[clas12_rgk] trigger efficiency vs ECal treshold

[Francois-Xavier Girod]

Dear all

During today's meeting I attempted to have a discussion on the trigger
efficiency as function of ECal threshold. Contradicting statements were
made during the meeting, so I want this discussion to be on record here.

Please see the plot

https://www.jlab.org/Hall-B/secure/clas12/rec_mon/P_Good_emWithEC_5786.png

from Rafo's study of the trigger efficiency. He analyzed run 5786 which was
taken with the random trigger.

- in blue all "good electrons" with Nphe>2, E_PCal > 60 MeV, sampling
fraction > 0.2 and fiducial cuts

- in orange, the electrons satisfy in addition E_ECal > 300 MeV

- in red, the events for which the orange set was missing the electron
trigger bit

The trigger efficiency is defined as (orange - red) / orange

https://www.jlab.org/Hall-B/secure/clas12/rec_mon/Eff_All_Good_em_trg_threshold_5786.png

The trigger efficiency below 2 GeV drops rapidly, and measuring a cross
section in this region is challenging

My question during the meeting was: do we already have data to show the
trigger efficiency when the threshold is 150 MeV. My understanding is that
we do not have this data and that to answer this question we need to take
another random trigger run with the lower threshold.

What I have in mind is the following: I agree that the bulk of the RG-K
data taking can take place at 300 MeV ECal trigger threshold and highest
possible luminosity, but I would like to consider the possibility to take a
few days at a lower trigger threshold to extend the cross section
measurement  to higher W. Again my purpose is to minimize the final
systematic uncertainties.

Best regards
FX
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