the simulation again to study the influence of beam position to the yields. An updated HRS transportation

## 4/23/2014

Present: Kalyan, Chao, JP, Jie, Melissa

By Phone: Toby, Ryan, Karl, Ellie, Pengjia

**Feature Presentations:**

- Ryan:
- Working on radiative corrections to the elastic peak. The goal is to determine the elastic radiative corrections for the small angle GDH nitrogen data,

- Working on radiative corrections to the elastic peak. The goal is to determine the elastic radiative corrections for the small angle GDH nitrogen data,

then compare the XS results to that of a model. To do this he will need to integrate over the elastic peak in the SAGDH data. For the elastic peak, his

calculations match the results from Mo/Tsai. To find the full strength of the elastic peak, he fit the peak with a Gaussian. However, since there are only

4 points in the fit range, the fit is poorly constrained. JP suggested just summing up the channels in the peak, instead of trying to use a fit. As a "sanity

check", Karl suggested finding the strength of the Born peak, determining the elastic radiative tail, then comparing it to his previously determined

correction for the elastic tail. More details can be seen in Ryan's slides here.

- Melissa:
- Looked at the spread in yields for production runs in the 2.2 GeV, 2.5T, transverse setting. She showed an example for the setting where p0 = 1.927

- Looked at the spread in yields for production runs in the 2.2 GeV, 2.5T, transverse setting. She showed an example for the setting where p0 = 1.927

GeV/c, which had a spread of ~15.2%. However, runs taken with different materials should not be compared to each, as the packing fraction could be

significantly different. For this setting, the yields for material eight seem consistent between runs taken on the left and right HRS. The runs taken with

material 7, which were taken several days later, are considerably lower on the RHRS. She will check other momentum settings for this type of behavior.

Her slides can be seen here.

## 4/16/2014

Present: Kalyan, Chao, JP, Jie, Jixie, Melissa

By Phone: Toby, Ryan, Karl, Ellie, Pengjia, Alexandre

**Feature Presentations:**

- Jie:
- Gave an update on yield results from simulation. He varied the beam position at target center to see the effect on the yields for the elastic peak. He

found that, as the shift in beam-x became larger, the yield also became larger. JP suggested that this shift is too large; a shift in beam-x of 5mm causes

the yield to be ~33% larger. Since we have a short target, the shift in x should not affect the scattering angle, at least to first order. It may, however,

affect the acceptance. It's possible something is not correct in the simulation, Jie will look into this. Since the packing fraction runs for this setting do

not agree with each other, he tried extracting the packing fraction using a production run taken around the same time as the dilution runs for this setting.

This way, the beam conditions will be the same for the ammonia/dilution runs. Using two slightly different methods to extract the pf he got results of

pf=0.583 and pf=0.389. More details can be seen in his slides here.

- Gave an update on yield results from simulation. He varied the beam position at target center to see the effect on the yields for the elastic peak. He

- Pengjia:
- Gave an update on determining the uncertainty of BPM calibrations. Included in the calibration constant uncertainty is the harp survey uncertainty, BPMs

survey uncertainty and the BPM resolution for the calibration runs, with 2Hz filter. Included in the BPM survey uncertainty is the pedestal uncertainty, which

uses a 2Hz pedestal rms value. The uncertainty caused by the target field is not included. JP commented that this affects the angle more than the position.

The uncertainty study for the time period in auto-gain mode is not done yet. He is also working on writing up a technote of this analysis. His slides can be

seen here.

- Gave an update on determining the uncertainty of BPM calibrations. Included in the calibration constant uncertainty is the harp survey uncertainty, BPMs

- Min (presented by Chao):
- Gave a summary of work on transport functions. Looking at all the data, only ~6 production runs in the 2.2 GeV, 2.5T, transverse setting were taken with

the "good" (484816) septum configuration. The rest of the runs in this setting have the "bad" (403216) septum configuration. The other four settings were

all taken with the "very bad" (400016) setting. The transport functions are ready to use for all settings except for the 403216 septum configuration. It is not

clear whether the fitting was done for both the left and right HRS, but Chao will check with Min. More details can be seen in her slides here.

