sPHENIX tracking discussion

["Perepelitsa, Dennis" <dvp AT bnl.gov>]

Dear Joe and all,

Congratulations on the paper and tremendous work that it represents!

Please find some comments below.

general: the paper uses both “upsilon” and “Upsilon” — good to standardize 

line 53: “as many as 1,000 particles” - to me this implies an upper limit. I thought measurements in PHOBOS found dN/deta ~ 600 in 0-10% collisions, which would result in ~1200 particles in our acceptance, and higher in more central events. Thus, perhaps better to write “on the order of” or “approximately"?

line 115: suggest “To separately measure” — it is really the separation between states that is the motivation for the resolution.

line 118: I’m curious about the choice of pT range here. An Upsilon at rest will produce two ~4.5 GeV tracks. However, depending on the direction of the boost compared to that of the decay electrons, you might have tracks at significantly lower or higher momenta. So why quote 4-8 GeV, instead of, e.g. 2-8 GeV? Why quote a range at all - what sets the 8 GeV? 

Fig. 2: would it be useful to add something to indicate the scale? Can one render a ruler near the z=0 point in both figures, for example?

L135, L139, L262, possibly other points: the line spills past the right margin

L167: suggest “are then schematically associated” ? (or “conceptually” ? “abstractly” ? ) — something to indicate this is a fiction being performed in software

L174: “flow chart that demonstrates the work flow” - reads funny

L180: “with” -> “on” ?

Fig. 3 caption: “serves as a wrapper to that interfraces” — some grammar issue

L198: suggest to really spell it out for a reader who isn’t familiar for how we happens to do this in sPHENIX: “which each have 100 pions” and similarly in the Fig. 4 label: “100 points / event”

L200: seems unusual to give an important definition in the caption - should be in the paper body proper.

L205 and L221: “internally to” - not sure this is the proper usage (although I am not a native speaker). “internally within”?

Figs. 4: the points visually extend down to pT = 0. is the drop in efficiency in that very first point due to particles thrown below the effective minimum pT given the sPHENIX magnet? or is it a real decrease in the seeding efficiency for tracks we should otherwise be able to measure. I think you should add something about this.

L276-281: is this something we are speculating, or have we quantified that this is responsible for a “wasted” X seconds of the 10? as it is, the statement seems a bit contextless…

L267: perhaps “The realism of the track reconstruction procedure” ? The track reconstruction itself is not being “limited” by this — in fact, it benefits.

L295: suggest “and correcting for them in the track reconstruction”. 

L301: “to determine their estimated position” reads redundantly (you could  just write “to estimate their position). Perhaps you mean something closer to “to better determine their true position” ? 

L344: add p+Au here to be consistent with the introduction

Dennis

On May 19, 2021, at 8:33 AM, Osborn, Joe via sPHENIX-tracking-l <sphenix-tracking-l AT lists.bnl.gov> wrote:

Hi All,

I got some comments from Bill (thanks to Bill for the feedback), but didn't see any others. Please take a look at the paper by the end of this week, so that we can at least have some discussion about it at the upcoming tracking meeting on Monday.

Joe Osborn

---------------------------

Joe Osborn, Ph.D.

Postdoctoral Research Associate

Oak Ridge National Laboratory

osbornjd AT ornl.gov

(859)-433-8738

---

From: W.A. Zajc <zajc AT nevis.columbia.edu>
Sent: Monday, May 17, 2021 6:43 PM
To: Osborn, Joe <osbornjd AT ornl.gov>
Cc: sphenix-tracking-l AT lists.bnl.gov <sphenix-tracking-l AT lists.bnl.gov>
Subject: [EXTERNAL] Re: [Sphenix-tracking-l] Tracking Paper Internal Release

 

Dear Joe, Tony, Jin, Hugo, Michael, Chris and Christof:

Thanks for this very interesting and informative write-up!

Below please find my comments. Most are stylistic rather than substantive, but there are some remarks at the end concerning the conclusions. 

