[clas12_rgk] trigger efficiency vs ECal treshold

[Francois-Xavier Girod]

Dear Viktor

I have those series of over-informative plots as attached in case they can
help the discussion
They show the kinematic coverage for a given beam energy

Units are GeV and degrees. For instance, the points
( Q^2 = 2 , W = 3 ) corresponds to approximately ( mom = 1.1 , theta = 30 )
( Q^2 = 5 , W = 2.5 ) corresponds to approximately ( mom = 1 , theta = 53 )
(this point is off scale on the plots)
The 35 degree angle at W = 2.5 occurs around Q^2 = 3.8 and mom = 1.6

Best regards
FX

On Wed, Dec 12, 2018 at 6:26 PM Viktor Mokeev <mokeev at jlab.org> wrote:

> 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> 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> on behalf of
> Francois-Xavier Girod <fxgirod at jlab.org>
> *Sent:* Wednesday, December 12, 2018 5:58:01 PM
> *To:* clas12 rgk; 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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