Instructions for analysis shifts

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Instructions for analysis shifts / VCS E12-15-001 experiment

• Connect to cdaql1: ssh cdaql1 and go to /home/cdaq/vcs2019/hallc_replay_vcs

Warning: from this directory, please don't make any modifications on the source code. If you want to do tests or modify things, go to github and fork to your personnal directory. The source code is available from: Before starting to run it after getting your fork, run: ""

Kinematic setting

- For each new run, the file: DBASE/COIN/standard.kinematics is updated. Check regularly if it is the case: electron momentum needs attention.

- If needed to manually enter a new run, type new values for: beam energy (in principle it won't change), target mass (amu), HMS and SHMS central momentum and angle, particle mass detected in each arm (in principle, it won't change: proton in HMS, electron in SHMS). Note that the names of arm variable start with letter "h" for HMS and "p" for SHMS.

Analysis monitoring

This step should be done by the TO. Any regular TO tasks have the highest priority over analysis replay and if target needs attention, the TO should just take care of the target and not do the analysis replays.

- After ~100,000 events run the "partial" analysis replay:

> ./run_partial_replay.csh (run number) (# events) (process = elastic, vcs...) (target = LH2 or dummy)

After the partial replay is finished, you should check the run table to make sure the singles yields in the HMS and SHMS are consistent with the previous runs. The appropriate command for this is:

> ./make_vcs_table

After the run is finished, the full replay will start automatically. Do not run the partial replay after that as it will overwrite the database entries made by the full replay.

If a more in-depth analysis needed or if you need to change a cut in analysis (see below the time delay), you can start the analysis program directly.

  • Changing a cut: edit Ana/ANA_CUTS.input (write a note if you need to change another cut than the coincidence time delay).
  • Changing histogram limits or binning: edit Ana/ANA_HIST.input
  • Please don't change any source code in this directory.

To run the analyzer only:

> ./run_ana_only.csh (run number) (# events) (process = elastic, vcs...) (target = LH2 or dummy)

The source code is in the Ana directory. Read instructions on Ana/README.txt if you would like to run directly the code.

Things to check

At the end of the job, databases will be built. Coincidence analysis information to check will be visible on the terminal. Follow the steps:

  • Database printout:

- First things to check is if the luminosity has been measured the same from HMS and SHMS.

- Then check timing information: is the delay set properly? Is the main timing peak found when fitting much larger in term of number of events than accidentals? Is the number of events in peak subtracted from the accidentals significant?

- Missing mass distribution (kinematic dependent): 3 lines correspond to possible 3 found peaks in the squared missing mass. The first line should show a peak at M(pi°)^2. If not something is wrong and write a note about it for this run, check at the monitoring plots if there is a peak. If no peak found in this missing mass squared distribution it may be a major issue such as being offset. -> CONTACT RC

For most of the kinematics: peak at 0 mass need more statistics and background studies to be visible, it might have been found by the fitter code.

  • Monitoring figures:

All the figures to look at will pop-up in a condensed replay "ana_monitor_(run).pdf. If additionnal check need to be done, open the extra pdf files as indicated. Extra monitoring: Ana/Results/cointime_(run).pdf, Ana/Results/kinematics_(run).pdf, Ana/Results/kinematics2D_(run).pdf, Ana/Results/positions_(run).pdf, Ana/Results/exclusivity_(run).pdf

1) Look at the coincidence time distribution for ROC2: if no peak is found there is a problem. If no peak is found near 0 and/or no peak for the red curve, change the time shift in ANA_CUTS.input and replay the analyzer.

2) Kinematic distributions

3) Exclusivity distributions: check missing mass fit. One or two peaks have to be found, the main one being at M(pi)^2. If not, check why and if it cannot be understood quickly call the RC.