- Gave a summary of work on transport functions. Looking at all the data, only ~6 production runs in the 2.2 GeV, 2.5T, transverse setting were taken with

## 4/9/2014

Present: Kalyan, Min, Chao, Melissa

By Phone: Toby, Ryan, Karl, Ellie, Pengjia

**Feature Presentations:**

- Melissa:
- Outlined a procedure for doing a check of the quantity f*Pb*Pt using elastic asymmetries. The prediction for the physics asymmetry can be expressed

in terms of elastic form factor (details of the formalism can be found in C. Crawford thesis, based on the procedure by Donnelly and Raskin). The

parameterization for the elastic form factors is taken from the most recent global fit of proton elastic data (J. Arrington et al.). The elastic asymmetries at

2.2 GeV with 5T magnetic field (both in the longitudinal and transverse configurations) should be large enough for this check. Karl commented that

detector efficiencies should also be accounted for, and that radiative corrections will need to be included as well. More details can be seen in her slides here.

- Outlined a procedure for doing a check of the quantity f*Pb*Pt using elastic asymmetries. The prediction for the physics asymmetry can be expressed

- Ryan:
- Working on radiative corrections for the elastic peak. Previously, he has shown results for radiative corrections for the elastic tail, but now is looking

at corrections for the elastic peak for nitrogen data from Small Angle GDH. The formalism is based on Mo/Tsai, and he is writing the code in c++ from

scratch. The goal is to be able to compare the XS extracted from data to a model. He gave an overview of the theory explaining the different contributions

to the overall correction. He still needs to include a calculation of delta-t, which includes the thicknesses of the different materials in the target, and to

code the "straggling" term. Also, he will work on using a Gaussian fit of SAGDH data to obtain the radiated elastic XS, and will determine the quantity delta-E

for the SAGDH data. More details can be seen in his slides here.

- Working on radiative corrections for the elastic peak. Previously, he has shown results for radiative corrections for the elastic tail, but now is looking

- Min:
- Gave an update on transport functions. Previously, she has shown the forward and backward transport functions between the target and focal plane. Now

she has completed the forward transport functions from the target plane to multiple end-planes along the trajectory of the electron, for the case with the

"good" septum. She also included a diagram of the side and top down view of the trajectory. She will add this transport function to the g2psim package

and will next start working on the transport functions for the other septum conditions. She is leaving next week for China, so she will try to have this done

before she leaves. Her slides can be seen here.

- Gave an update on transport functions. Previously, she has shown the forward and backward transport functions between the target and focal plane. Now

## 4/2/2014

Present: Chao, Kalyan, Min, Jie, Melissa

By Phone: Alexandre, Toby, Ryan, Karl, Ellie, Moshe, Pengjia

**Feature Presentations:**

- Chao:
- Gave an update on optics calibrations. Showed the calibration results for the setting with beam energy of 2.2GeV, 2.5T, transverse target field, and the

2nd septum setting (40-32-16). The central hole has a small offset in phi, but this is not a problem since the effective phi and theta are determined using

and event by event simulation. He also showed a table of the first order matrix results, comparing the two septum configurations both with and without

the target field. The phi matrix elements (P0010 and P0001) for 0T and 2.5T field are comparable, but there is a difference between the different septum

settings (which makes sense!). The theta matrix elements (T0100) do not change much between the septum settings, since the septum doesn't have a large

affect on theta. Next he will work on the extended target correction, as the vertical (x) beam position may cause the offset in theta. He will also work on the

RHRS optics calibrations. More details can be seen in his slides here.

- Gave an update on optics calibrations. Showed the calibration results for the setting with beam energy of 2.2GeV, 2.5T, transverse target field, and the

- Toby:
- Gave an update on dilution analysis. He summarized his method for extracting the dilution factor; first he must define the total background in terms of the

dilution runs. In order to relate the different dilution runs, a scaling method is used to account for the different radiation lengths of the materials. Also, a

scaling factor must determined to scale the carbon yield to the nitrogen yield. To determine the radiative tail for the "empty" dilution run, two methods were

used; using the true radiation length of helium and matching the helium and carbon radiation lengths by extending the helium target length. A ratio is taken

between the two results and is used to scale the radiation length for the empty dilution run to the carbon run. Karl suggested that the yield from helium does

not need to scaled in this way - he and Toby will discuss this more offline. He also showed a comparison between simulation and data for the helium yield.

Currently, he is using Moshe's simulation, which does not include the magnetic field or acceptance. The g2psim package is probably better suited for this study.

