sPHENIX bulk physics topical group

[Ron Belmont <belmonrj AT gmail.com>]

Hi All,

Many thanks for the very lively and engaging discussion today.  Meeting minutes are attached below; see also the agenda page.  Please feel free to send me any corrections if you find a mistake.

Regards,

Ron

Hao-Ren, multiplicity analysis with tracklets

Slide 2
Question: How is centrality categorized for these results?
Answer: Forward hadron multiplicity
Question: Is it possible to work around the autocorrelations and use the central barrel multiplicity as the centrality measure?
Answer: Possibly, but reluctant to make such a dramatic departure from previous measurements

Slide 5
Comment: Of order 10^4 events is sufficient for a measurement; 10^5 events as used by LHC experiments yields approximately zero statistical uncertainty

Slide 7
Clarification: rho_n is the radial distance from the beam pipe to the nth layer of the MVTX, so it's the same for all clusters in a given layer

Slide 9
Question: What is the cause of the off-diagonal events?
Answer: Unknown, will study.
Comment: Likely from very very low multiplicity events, not yet clear how far peripheral we want to go for this measurement
Question: Status of simulations with no pileup?
Answer: Request has been made to Chris
Question: Is the no pileup simulation less realistic?
Answer: There may some very low luminosity running initially. Alternately, it may be possible to request low luminosity running at the end of a store
Comment: Higher luminosity running would necessitate the use of the INTT to get vertex separation
Question: How are truth vertices counted? Use negative embed ID?
Answer: Just count the number of truth vertices in the tree.
Comment: Might be interesting to compare the negative embed ID to the simple count.

Slide 10
Comment: Would be nice to see the evolution of the width in eta as a function of multiplicity

Slide 12
Question: Why is the eta distribution asymmetric?
Answer: The z-vertex distribution in the simulation is asymmetric (see backups, slide 43)
Comment: There may be some bias in the z-vertex distribution during real data taking, corrections would need to be worked out

Slide 15
Question: Are the alignment offsets of 10um, 50um, 100um realistic?
Answer: Yes, realistic. A mis-alignment on the order of 1 mm or more would be a major problem

General discussion
Question: Can use off-center collisions to get large acceptance?
Answer: In principle yes, but planning to focus on consistency with previous measurements
Comment: Ideal analysis for day-1, as it demonstrates a lot of systems working correctly (MBD and MVTX timed in, DAQ operating, data can be reconstructed, etc) but is still a simpler analysis than something requiring e.g. full tracking.

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Ron Belmont (he/him/his)
Past Chair, RHIC/AGS Users' Executive Committee
Assistant Professor, Department of Physics & Astronomy
University of North Carolina at Greensboro
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On Aug 15, 2022, at 10:08 AM, Ron Belmont <belmonrj AT gmail.com> wrote:

Hi All,

A reminder that we’ll have a TG meeting tomorrow at 9am EDT.

Agenda page: https://indico.bnl.gov/event/16640/

Zoom room: https://bnl.zoomgov.com/j/1613525277?pwd=TExaWUJYUHJMcERCV2ZLQW1OajExZz09 

Regards,

Ron

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Ron Belmont (he/him/his)
Past Chair, RHIC/AGS Users' Executive Committee
Assistant Professor, Department of Physics & Astronomy
University of North Carolina at Greensboro
-----------------------------------------------------------------------------

On Aug 12, 2022, at 11:05 AM, Ron Belmont <belmonrj AT gmail.com> wrote:

Hi All,

We’ll have a Bulk TG meeting this coming Tuesday, August 16 at 9am EDT.  So far we are expecting an update on the multiplicity with tracklets analysis from Hao-Ren, and other updates are welcome.  Please let me know if you’d like to present.

Agenda page: https://indico.bnl.gov/event/16640/

Zoom room: https://bnl.zoomgov.com/j/1613525277?pwd=TExaWUJYUHJMcERCV2ZLQW1OajExZz09 

Regards,

Ron