[Clas12_first_exp] New, more complete studies of spring and fall luminosity scan runs

[Mac Mestayer]

Hello all;

I suggest that we be more conservative and not go to higher luminosity.

The figure of merit that is being used is simply the total number of
reconstructed events per beam time.  So it is the smallest statistical
error per beam time.

However, I would like to point out 2 things:

1) many experiments will be dominated by systematic errors and
not statistical errors, and the systematic error attributable to
luminosity-dependent tracking efficiency is proportional to the
size of the inefficiency; and it gets larger with higher luminosity, and

2) it is likely that there will be many studies which take advantage
of CLAS's ability to do exclusive physics and which will involve more
than 3 charged tracks, so

I don't think it is smart to run with inefficiencies higher than
about 10% or 20% except in special cases.

                                    regards, Mac

                         

----- Original Message -----
From: "Stepan Stepanyan" <stepanya at jlab.org>
To: "clas12 first exp" <clas12_first_exp at jlab.org>
Sent: Sunday, October 28, 2018 3:02:54 PM
Subject: [Clas12_first_exp] New,	more complete studies of spring and fall luminosity scan runs

Dear all,

I just posted a presentation with studies of forward detector charged particle reconstruction efficiency as a function of beam current. I used both spring and fall luminosity scan runs, processed with latex CoatJava (or almost latest). Results are not so different than what we had from August studies. We should dig deeper to understand where the looses come at high currents and see if we can mitigate these losses with. I see few options to explore. In the mean time, I propose to increase beam current for production runs for the remaining of the RG-A run to max allowed value defined by safe operations of detectors. From what I can see from DC currents, we may be able to go to 55 nA.

Regards, Stepan
 
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