More details can be seen in Toby's slides here.

- Gave an update on dilution analysis. He summarized his method for extracting the dilution factor; first he must define the total background in terms of the

- Jie
- Gave an update on simulations. There is a discrepancy in the yields for the packing fraction runs in the 2.2 GeV, 2.5T transverse setting. The fluctuation in

yields seems to be correlated to changes in the beam position. He simulated the yields for three different packing fraction runs and varied the average beam

position and incident angle. While there was some difference seen in the simulated yields as a result of these changes, they did not match the data. That is, the

run with the smallest yield from the data had the highest simulated yield. He will keep working on this and check his results. More details can be seen in his

slides here.

- Gave an update on simulations. There is a discrepancy in the yields for the packing fraction runs in the 2.2 GeV, 2.5T transverse setting. The fluctuation in

- Pengjia
- Gave an update on determining the uncertainty for the beam position calibrations. The calibration constant uncertainty has contributions from the harp survey

uncertainty, bpm survey uncertainty (for each calibration run), and the BPM resolution with 2Hz filter. The overall uncertainty for the center position also contains

BPM survey uncertainty (for each run) and uncertainty due to the pedestal. The uncertainty caused by the target field is not included. He also showed some

specific uncertainty results for a few different run periods (details can be seen in his slides). For the runs that were taken with the autogain setting (runs taken before

March 30th), there is no way to get the pedestal uncertainty, so he used one value for all the runs. He is working on writing up the details of this analysis in a

technote, which he will send out soon. His slides can be found here.

- Gave an update on determining the uncertainty for the beam position calibrations. The calibration constant uncertainty has contributions from the harp survey

## 3/26/2014

Present: Chao, Jie, Min, Melissa

By Phone: Toby, Ryan, Moshe Pengjia, Karl, Ellie

**Feature Presentations:**

- Melissa:
- Gave an update on the variance in scattering angle. The discrepancy in yields seems to be correlated to changes in the beam position. She showed

a couple plots showing the change in the scattering angle an incident angle for a set of runs in the 2.2 GeV, 2.5T setting. Next she will try to understand

the effect of the change in scattering angle on the yields (using a simulation), and developing a correction for this. Her slides can be seen here.

- Gave an update on the variance in scattering angle. The discrepancy in yields seems to be correlated to changes in the beam position. She showed

- Min:
- Gave an update on the status of optics calibrations. Of the 8 total LHRS settings, 5 are done and 1 is in progress. Min is working on the setting with beam

energy of 1.7 GeV, 2.5T transverse target field. This setting has the "bad" septum configuration (40-00-16) and a full delta scan on the LHRS. The results of

the angle and momentum calibration look good. Next she will look at beam position scan data for this setting, then move on to the remaining LHRS settings.

More details can be seen in her slides here.

- Gave an update on the status of optics calibrations. Of the 8 total LHRS settings, 5 are done and 1 is in progress. Min is working on the setting with beam

- Pengjia:
- Gave an update on BPM calibrations, specifically the issue of the fluctuating pedestals. He looked at one run, where the pedestal value is different for the first

and last quarter of the run. If the beam position for these two regions using the pedestal for that region, there is a large discrepancy between the position at

BPMA and BPMB. If the position is calculated using the same pedestal for both regions (the pedestal for the last quarter of the run), then the discrepancy between

the two BPMs is much smaller. One possible explanation is that the pedestal fluctuation for this period came from the source after the BPMs receiver amplifier, but

not before the ADC. Overall, most of the runs now have calibrated beam position information. There are some runs where the happex ADC was saturated, so he

will have to determine the calibration with the fastbus ADC. He is currently working on determining the uncertainty and writing up this analysis in a technote. More

details can be seen in his slides here.

