G2p Analysis Minutes

Minutes of the weekly analysis meetings

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Agenda

7/17/2013

Present: Vince, Chao, Min, Jixie, Kalyan
By Phone: Ellie, Alex, Toby, Moshe, Pengjia, Karl

Feature presentations:

• Pengjia:
  • Present the pedestal as a function of time for the whole data sets. The pedestal were
    drifting along time, they are not stable at all. Currently Pengjia subtract only the averaged pedestal
    of a period of time to reconstruct beam position. He will need to do the subtraction run by run.
    
  • Also presented are the BPM calibration against Harp for 100, 75 and 50 nA. It seems that the
    calibration for 50 nA need to be redone. He also shown that the calibration constant is sensertive to
    beam current, whenever the beam tripped and then the beam position is not stable during the current was
    rampping up.
  • See detail here.

• Moshe:
  • Working on an event generator for simulation. Right now he is working on the energy loss caculation.
    He mentioned that the energy loss result from EStar does not agree with that from Geant4.
    
  • He is also trying to get cross section models for helium-4 and nigogen-14. He has QFS model
    in hand but this model is known to be poor. Vince agreed to provided him some N-14
    data and Moshe will try to compare P.Bosted's model with Vince's data.
  • See his presentation here.

7/10/2013

Present: Vince, Chao, Min, Jixie, Melissa
By Phone: Ellie, Ryan, Toby, Moshe, Pengjia, Karl

Feature presentations:

• Chao
  • Gave an update and summary of the helicity decoder There were a couple of bugs that needed to be fixed,
    including the one bit delay. Also, the ring buffer creates a set of unused, extra events at the beginning of each
    run, which will now be marked as an error. Finally, there was an alignment issue when inserting helicity information
    back into the rootfile. These issues should all be fixed now. When using the decoder, the variable that should be
    used to obtain the correct helicity of an event is "hel_act", and all events with hel_error /= 0 should be cut out.
  • Also working on improving the decoder to deal with beam trip cuts. The cut should be made in units of helicity
    patterns, so time information (from the fast clock) will be added to help make these cuts. His slides can be found here.

• Melissa
  • Gave a summary of her method to determine raw asymmetries including the applied cuts and method for extracting
    the asymmetry. However, the issue with the helicity decoder described in Chao's talk means that the results shown are
    not reliable. Concern was expressed over the error bars shown, she will carefully check this when she re-does the
    analysis with the correct helicity information. Her slides can be seen here.

• Min
  • Updated the LHRS optics calibration by including beam trip cuts and using the latest bpm information from Pengjia.
    The results seem better! Cuts still need to be applied for when the beam moves. Since BPMB is not always stable, she
    thought about just using BPMA to calculate the beam position at the target. Vince suggested that by correcting for the
    beam movement the poor resolution in BPM B might be less significant and Min could still get reasonable results. Her
    slides can be found here.

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7/3/2013

Present: Kalyan, Chao, Min, Melissa
By Phone: Ellie, Ryan, Toby, Pengjia, Alex

Feature presentations:

• Ryan
  • Updated the MySQL database to include Jie's results from multi-track analysis and Toby's results from target
    polarization analysis. This information is also now included in the ROOT library. Also fixed several bugs that caused
    missing information for some runs in the database. He is also working on helicity dependent deadtime analysis.
    His slides can be seen here.

• Pengjia
  • Gave an update on BPM analysis. He compared two techniques to reduce noise in the pedestal; applying a filter
    and taking the average of every two seconds of data. The two methods seem to give similar results. For next time
    he will look at how the change in current affects the position, and how using a 2Hz filter affects the mean value of
    the BPM. His slides can be seen here.

• Toby
  • Finished writing a technote for the target polarization analysis and will be looking for feedback soon. He will also
    start preparing for a second round of farm replay, since no event-type information exists in the rootfiles currently.

