[Primexd] [GlueX] Run Coordinator Report, April 3 - April 10

[Ilya Larin]

Hi Matt,
Thanks for the good question, I think we have to come up with the final answer at some point.
I tried to quickly look at the numbers and here is what I got
looking at the production angle distribution sent in the report,
and having in mind it is roughly 75% of the entire statistics,
I would say it corresponds to 5K Primakoff events total
if we will use those cuts in the analysis or about 12K events below 1 degree.
In that plot, we used cuts which are not optimized. Hopefully, further progress
in this direction will help us to relax the cuts to allow more events to pass.
Also one has to keep in mind, that energy range in the proposal was 10.5...11.7GeV
and here we have used 9.0...11.17GeV since the beam energy itself was lower.
Anyway, the photon flux rate in the region of interest in the proposal was 7.6MHz.
I think we were running at the lower rate to reduce accidentals (one can calculate how much lower,
using the 5mm collimator acceptance, 200nA beam current, and 10^-4 r.l. amorphous radiator).
I tried to estimate the overall number of triggers written on LHe target
and I got the value ~40B (if I didn't miss anything). For two hours of running with a very good beam,
we have about (1/5.5) B of recorded events, which gives 18.5 days of continuous
uninterruptable running on LHe starting from March 4th, when LHe target was installed
(the proposal number was for 40 days on LHe).
One more time: that is my quick estimation, I can make a mistake of course somewhere.

All the best,
Ilya


________________________________
От: Shepherd, Matthew <mashephe at indiana.edu>
Отправлено: 12 апреля 2019 г. 10:25
Кому: Ilya Larin
Копия: primexd at jlab.org
Тема: Re: [GlueX] Run Coordinator Report, April 3 - April 10


Hi Ilya,

How do the Primakoff yields compare with expectations from the proposal?

My understanding is that the plan was a 1% statistical uncertainty (10,000 Primakoff events) in the beam energy range E > 10.5 GeV.

Matt


> On Apr 10, 2019, at 9:39 PM, Ilya Larin <ilarin at jlab.org> wrote:
>
> Dear colleagues,
>
> The past week of PrimEx-D running was smooth and productive. We have collected almost 9B triggers on LHe target and half billion triggers on empty target (Monday 5 pm till Tuesday 1 pm). The target was emptied on Monday during beam studies and refilled Tuesday afternoon.
>
> We had 122 hours of the acceptable beam (out of scheduled 160 hours), and used 116 hours. Half of the total lost 6 hours was because of FCAL bases and HV crate replacement, which was partially overlapped with target refilling. Another half of the lost total time was due to stopping and starting runs and DAQ crashes (30 min). The beam energy fluctuations were within +/- 5 MeV.
>
> Up to now, we have collected 122% of the expected data for this spring period of PrimEx-D. Accelerator machine performance exceeded the expected 1/2 value.
>
> The attached plots show exclusive eta distribution on production angle for beam energy greater than 9 GeV collected till April 4th on LHe target. That is of course very preliminary and a lot of work is ahead. For comparison, I attached the plots from the previous Primakoff eta measurement. The bottom figure shows the Compton signal collected by that time on LHe target and scaled empty (black histogram).
>
> Ilya Larin
> Run Coordinator
>
> <rc_report_plot.pdf>_______________________________________________
> GlueX-Collaboration mailing list
> GlueX-Collaboration at jlab.org
> https://mailman.jlab.org/mailman/listinfo/gluex-collaboration

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mailman.jlab.org/pipermail/primexd/attachments/20190413/50e122e6/attachment-0002.html>