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["Hughes, Charles [PHYSA]" <chughes2 AT IASTATE.EDU>]

Hi Christof,

Thanks this helps a lot. I think the best way forward is to bring this exact issue up at the SCM today at 330 PM - could you please call in or show up at 1008 ?

https://bnl.zoomgov.com/j/1614645041?pwd=bmE4STBRZk5tVVVUUC8zRnQxSlFyQT09

I’ll make notes in the google doc but hand over this part of the TPC update to you so you can ask this question directly to run coordination/period coordination. Today is probably the best day to do it as it’s Jamie’s last day as period coordinator and I think he’s best suited to answering the questions about triggering.

I fear the answer you’re going to get is that the triggering group is more concerned with establishing a working baseline and not yet ready to trigger on multiplicity. However, let’s ask the question as I’m not sure I’ve hear any other subsystems do so yet. Let’s see.

Thanks 

Sent from my iPhone

On Jul 3, 2023, at 10:14 AM, Christof E Roland <cer AT mit.edu> wrote:

Hi Charles, 

given we crrently have to manally assembel the events skipping through 10s or 100s of events to find one that is eductionaly valuable is prohibitive. 

At moderately low interaction rate O(100Hz) is fine.

The question is if we can assmble a trigger that selects on the Z position to be close to 0, +- 10 cm is fine.

More importantly we need to select on collisions, but reject central events. In central events the combinatorics is prohibitive to run tracking with wide open cuts. 

Cheers

   Christof 

On 3. Jul 2023, at 16:04, Hughes, Charles [PHYSA] <chughes2 AT IASTATE.EDU> wrote:

Hi Christof,

“the prospect of getting some low multiplicity data with some defined vertex positions.”

Logistically, a proposal for low rate collisions could be requested and planned for later in the week. Currently, the lowest ZDC rate we have been delivered is 100 Hz with a 2 mrad x-ing angle. I’m not entirely sure what this means for low multiplicity - but I’m also not sure we can ask C-AD to go lower.

As far as well defined vertex positions and online cuts - when we have the 2 mrad x-ing angle, it seems to me we typically see something like this in the MBD OnlMon:

(In the best case - in worst cases the T0 distribution has 2 peaks which is not 100% understood but maybe due to an MBD that’s not completely calibrated yet).

That is, the z vertex distribution is not quite centered at z = 0 (which maybe does not matter so much) but has a width of > 10 cm (which is maybe not well defined to your liking).

Indeed, in the data for the runs we have now that you are analyzing (like the low rate + field on data), we already should have something that looks like this. So I take it that the picture above is not good enough for tracking purposes ?

Not sure how we would make online cuts in the data other than just asking the data monitor to constantly watch the z vertex distribution and label those runs which have “good” and “bad” distributions so we can reject the bad later. Anything more complicated would have to be discussed with the folks who work on the trigger (CU Boulder group: Jaebeom Park + Dan Lis + Jamie Nagle & John Haggerty. Possibly MBD group as well with Mickey Chiu).

That’s all the info I can provide but from your end it would help if we got more quantitative definitions of “low multiplicity”/“good z vertex”/“online cuts”.

So, all in all what you ask may be possible - but as you say needs discussion.

Sent from my iPhone

On Jul 3, 2023, at 9:44 AM, Christof E Roland via sPHENIX-calibration-l <sphenix-calibration-l AT lists.bnl.gov> wrote:

Hi Ross, 

one thing I wanted to discuss with you and the TPC experts was the prospect of getting some low multiplicity data with some defined vertex positions. 

i am not sure if the trigger detectors are commissioned to a level that allows us to make an online selection like this, but it would be great if we could procure such a sample. 

With the current status of the "manual" offline event building making such a selection offline is near impossible. 

With the current data it looks like the clustering efficiency for MIPs is too low to reliably track particles. All reconstruced tracks I have seen so far 

are obvious secondaries and highly ionizing.

Let me know if you have a minute in the next few days to discuss this.

Cheers

   Christof

On 3. Jul 2023, at 03:48, Ross Corliss via sPHENIX-calibration-l <sphenix-calibration-l AT lists.bnl.gov> wrote:

Dear Distortions Folks,

I gather some of us will have unusual schedules given Tuesday's holiday in the US.  I propose to cancel the usual distortion meeting tomorrow (MONDAY) in favor of email updates, and task-focused discussions for those of in person in various places.  If there are pressing issues that need to be discussed live before next week, let me know.  Otherwise, please feel free to send updates via email, and post any slides you'd like to share at the usual place for posterity:

https://indico.bnl.gov/event/19847/

-Ross

==========

Dr. Ross Corliss
Research Assistant Professor
Center for Frontiers in Nuclear Science
Stony Brook University
virtual office:  https://stonybrook.zoom.us/my/rossoffice?pwd=ZmZ2SlRIMVFvUUJwbUkyOVNVTmE5QT09

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