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6/25/2013

Present: Karl, JP, Chao, Kalyan, Min, Melissa
By-Phone: Ryan, Toby, Ellie, Pengjia, Alex, Moshe

General Discussion:

• Ryan will submit an abstract for a general g2p talk for the DNP meeting this fall.

Feature presentations:

• Chao
  • Gave an update on optics simulation package. He showed the results of comparing the reconstructed and thrown
    variables from simulation to see if he could reproduce the central value of delta, theta and phi. He determines the
    average for each variable by taking the average of each point and weighting by the cross section. Currently, his
    reconstruction stops at the target plane with z=0, which assumes that the target is symmetric along the z-direction.
    He needs to find a careful way to correct for this. His presentation can be found here

• Min
  • Gave an update of LHRS optics calibration. She worked with Pengjia to get the bpm package with filter working
    for ifarm replay (only LHRS for now, RHRS will be working soon). She used the updated bpm information to update
    her results for straight-thru optics. She found that the results for theta were larger by a factor of ~3. She will try to
    figure out if this is a result of the bpm filter or something else. She will also update her results to include cuts for
    beam trips and beam moves. Her presentation can be found here

• Melissa
  • Gave a followup on beam charge asymmetries. She updated her results to include beam trip cuts to compare with
    Pengjia's results. The effect of adding the beam trip cuts is small (~ >0.05%), and Pengjia and Melissa's results agree
    within ~1% or less. She also showed a comparison between results taken from ring buffer data and happex data.
    There is a >1% difference between the two systems. Her slides can be seen here

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6/19/2013

Present: Karl, JP, Vince, Jixie, Ellie, Kalyan, Chao, Jie, Min, Melissa
By-Phone: Ryan, Toby, Pengjia, Alex

Feature presentations:

• Ryan
  • Gave a recap of the y-target calibration for the LHRS. Last time he showed that he got strange results
    during the optimization, specifically for the (0,0) and (-4,0) settings. By using a different run for
    the (-4,0) setting he was able to improve the results. He then tried maximizing the event number per hole,
    while still keeping the number of events approximately the same per hole. This improved the resolution of
    the results. He also tried increasing the order of the optimization in the database. This also improved
    the resolution, but may not be a reasonable solution since increasing the order can over constrain the matrix.
    His presentation can be found here.

• Pengjia
  • Gave an update on BPM analysis. He is currently rewriting the insert and calibration piece of the
    beampackage to include the new filter method presented last time.
  • Also working on a beam move check that uses rms detection for fast beam moves, looks at current trip
    information, and splits events if the beam moves more than 0.3mm. He is still debugging this. He
    also discussed pedestal subtraction for the bpm calibration. The pedestal shown was quite wide and had
    multiple peaks. Pengjia will study this more to determine if this behavior is consistent through all runs,
    or if this was a specific period when conditions were changing. His presentation can be found here.

• Toby
  • Worked with Josh and James to determine that there was in fact a bug in the online code to determine
    target polarizations. This means the 2.5T polarization is actually ~50% of what was reported online.
    This does not affect the 5T results.
  • Showed details for his method of determining the TE points. He takes the time reported online for the
    TE as the approximate start time, does a 0th order fit of the points and looks at the chi-squared value.
    He then adds points until he finds the end point of the TE. Finally, he adds points at the beginning of
    the TE to minimize the chi-squared value. The polarization is then averaged over each run. He questioned
    how the polarization decay contributes to the uncertainty for each run, since the poarization is actually
    decaying over each run. JP suggested using the average of the decay curve to determine this. Toby's
    presentation can be found here.

• Jie
  • Has completed the efficiency study for multi-track events. This information will be in the mysql
    database soon.
  • Also working on data quality checks for optics variables. He looked at the t0 calibration first. One
    concern is how "negative time" events are being dealt with. Jie will check that they aren't being cut out.
    He also looked at the transport and rotated x,y,theta and phi variables. Within each kinematic settings,
    these varibales look stable over all production runs. Jie will take a closer look the elastic settings next.
    His presentation can be found here.