Best regards,

Bill 

—————————————————

W.A. Zajc
I.I. Rabi Professor of Physics
Columbia University
New York, NY 10027

https://blogs.cuit.columbia.edu/waz1/
—————————————————

====================================================================================================

   8:   "will collect approximately 200 PB of data over three run periods utilizing a finite-sized computing center”

This reads strangely to me, since I am not aware of any infinite-sized computing centers.

(Please note: I am trying to be snarky here, just conveying why it caught my eye.)

Perhaps the sentence could be broken up along the lines of

“...will collect approximately 200 PB of data over three run periods. In order to make optimal use of available computing resources…”

 16: “5 second” —> “5 seconds”

 30: “Nuclear Physics” —> “Nuclear Science”

(a sensitive point for some people in the community)

 58: Suggest dropping “finite-sized”, as per above remarks.

 65: “detector hit occupancies  . . . O(100,000)” 

I am not sure what this means. This does not mean a change is required, just noting it’s not clear to me. I am used to expressing occupancies in percentage of available channels. Here you seem to be using it to express the number of discrete chunks of information per event (per crossing?). 

118: “approximately less than” sounds odd, suggest dropping “approximately” or replacing by “less than $\sim 1.2$%.”

Figure 2: Viewing the TPC in Mac Preview on my large monitor is not very informative - any possibility to adjust the shading?

164: If you have space, it would be interesting to describe how 3 degrees, rather than 1 or 10 degrees, was chosen. Presumably it was via some optimization based on pad plane segmentation, expected r-phi resolution, etc. 

185: First mention of Fun4All, reference?

Figure 3: “serves as a wrapper to that interfaces”       Drop “to”?

198: I know you won’t be able to revise this in time for the submission, but it seems somewhat odd after the previous discussion of > 1000 particles per event (not to mention pile-up) to present a result for 100 pions. I guess this is a proof of principle, but wonder how this degrades in the presence of higher multiplicities, kaon decays, hyperon decays, etc.

I do see this noted on line 235 regarding ongoing work, so please treat above as a comment rather than a suggestion for change. 

243: per MB or per central event?

Which raises the question - How does the time scale with the number of tracks? 

Figure 5: Not many in the readership will know what a “double sided crystal ball function” is. 

254: Again, the 10 seconds per event raises the question of scaling with the number tracks. 

347 “finite sized” again

CONCLUSION: The readership of CHEP proceedings is more inclined towards details about software than the mission goals of sPHENIX, which are a repeat of what was in the introduction. I suggest a couple of sentences noting a) Factor of 8 improvement in reconstruction time from initial implementation of ACTS, b) utility of the overall ACTS approach. The current conclusion emphasizes that incorporating TPC space-points is “nontrivial”, and I have every reason to believe this is the case, but in the interest of continuing good relations with the ACTS developers perhaps you could note that “while nontrivial, was made possible by the flexibility and uniform implementation of the ACTS tools” or anything else that makes it clear that the sPHENIX experience with moving to ACTS is a positive one. 

On May 11, 2021, at 2:27 PM, Osborn, Joe <osbornjd AT ornl.gov> wrote:

Hi all,

 

Attached is a draft of the tracking paper that is based on the proceedings I submitted to the CHEP conference. I implemented the reveiwer’s comments which were helpful and improved the paper; we will presumably get completely new reviewers once the paper is submitted. 

 

The target journal for submission is Computing and Software for Big Science. Please check your affiliation/name/etc to ensure that it is correct.

 

Please send any comments you might have by one week from today, that is, by May 18^th. This will give me a few days to implement the comments and then send the draft to the collaboration by May 23, which will then give us a few days before submission deadline to address any additional comments.

 

 

Joe Osborn

 

---------------------------

 

Joe Osborn, Ph.D.

Postdoctoral Research Associate

Oak Ridge National Laboratory

osbornjd AT ornl.gov

(859)-433-8738

 

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Dennis V. Perepelitsa

Assistant Professor, Physics Department

University of Colorado Boulder