[Primexd] [EXTERNAL] Re: Question

[Shepherd, Matthew]

Hi all,

I would argue that you should take an approach that is driven by the need to solve problems.  I think this is what Sasha was advocating for.  As you know manpower is very limited.

Regarding this specific discussion, we attempt to use the method Ilya sketches, but as Igal points out, the energy scales and variations are larger.  Certainly by putting a fixed threshold you can simulate the cut better, but one needs to be sure the distribution of the variable being cut is also properly simulated.  We've attempted to do that, but then stopped short of putting the cut in the argument that it is bad to throw away information.

Sometimes you must throw away information to ensure reproducibility in simulation -- this is the essence of fiducial cuts.

We can debate back and forth the pros and cons of all approaches, but it is kind of an academic discussion.  If I were in your position, I would try to look for biggest problems or systematic sensitivities in the simulation.  As Sasha said, this can be done by looking at variations of extracted Compton under a variety of different choices in the analysis.  Then when a signficant effect is observed try to drill down all the way to the root cause, maybe as far as things like Ashot was suggesting to try to control/calibrate gains of PMTs based on LED system.

I think if you don't pursue a pragmatic strategy like this, there is risk of consuming significant manpower to create an alternative simulation approach that, while completely justified and may be similar to that used in other experiments, does not result in a significant reduction of systematic error.  And then you'll have to spend time fixing the real systematics limitations when they arise.

That's just my two cents -- which may not even be worth two cents!

Cheers and I enjoyed the opportunity to talk about this at length yesterday afternoon.

Matt



On May 14, 2020, at 1:05 PM, Igal Jaegle <ijaegle at jlab.org<mailto:ijaegle at jlab.org>> wrote:

Thank you Ilya, for the clarification as the threshold in FCAL is 25 times higher with a 5 MeV RMS from channel to channel, should we chose the same approach i.e. set the threshold at the lowest possible values or try to uniform it for most channels? What do you think?

tks ig.
________________________________
From: Ilya Larin <ilarin at jlab.org<mailto:ilarin at jlab.org>>
Sent: Thursday, May 14, 2020 12:56 PM
To: Igal Jaegle <ijaegle at jlab.org<mailto:ijaegle at jlab.org>>; Ashot Gasparian <agaspari at ncat.edu<mailto:agaspari at ncat.edu>>; primexd at jlab.org<mailto:primexd at jlab.org> <primexd at jlab.org<mailto:primexd at jlab.org>>; Gan, Liping <ganl at uncw.edu<mailto:ganl at uncw.edu>>
Subject: RE: Question

that was read from the table,
it was about 3-5 counts and a count was approximately 1 MeV.
Ilya

________________________________
От: Igal Jaegle <ijaegle at jlab.org<mailto:ijaegle at jlab.org>>
Отправлено: 14 мая 2020 г. 12:54
Кому: Ilya Larin <ilarin at jlab.org<mailto:ilarin at jlab.org>>; Ashot Gasparian <agaspari at ncat.edu<mailto:agaspari at ncat.edu>>; primexd at jlab.org<mailto:primexd at jlab.org> <primexd at jlab.org<mailto:primexd at jlab.org>>; Gan, Liping <ganl at uncw.edu<mailto:ganl at uncw.edu>>
Тема: Re: Question

Thank you, Ilya, What was this threshold in MeV and by how much it was varying from channel to channel?

tks ig.
________________________________
From: Ilya Larin <ilarin at jlab.org<mailto:ilarin at jlab.org>>
Sent: Thursday, May 14, 2020 12:50 PM
To: Igal Jaegle <ijaegle at jlab.org<mailto:ijaegle at jlab.org>>; Ashot Gasparian <agaspari at ncat.edu<mailto:agaspari at ncat.edu>>; primexd at jlab.org<mailto:primexd at jlab.org> <primexd at jlab.org<mailto:primexd at jlab.org>>; Gan, Liping <ganl at uncw.edu<mailto:ganl at uncw.edu>>
Subject: RE: Question

Hi Igal,
in the PrimEx simulations, we just add electronics noise first,
then cut the channel signal at our sparcification threshold:
whatever is below - set to zero.

 Ilya

________________________________
От: Igal Jaegle <ijaegle at jlab.org<mailto:ijaegle at jlab.org>>
Отправлено: 14 мая 2020 г. 12:46
Кому: Ashot Gasparian <agaspari at ncat.edu<mailto:agaspari at ncat.edu>>; primexd at jlab.org<mailto:primexd at jlab.org> <primexd at jlab.org<mailto:primexd at jlab.org>>; Ilya Larin <ilarin at jlab.org<mailto:ilarin at jlab.org>>; Gan, Liping <ganl at uncw.edu<mailto:ganl at uncw.edu>>
Тема: Question

Liping, Ilya, Ashot,

Currently, in the MC simulation, the energy threshold for a detector to be included in a cluster is calculated from the data gains ie it is varying from detector to detector and is run-dependent. To minimize the systematics should we leave the situation as it is or think of a different approach. I am thinking (naively) that it might be better to set this threshold to value at least 20 to 30% to what it is actually and possibly to set the threshold in a way that is the same for most detectors, and all runs both in data and simulation. What are your inputs in this or what did you do in previous PRIMEX measurements?

tks ig.
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