Notes

Create a collection of compressed rechits, storing only the detid, energy and time.

• detid is a uint32_t
• Time is stored as a int16_t with a range of +/- 32.767 ns
• Energy is stored as a uint16_t with a max of 655.35 GeV

so each hit is 8 bytes. Only hits with flags = 0 will be stored in the collection. A separate producer will make the collection which we can add in a sequence in the PhiSym analysis.

We need to store every time and energy to be able to determine the stability of our calculation with different cuts.

The collection will be read in by the EcalCrystalTimingCalibration class which will perform the analysis The analysis will apply an energy threshold, calculate mean/stddev of timing, and recalculate the mean/stddev inside a 2 sigma window. This window helps avoid bias to highly out of time events.

TODO: Find out about ChiSquared for cutting on out of time pileup.

If we notice that the output root file size is too large, we store a vector of time and energy per lumisection and store the detid only once per lumi. Another idea for extremely high occupancy would be to store binned sums, allowing for a courser 2 sigma window to be made.

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