PMT%20time%20offset%20calibration%20(not%20completed)

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PMT time offset calibration(not completed)

• R.Sawada
• 27/Dec/2007

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• Database to store time offset of each PMTs were
  prepared. This is similar to gain and Q.E.
  database.
• A task to compute time offset by using LED runs
  was prepared (XECPMTTimeOffsetCompute). This is
  available with xec affiliation.
• Time offset calibration during analysis was added
  to XECPMTFill task. This is used when DRS time is
  used for analysis.
• Time offset simulation was added to bartender.
  Time offset during simulation and analysis can be
  different.

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Procedure 1 (Estimation of time)
Estimate time
Correct run offset
At the end of these steps, following data is
obtained. A point corresponds to a PMT in a run.
Time offset nsec
Distance cm
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Procedure 2 (Minimization)
Parameters Speed of light, time offset of each
PMTs.
Minimization is done by Minuit. Parameter for
Minuit is only the speed of light. Minimization
of time offset of PMTs is done in fitting
function.
At the end of these steps, following data is
obtained. A point corresponds to a PMT in a run.
Time offset nsec
Distance cm
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Result ?

• It seems there is still a problem to align time
  of different runs. The final result will be after
  the problem is solved.
• With current implementation, speed of light is
  faster than c. This might be solved by improving
  alignment of runs.

Time offsets are shifted so that mean of all PMTs
becomes zero.