- Gave an update on BPM calibrations, specifically the issue of the fluctuating pedestals. He looked at one run, where the pedestal value is different for the first

## 3/19/2014

Present: Chao, Jie, Min, Melissa

By Phone: Pengjia, Ellie, Karl

**Feature Presentations:**

- Chao:
- Gave an update on status of optics calibrations. He has finished two more settings. The first setting is 1.1 GeV, 2.5T, transverse, with the "worst"

septum setting. He included a plot of the simulation result showing the effect of the target field. An event by event simulation was used to determine

the effective theta and phi angles. There is still a small offset in the phi angle for the central hole; this will have to be considered carefully. The

uncertainty of the dp calibration is of the same order (10^-4) as previous calibration results that have been shown for other energy settings. He has

also completed the calibration for the 2.2 GeV, 2.5T, transverse setting, this time with the "best" septum setting. Similar results were seen for this setting,

though the uncertainty in dp is slightly smaller, as the bending effect is not as large for this setting at it is for the 1.1 GeV setting. Of the 8 total optics

configurations, 5 have been completed and 1 is in progress. The last two settings should be completed in the next couple of weeks, and then it will take

~2 weeks to complete the calibrations for the RHRS. More details can be seen in his slides here.

- Gave an update on status of optics calibrations. He has finished two more settings. The first setting is 1.1 GeV, 2.5T, transverse, with the "worst"

- Jie:
- Gave an update on including radiative corrections in the simulation package. Last time, there was a question about why the un-radiated distribution (from

a carbon target) was not symmetric. It appears the value for theta used at the event generator to calculate dp is a uniform distribution, which causes the

strange shape in the distribution. He described two possible methods to get the final distribution; they are similar but the first method is weighted by the

elastic Born cross section while the second method is weighted by the radiative cross section. Comparing the two methods, the distributions for dE at the sieve

show a considerable difference. However, if you compare the distributions for the two methods at the event generator, they are almost the same. It's possible

that the second method accounts for the energy loss dues to ionization and Bremsstrahlung twice. More details can be seen in Jie's slides here.

- Gave an update on including radiative corrections in the simulation package. Last time, there was a question about why the un-radiated distribution (from

## 3/12/2014

Present: JP, Jixie, Kalyan, Jie, Min, Chao

By Phone: Melissa, Pengjia

**Feature Presentations:**

- Pengjia:
- Gave an update about the status of BPM calibrations. He is studying the BPM pedestal value for the run 3600~3900. The typical fluctuation of the

pedestal value is about 1000 channels. However, Pengjia pointed out that the pedestal value of BPM B changed during some runs (like 3714 and 3732),

especially for the channel 7 of BPM B. JP suggests that multiple pedestal values can be used in the same run to correct those big jump of pedestal values

and treat the rest small fluctuations as uncertainty. More details can be seen in his slides here.

- Gave an update about the status of BPM calibrations. He is studying the BPM pedestal value for the run 3600~3900. The typical fluctuation of the

**General Discussion:**

- Jie is working on radiative corrections in the simulation.

- Chao is working on optics calibration of 1.1GeV and will compare the result with longitudinal optics.

## 3/5/2014

Present: JP, Kalyan, Vince, Jie, Min, Chao, Jixie, Melissa

By Phone: Pengjia

**Feature Presentations:**

- Jie:
- Gave an update on including radiative corrections in simulation. Included a list of definitions for all the terminology and different processes used

in the calculations. He showed a comparison of using the peak approximation versus the exact calculation for the NH3 target using two different

radiation lengths. For small values of nu, there isn't a large difference between the methods. He also showed a comparison of using the exact

calculation method for two different radiation lengths (0.1/0.03), both with and without the multi-photon correction. Without the correction, the ratio

is pretty flat, but including the correction causes the ratio to drop for smaller values of nu. He included a plot of the total radiative corrections for the

carbon target (internal and external), and a plot showing the the carbon cross section with and without corrections. It's unclear why the uncorrected

cross section is not symmetric; it appears to already have some energy loss. Jie will check this and will also include detector resolution and acceptance,

which aren't included in these plots. More details can be seen in his slides here.

- Gave an update on including radiative corrections in simulation. Included a list of definitions for all the terminology and different processes used

- Chao:
- Gave an update on longitudinal optics. He took a closer look at the BPM x fluctuation during the course of a run; it seems the beam position is

slowly fluctuating over the course of the run. He described the method for matrix calibration; the matrix elements are calibrated by the open angle of

2 different sieve holes with respect to the scattering point. The fluctuation in the beam position will slightly influence the calibration. The matrix

calibration can be calculated using geometry relations, so he simulated several different beam positions and calculated the open angle; the results

showed that the change in angle due to the beam position is small. JP suggested that he should look at the absolute value of the sieve holes, instead

of the difference between them. He also showed a comparison of the first order matrix for the cases with and without the target field. The theta offset is

large, which is due to the bend from the target field. JP asked about the effect on the left septum after the right septum broke; according to simulation

there is ~10% effect. More details can be seen in his slides here.

