[clas12_rgk] trigger efficiency vs ECal treshold

[Viktor Mokeev]

Dear All,


 From FX trigger efficiency plot, I see efficiency problems at the lab. energies of the scattered electron <2.0 GeV or for \nu value above 5.5 GeV for the electron beam energy 7.5 GeV. It corresponds to the following W ranges where we have the problem with trigger efficiency:


Q^2=2.0 GeV^2 W>3.0 GeV

Q^2=5.0 GeV^2 W>2.5 GeV


For hybrid baryon search, we have no any problem with the trigger efficiency at Q^2<2.0 GeV^2 since the lightest hybrids are expected in the mass range <2.5 GeV.  Furthermore, the initial search for hybrid baryons will be carried out at Q^2<2.0 GeV^2.


 Best Regards,

                                 Victor


________________________________
From: Francois-Xavier Girod <fxgirod at jlab.org>
Sent: Wednesday, December 12, 2018 6:09:53 PM
To: Viktor Mokeev
Cc: clas12 rgk; clas12 first exp; Rafayel Paremuzyan
Subject: Re: [clas12_rgk] trigger efficiency vs ECal treshold

Dear Viktor

Rafo can confirmed as he produced the plot, my understanding is that the electron momentum is measured by the drift chambers

Best regards
FX

On Wed, Dec 12, 2018 at 6:08 PM Viktor Mokeev <mokeev at jlab.org<mailto:mokeev at jlab.org>> wrote:

Dear FX,


 Just to make sure, whether P on your plots is the energy=momentum of the scattered electron?


Best Regards,

                                    Victor

________________________________
From: clas12_rgk <clas12_rgk-bounces at jlab.org<mailto:clas12_rgk-bounces at jlab.org>> on behalf of Francois-Xavier Girod <fxgirod at jlab.org<mailto:fxgirod at jlab.org>>
Sent: Wednesday, December 12, 2018 5:58:01 PM
To: clas12 rgk; clas12_first_exp at jlab.org<mailto:clas12_first_exp at jlab.org>
Cc: Rafayel Paremuzyan
Subject: [clas12_rgk] trigger efficiency vs ECal treshold

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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