sPHENIX tracking discussion

["Osborn, Joe" <osbornjd AT ornl.gov>]

Dear sPHENIX tracking enthusiasts,

We received a positive report and acceptance of the Acts tracking paper that was submitted to Computing and Software for Big Science, pending changes suggested by the reviewers. The original email from the editor is shown below with the relevant comments. I have implemented the requested changes and drafted a set of responses to the editor and reviewers. Attached to this email are an updated draft as well as a diff file that shows the changes since the original submission. If you prefer to view the draft on overleaf, the read link can be found here. The proposed responses to the reviewer comments can be found at the following google doc.

The editor has noted that there is a resubmission deadline of Friday, September 17th. Therefore, please let me know by Friday, September 10th, if you have any comments on the updated draft or proposed responses.

Thanks,

Joe Osborn

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

Joe Osborn, Ph.D.

Associate Research Scientist

Oak Ridge National Laboratory

osbornjd AT ornl.gov

(859)-433-8738

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

CC: ian.bird AT cern.ch, simone.campana AT cern.ch

Dear Dr. Osborn,

We have received the reports from our advisors on your manuscript, "Implementation of ACTS into sPHENIX Track Reconstruction", submitted to
Computing and Software for Big Science

Based on the advice received, I have decided that your manuscript can be accepted for publication after you have carried out the corrections as suggested by the reviewer(s).

Below, please find the reviewers' comments for your perusal.
You are kindly requested to also check the website for possible reviewer attachment(s).

While submitting, please check the filled in author data carefully and update them if applicable - they need to be complete and correct in order for the revision to be processed further.

When submitting your revised manuscript, you are kindly requested to provide at the same time your detailed answers to all points raised by the reviewers (and/or by the journal editor handling your paper).
In addition, please submit a "diff PDF" (or similar) to allow for easy comparison and change tracking between the original and revised versions of your manuscript.

Please submit your revised manuscript by accessing the Editorial Manager.

Your username is: osbornjd
If you forgot your password, you can click the 'Send Login Details' link on the EM Login page at https://www.editorialmanager.com/csbs/

I am looking forward to receiving your revised manuscript
before 17 Sep 2021.

With kind regards,
Ian Bird
Lead Guest Editor
Computing and Software for Big Science

Comments to the author (if any):
Reviewer #1: The paper describes the implementation and performance studies of the sPHENIX track reconstruction with the ACTS toolkit. As such it contributes to the demonstration of the viability of a general tracking toolkit for multiple experiments. A novel component is the implementation of the time projection chamber (TPC). Challenges are identified and it is good to see that the authors are working on them. The paper is well written and I recommend to accept it for publication after considering the following comments.

On the first page, right column, first sentence, I suggest to write "the high occupancy of heavy ion collision events".

The bottom picture in Figure 2 is to large extend just grey and one cannot see anything there. Improvements of the display should be considered, e.g. a zoom to the upper right quadrant.

On page 3 the integration times for MVTX and TPC are given as 8 µs and 13 µs and said to be larger than the bunch spacing. For equal bunch spacing a collision rate of 50 kHz would correspond to 20 µs. Could you explain in the paper, how the numbers fit with your statement?

At the beginning of page 5 you say that some inefficiency comes from the minimum pT threshold. Why is this not covered by the definition of the efficiency, requiring 3 hits? Do you have cases with multiple hits of the same track in the same layer?

On page 5, line 23 I suggest to write "The seeds" instead of "These seeds" as you talked about inefficiencies before.

Is it planned to make your implementation of a TPC available in ACTS so that it could be used by others? If not, can you discuss the reasons in the paper?

How does the tracking performance (in terms of efficiency, fake rate, resolution, hit efficiency) compare with your previous track reconstruction algorithm? It would be interesting to know if the faster execution comes with a degradation of physics performance or not.

Do you have a breakdown of the execution time to see where the largest potential is?



Reviewer #2: Thanks for the well-written paper describing an ambitious software development project on a tight timeline.

General comments:
 It may be good to discuss briefly the impact on sPHENIX Physics program if the track reconstruction time were to remain 10sec/event or even increase as the tracking becomes more realistic (space charge, alignment, etc)
 It would be good to know also the purity/fake rate for your seeding algorithms.


Specific comments:
Page 3 line 30 monolothic -> monolithic
Page 4 section 3.1: are you or anyone in the ACTS community working on a long-term solution to handle TPC volumes "natively"?
Figure 5 and 6: why did you simulate 100 pion events if a typical Au+Au collision has 1000 tracks? How would these plots look with 1000 pions? Is the track density in jets a source of concern?
End of page 5/top of page 6. Do you know the reason for the "real loss of efficiency" you mention?
Page 6 line 39. How do you define"mutual edges" Are these edges shared by two triplets one going inside-out and the other outside in?
Page 6. Is there an efficiency plot like the one of Figure 5 for TPC track seeding?
Section 3.3:
what is the relative timing of TPC vs MVTX track seeding algorithms?
How does the time needed to reconstruct an event depend on the track seed purity?
Are there any plans to run track seeding on GPUs like ALICE does?





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