- Gave an update on longitudinal optics. He took a closer look at the BPM x fluctuation during the course of a run; it seems the beam position is

**General Discussion:**

- Pengjia is working on checking the pedestals for all periods for BPM calibrations. The change in pedestals seems to be random. There also seems

to be an effect where changes in current affect the BPMS. Pengjia says this effect seems to be random, but he will show more details on this next time.

## 2/26/2014

Present: JP, Jixie, Jie, Min, Chao, Kalyan, Melissa

By Phone: Karl, Ellie, Toby, Ryan, Pengjia, Moshe

**Feature Presentations:**

- Melissa:
- Gave a short update on the inconsistency in the yields. There seems to be a correlation between beam position and yield; for p0 = 2.072 GeV/c

(2.5GeV beam, 2.5T magnetic field) setting, an ~8% drop in yields can be seen when the beam position changes ~3mm in X and ~2mm in Y. She

also tested the effect of applying different raster cuts, in case the shift in beam caused scraping. The raster cuts did not help to make the yields

agree. JP suggested that, due to our small scattering angle, a change in beam position can have a significant change in the kinematics. She will

look more into this, and look at the corresponding effect on the RHRS. Her slides can be seen here.

- Gave a short update on the inconsistency in the yields. There seems to be a correlation between beam position and yield; for p0 = 2.072 GeV/c

- Min:
- Gave an update on the pointing uncertainty. Previously, she used the carbon ground state and first excited state to determine the uncertainty.

A landau-gaussian convolution fit was used to fit the two peaks and determine the uncertainty. JP cautioned against using fits in Root, as they

can be unreliable. Min will take a closer look at this and the determination of the uncertainty. Using this method gives a d-theta of ~0.2mr, which

is within the requirement. She also showed another method to calculate the uncertainty, using the difference in energy between two nuclei (carbon

and helium), this time using a Monte Carlo simulation to determine the beam offset. The beam position at the target looks identical for both carbon

and helium, though JP suggested only using one "blob" (the "blobs" arise from drift in the beam position during the run) in order to get better

resolution. If only survey results are used, the value for d-theta is ~0.7mr. More details can be seen in Min's slides here.

- Gave an update on the pointing uncertainty. Previously, she used the carbon ground state and first excited state to determine the uncertainty.

- Pengjia:
- Gave an overview of status of BPM calibrations. The beampackage tools have been updated, he has dumped all the raw BPM data from volatile

rootfiles to a data pool and have saved all calculated positions to disk. Students can now insert this information into their own rootfiles. He is

calculating the uncertainty for each run and checking for any weird changes in beam position. His results will be published on the ELOG when he

is done. A database containing the average position for each run is built along with a script to access the information. He showed global plots

of the beam position for every run at BPMA, BPMB and the target. He also showed a global plot of pedestal values for the entire run period. Some

pedestal runs were taken with out any current (real pedestal runs), while some were taken during long beam trips. Currently, he uses the pedestal

closest in time to each production run as the pedestal value, but JP suggested breaking them up by setting instead. Pengjia is still working on how to

estimate the uncertainty for the pedestal value. More details can be seen in his slides here.

- Gave an overview of status of BPM calibrations. The beampackage tools have been updated, he has dumped all the raw BPM data from volatile

**General Discussion:**

- Moshe has his simulation ready, but needs optics calibrations! JP suggested using straight thru optics results for now.

## 2/19/2014

Present: Jixie, Kalyan, JP, Min, Chao, Jie, Melissa

By Phone: Toby, Ryan, Ellie, Karl, Pengjia

**Feature Presentations:**

- Jie:
- Gave an update on his work to determine the packing fraction using simulation. He is working on updating his simulation to include radiative

corrections. He is including a correction for the straggling effect, which arises due to "real" bremsstrahlung and ionization. He showed a comparison

between the peak-approximation method and the exact calculation, for a carbon foil. They agree within 1%, but the difference would probably be

larger for a (thicker) ammonia target. He also showed the simulated result for the radiative tail in the carbon target, which suggests that the "internal"

contribution is larger than the "external contribution, except at small values of nu. Finally, he showed the effect of the multi-photon radiation correction,

which is fairly large at small values of nu. He is still working on optimizing the code. More details can be seen in his slides here.