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6/12/2013

Present: Karl, JP, Vince, Jixie, Chao, Jie, Min, Alexandre, Kalyan, Melissa
By-Phone: Ellie, Toby, Ryan, Moshe, Pengjia

Feature presentations:

• Chao
  • Has fixed the bit-shift problem in the offline helicity decoder. The next round of farm replay will
    have correct helicity information.

• Melissa
  • Showed a comparison between her and Pengjia's results for beam charge asymmetries. The results
    show ~0.5% difference. It's possible that the beam trip cuts that Pengjia used is the reason for this
    difference. Her presentation can be found here.

• Min
  • Showed an update of angle and vertex matrix calibration results using previous bpm calibrations. The results
    are not better. She is still working on improving it by applying beam current cuts and beam position cuts.
    She will also try using a different run to optimize that has the same conditions but a more stable current
    She will check that the beam position is also stable during this run. Her slides can be found here

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6/5/2013

Present: Karl, Vince, Kalyan, Chao, Jie, Min, Melissa
By-Phone: Ellie, Toby, Ryan, Moshe, Guy, Pengjia

General discussion:

• There will be a practice talk for Min's Hall A Collaboration Meeting talk sometime soon (Friday or Monday?)

Feature presentations:

• Moshe
  • Gave an update on the status of GEp analysis. He did a first round of analysis without calibrations,
    to determine a general procedure for analysis. He showed preliminary results for elastic peak
    identification, binning optimization, dilution factors and asymmetry extraction. He is also working
    on writing a GEp event generator for HRSMC. His presentation can be found here.
  • Details of status of GEp analysis can be found in this document, written by Moshe.

• Pengjia
  • Working on improving BPM resolution. He added a low pass, software FIR filter when processing
    the data, which seems to work very well. The previous results were 7-8X larger then the results that
    have been processed with the filter. He is working on incorporating this into his beampackage code,
    and will repeat his BPM noise study using the filter. Will also check if the central value changes at all
    as a result of the filter. His presentation can be found here.

• Ryan
  • Working on the LHRS Y-target calibration. He optimized 3 runs in the 2.2 GeV (0T, 6deg) setting
    with different beam positions; (4,0), (0,0), (-4,0). The results seemed strange, specifically for the (0,0)
    and (-4,0) settings. He first tried optimizing each run individually, which gives results that make sense.
    He then tried optimizing them in pairs, and got reasonable results except for the combination of (0,0)
    and (-4,0). Finally, he tried to check these results using other runs with the same beam positions, but
    found that during these optics runs, the beam position was never moved back to (0,0). Vince pointed
    out that the typical resolution for y-target is ~1mm, so these results may be ok. Ryan's presentation
    can be found here.

• Toby
  • Showed updated target polarization calibration constants. He decided to use a 3rd order polynomial
    to fit the wings of the baseline-subtracted signal. It's possible that the discrepancy between using a
    2nd and 3rd order polynomial could result from the signal "bleeding" into the wings. He described his
    method for minimizing the reduced chi-squared to find the TE points. He starts with a set of 15 points
    where the target is most thermalized, and adds points from the beginning/end of the TE to further reduce
    the chi-squared.
  • He also found that the 2.5T calibration constants found offline are ~50% smaller than what was determined
    online. He will work closely with James/Josh to confirm that this really is a problem. His presentation can
    be found here.

• Jie
  • Showed an updated version of multi-track efficiency analysis. He determined that his new method of
    including background cuts is not as reliable as his previous method to determine uncertainty. By including
    background cuts, the systematic uncertainty is decreased by about 20%, but it very position dependent, so
    he suggests staying with his previous results. His presentation can be found here.

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Jan-May 2013

Minutes_Jan2013_to_May2013

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April-Dec 2012

Minutes_Apr2012_to_Dec2012

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Jan-March 2012

Minutes_Jan2012_to_Mar2012

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July-Dec 2011

Minutes_July2011_to_Dec_2011

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Jan-June 2012

Minutes_Jan2011_to_June_2011

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