[Primexd] [EXTERNAL] Re: Accidental background subtraction

[Shepherd, Matthew]

Igal,

Thanks for sending code!

On Apr 16, 2020, at 7:44 AM, Igal Jaegle <ijaegle at jlab.org<mailto:ijaegle at jlab.org>> wrote:

Beam Photon factory is selecting the detector with the best timing or one can request it is only using the photons.

I think above you mean the EventRFBunch factory.  Are you making this request to use only photons?

This makes sense.  It seems like your algorithm may do two things then, one of which is done by the standard algorithm:

1) it verifies that the two photons from the pi0 come from the same bunch by looking at delta t
2) it verifies that both photons also come from the bunch that seems to be consistent with producing the event (...bunch as determined by looking at timing signals in all detectors)

I think the standard algorithm does 1 but not 2.  If you had very high rates, you might imagine that there are background photons that are uncorrelated with each other but are consistent with coming from the same bunch.  Therefore they satisfy criterion 1 but they may be eliminated by criterion 2 because they wouldn't have fired the trigger.

It will be interesting to see the significance of this subtraction once you purify the sample based on trigger bits.  That would help indicate whether a similar criterion might also be added to the standard calibration to improve performance.

Matt

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