- Gave an update on his work to determine the packing fraction using simulation. He is working on updating his simulation to include radiative

- Ryan:
- Gave an update on the work he's been doing on the radiative corrections for small angle GDH data. At our kinematics (2.1GeV, 6deg), the cross section

has a strong dependence on the scattering angle, which means the cross section could vary greatly over the entire angular acceptance. The code used to

produce the elastic radiative tail uses one central scattering angle, so angular acceptance needs to be corrected for. He broke up the acceptance into a grid

in theta and phi bins, calculated the elastic tail at different angles across the acceptance, and averaged the results. The difference in the cross section using

the central scattering angle vs. using the average of the reconstructed scattering angles is about 20-25%. He will do a comparison of carbon/nitrogen data

for 3.7 GeV once he gets the nitrogen data from Vince. He is also writing up a technote documenting this work. More details can be found in his slides here.

- Gave an update on the work he's been doing on the radiative corrections for small angle GDH data. At our kinematics (2.1GeV, 6deg), the cross section

- Chao:
- Gave an update on the status of optics calibration. A program (g2prec) is written to read in L.gold.* (effective angles) and Lrb.tgt_0_* (bpm) type

variables as input for projection and drifting functions in the simulation package to calculate the final reconstructed variables. It will be configured by the

database to deal with different kinematic settings, and will write L.rec.* type variables into the final rootfiles as the final reconstructed scattering angle and

and momentum. He also showed a diagram depicting the structure of the "do_replay" script, which will be automated to insert all necessary information

into the final rootfiles. He is currently working on determining the calibration matrix for the 9 different optics settings, which can probably be completed in

~1 month, though the uncertainties will take longer. His slides can be found here.

- Gave an update on the status of optics calibration. A program (g2prec) is written to read in L.gold.* (effective angles) and Lrb.tgt_0_* (bpm) type

## 2/12/2014

Present: Chao, Jixie, Jie, JP, Min, Melissa

By Phone: Toby, Ryan, Ellie, Karl, Pengjia

**Feature Presentations:**

- Melissa:
- Showed a summary of checks she's done to try to understand the discrepancy in yields for packing fraction runs. Many different tests were

done testing the cuts (acceptance, PID and raster) as well as checking the multitrack efficiency and comparing the first and second half of each run.

JP pointed out a few odd things that should be resolved (such as the "spikes" in the reconstructed phi variable, events above the good electrons in

leadglass 2D plot, etc.) The difference in yields is still not clear, but it's possible that a Moller measurement that was taken between runs 3503 and

3574 could have altered the beam conditions. She will discuss with Pengjia to see if the Moller measurement had a large effect on beam position.

More details can be seen in her slides here.

- Showed a summary of checks she's done to try to understand the discrepancy in yields for packing fraction runs. Many different tests were

- Min:
- Showed an update on her pointing study to determine the central scattering angle. She showed the details of calculating the uncertainty in the

scattering angle using survey results. She used the assumption that z and x are the same for both theta1 and theta2, which JP warned could in be

incorrect. Looking at the results for the left and right HRS, the results from pointing and survey agree for the LHRS, but not for the RHRS. The pointing

uncertainty is different for left and right HRS; this is determined using the difference in the carbon ground state and first excited state, compared to

the nominal value. Min is currently writing up the details of the pointing study so far. More details can be seen in her slides here.

- Showed an update on her pointing study to determine the central scattering angle. She showed the details of calculating the uncertainty in the

- Pengjia:
- Gave an update on the status of BPM calibrations. He is working on the calibration for the optics run near 3185, but unfortunately there are no straight

through calibrations with div=2. The closest calibration is from 3/6 with div=3. Looking at the results for run 3185 using this calibration gives a beam

position of -0.84mm(X) and 2.39mm(Y) at the target. Chao's fitting result for this run was -3.5mm(X). JP asked how much a change in beam position of

3mm would affect the central angle calibration. Pengjia will try to get the calibration as good as possible, then summarize his work and determine the

uncertainty for the beam position. Also, he will compile a table of all beam condition changed throughout the run. His slides can be seen here.

- Gave an update on the status of BPM calibrations. He is working on the calibration for the optics run near 3185, but unfortunately there are no straight

## 2/05/2014

Present: Kalyan, JP, Chao, Jie, Min, Jixie, Melissa

By Phone: Toby, Ryan, Ellie

**Feature Presentations:**

- Toby:
- Working on dilution analysis. Gave an explanation of his method to determine the background yield in terms of the dilution runs (carbon,

empty, dummy). He also needed to create a scaling factor to relate the carbon runs to the nitrogen background. Using Moshe's nitrogen

simulation he was able to scale the carbon production data (with the "empty" run yield subtracted out) to match the nitrogen yield. He made

a graphical cut on the carbon and empty dilution to isolate the elastic/quasi-elastic channels so that each channel could be scaled separately.

He can then use these scaling factors to determine the overall background yield. The current scaling factors result in a background contribution

that is much too large; the yield is greater than the yield for a production run. This is most likely due to the fact that Toby currently doesn't

include any radiative corrections, which he will include in his method for next time. The details of his method can be seen in his slides here.

- Working on dilution analysis. Gave an explanation of his method to determine the background yield in terms of the dilution runs (carbon,

- Chao:
- Gave an update on the status of optics calibrations. He is currently working on longitudinal optics for the 2.2 GeV, 5T setting, since Min will

need this for her pointing study. He first used a simulation to show the effect of the longitudinal field, setting the beam position to the average

value of the BPM readout. The beam positions actually vary slightly between different optics runs, so he had to approximate the beam position for

"bunches" of 5000 events. An event by event simulation was used to calculate the effective theta and phi angle. The calibration looks pretty good

for this setting. The calibration tool kit, which combines the optimizer and the simulation, is almost finalized. He is currently working on updating

the reconstruction script to calculate the kinematic variables. More details can be seen in Chao's slides here.

- Gave an update on the status of optics calibrations. He is currently working on longitudinal optics for the 2.2 GeV, 5T setting, since Min will

- Jie:
- Working on updating the simulation package to include radiative corrections. There are two pieces to the correction; the radiation effect and the

straggling effect. The radiation effect includes the contribution from the dynamical effect (Bremstrahlung), which Jie has approximated as two

external radiator lengths. Ryan suggested just doing the full internal calculation, as it doesn't require much extra computing power. Since our target

thickness is ~0.03, the straggling effect is significant. He showed the simulated yields for the elastic nitrogen peak with and without the radiative

corrections, but neglected to include the radiative tail, which he will include this for next time. He also looked at the simulated yields using the actual

beam positions for the packing fraction runs 3503, 3574 and 3864. The yields agree within 4.5%, meaning that the differences in beam position is not

what is causing the discrepancy in the yields of the packing fraction runs. Jie's slides can be seen here.

- Working on updating the simulation package to include radiative corrections. There are two pieces to the correction; the radiation effect and the

## 1/24/2014

Present: Kalyan, JP, Chao, Jie, Min, Melissa

By Phone: Toby, Ryan, Karl, Pengjia

**Feature Presentations:**

- Melissa:
- Gave an update on packing fraction analysis. Compared the x/y beam positions for the four packing fraction runs for material 7; one

run (3727) has unreliable beam position information, but the other 3 runs seem fairly consistent. There is still a large discrepancy in the

yield for one run (3503). This is the earliest run taken; she will go through the logbook to look for any condition changes that could cause

this discrepancy. The results for the packing fraction for the other 3 runs seem fairly consistent, but lower than expected. More details can

be seen here.

- Gave an update on packing fraction analysis. Compared the x/y beam positions for the four packing fraction runs for material 7; one

- Pengjia:
- Gave an overview of his calibration method; the raw signal received in the antenna is compared to the recorded ADC value, and the

linear region is fit. This can then be rewritten using a diff/sum value and the nonlinearity corrected for. The position is then calibrated

using data from harp scans. Some of the calibrations were used for runs with different currents, assuming that the beam position

didn't change for these runs, which JP suggested was a dangerous assumption to make. There were several periods where the pedestal

was different between the calibration and production runs. This fluctuating pedestal could change the resulting beam position by ~2mm.

For next time, Pengjia will summarize the assumptions made for these calibrations so the uncertainty can be assessed for each one. More

details of his calibration method can be seen in his slides here.

- Gave an overview of his calibration method; the raw signal received in the antenna is compared to the recorded ADC value, and the

- Min:
- Gave an update on the pointing study to determine the central scattering angle. She showed the equation for elastic scattering

(which includes energy loss); she will look at the difference in the scattered energy for two different nuclei. She included two different

methods for calculating the pointing uncertainty. The first method uses the carbon-12 ground state and first excited state, and gave

a result for d-theta/theta <1%. JP suggested Min will probably need to combine left and right data to get the precision we need. The

second method combines various uncertainties (from survey, beam_x, etc.) and uses 2 different scattering angles; one including the

z-offset and one without. Using just one scattering angle to compute d-theta gives an uncertainty of ~2mr, using the quotient of the

two scattering angles gives an uncertainty of ~0.2mr, and using the difference of the two angles gives an uncertainty of ~0.04mr. She

still needs to include input for the incoming beam angle, and include the uncertainty from energy loss. More details can be seen in her

slides here.

- Gave an update on the pointing study to determine the central scattering angle. She showed the equation for elastic scattering

**General Discussion:**

- Ryan:
- Working through Rosetail to understand radiative correction calculations/code.

- Toby:
- Looking at scaling carbon data to nitrogen for dilution analysis.

- Chao:
- Working on longitudinal optics calibration.

## 1/15/2014

Present: Kalyan, Chao, Jie, Min, JP, Jixie, Melissa

By Phone: Ellie, Toby, Ryan, Karl, Alexandre, Pengjia

**Feature Presentations:**

- Jie:
- Gave an update on using the simulation package to determine the packing fraction. He showed multiple methods for extracting

the packing fraction, which account for different contributions to the overall yield. He used the g2psim package to get relative cross

sections for each contributing material. Next he will work on including the radiative corrections to the elastic peak and include the

calibrated beam position information (once it is ready). Details for the methods used can be seen is his slides here.

- Gave an update on using the simulation package to determine the packing fraction. He showed multiple methods for extracting

## 1/8/2014

Present: Kalyan, Chao, Jie, Min, Melissa

By Phone: Ellie, Toby, Ryan, Karl, Alexandre, Pengjia

**Feature Presentations:**

- Melissa:
- Gave a short update on yields for packing fraction runs. For one run (3864), the ungated livetime is significantly different then

the helicity-gated livetime. Using the average of the helicity gated LT values for the normalization makes this run agree better with

other packing fraction runs (3574 and 3727). She will check the beam position for these runs to see if this could have a large effect

on the yields. Her slides can be seen here.

- Gave a short update on yields for packing fraction runs. For one run (3864), the ungated livetime is significantly different then

- Chao
- Gave an update on the simulation package. Previously, the real theta and phi were not determined event by event, but for an entire

run. Since we know the position of the reaction point and the sieve hole, and the momentum of the electron, it is possible to use a

bisection method to determine the real theta and phi for each event. With this update it will be easier to determine the calibration for

different dp settings. Next he will work on finishing the optics calibration for the first setting with the target field. His slides can be

seen here.

- Gave an update on the simulation package. Previously, the real theta and phi were not determined event by event, but for an entire

- Min
- Gave an update on pointing analysis. The calculation was done using the March 14th calibration, using a carbon foil in liquid helium.

Using the carbon-12 ground state and first excited state to do the calibration of d(delta-E'), the results for the LHRS (4.40MeV) and

RHRS (4.42 MeV) agreed within the uncertainty with the nominal value (4.44MeV). However, including other uncertainties (survey and

beam x), add up to ~0.11 deg uncertainty in the scattering angle. She concluded that using the carbon foil in LHe is not ideal for a

pointing study. Next she will try CH2 run in longitudinal target field setting, once the optics calibration is complete for this setting. Her

slides can be seen here.

- Gave an update on pointing analysis. The calculation was done using the March 14th calibration, using a carbon foil in liquid helium.

- Pengjia
- Gave an update on the status of the BPM calibrations. He has finalized the calibrations for data taken from April 11th to May 18th,

which includes three different BPM gain settings. For settings before April 11th, the process is more complicated (larger pedestals,

auto-gain), but he will try to finalize the calibrations soon. He will provide a technote of his procedures and results. More details can

be seen here.

- Gave an update on the status of the BPM calibrations. He has finalized the calibrations for data taken from April 11th to May 18th,

**General Discussion:**

- If any students are interested in giving a talk at the APS April Meeting, please circulate an abstract to the group. The deadline for abstract submission is this Friday, January 10th.